Rocky Reach Dam: Operational and Structural Total ... · Rocky Reach Dam: Operational and Structural Total Dissolved Gas Management by Michael L. Schneider and Steven C. Wilhelms

Rocky Reach Dam: Operational and Structural

Total Dissolved Gas Management

by

Michael L. Schneider and Steven C. Wilhelms U.S. Army Engineer Research and Development Center

3909 Halls Ferry Road Vicksburg, MS 39180

For

Chelan County Public Utility District No. 1 327 N. Wenatchee Ave., PO Box 1231

Wenatchee, WA 98807

Draft Rocky Reach Dam June 29, 2005 TDG Exchange Assessment

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Table of Contents Table of Contents............................................................................................................ 2 List of Tables .................................................................................................................. 3 Preface ............................................................................................................................ 6 Background..................................................................................................................... 7 Objective......................................................................................................................... 7 Approach ........................................................................................................................ 7 Project Description.......................................................................................................... 9

General TDG Exchange Description.......................................................................... 10 Forebay ................................................................................................................. 11 Spillway ................................................................................................................ 11 Powerhouse Flows................................................................................................. 12 Stilling Basin......................................................................................................... 12 Tailwater Channel ................................................................................................. 13 Mixing Zone Considerations.................................................................................. 14

Rocky Reach TDG Exchange Update............................................................................ 14 Results ...................................................................................................................... 16

TDG Loading ........................................................................................................ 18 Alternatives to Manage TDG......................................................................................... 21

Maximize Powerhouse Flows. ................................................................................... 21 Spill from Gates 2 through 12.................................................................................... 23 Spillway Deflectors................................................................................................... 25 Entrainment Cutoff Wall ........................................................................................... 29 Raised Stilling Basin Floor........................................................................................ 33 Raised Tailrace Channel............................................................................................ 36 Raised Stilling Basin with Deflectors ........................................................................ 38 Raised Tailrace with Deflectors................................................................................. 38 Remove Nappe Deflectors......................................................................................... 42

Conclusions and Recommendations .............................................................................. 43 References .................................................................................................................... 48 Figures .......................................................................................................................... 50 Appendix A................................................................................................................... 51


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List of Tables Table 1. Total Dissolved Gas Saturation estimate as a function of structural alternative,

spill policy, river flow, and background TDG saturation for Rocky Reach Dam .... 22 Table 2. Total Dissolved Gas Saturation estimate as a function of structural alternative,

spill policy, river flow, and background TDG saturation for Rocky Reach Dam .... 23 Table 3 Total Dissolved Gas Saturation estimate as a function of structural alternative,




spill policy, river flow, and background TDG saturation for Rocky Reach Dam .... 42


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Table of Figures

Figure 1. Aerated spillway flow at Rocky Reach Dam, May 2, 2002. .......................................50 Figure 2. Aerial view of the Rocky Reach powerhouse and spillway. .......................................51 Figure 3. Profile view of Rocky Reach spillway and stilling basin (section S3 profile). ............52 Figure 4. Plan view of Rocky Reach spillway and stilling basin. ..............................................53 Figure 5. Rocky Reach tailwater channel bathymetry. ..............................................................54 Figure 6. Near-field TDG sampling stations at Rocky Reach Dam. ..........................................55 Figure 7. TDG instrument deployment at Rocky Reach Dam, April 26-May 2, 2002................56 Figure 8. TDG saturation for left bank or spillway side station and project operations at Rocky

Reach Dam, April 29-May 2, 2002....................................................................................57 Figure 9. Total Dissolved Gas Saturation at stations FOP1 and SBP1 during April 26-May 3,

2002 (Includes spill events with a duration of at least 1 hr excluding uniform spill over bays 9-12). ........................................................................................................................58

Figure 10. Maximum TDG saturation below the stilling basin at station SBP1 as a function of total spill flow, Rocky Reach Dam, April 26-May 3, 2002.................................................59

Figure 11. Maximum TDG saturation below the stilling basin at station FOP1 as a function of total spill flow, Rocky Reach Dam, April 26-May 3, 2002.................................................60

Figure 12. Rocky Reach hourly operations and observed TDG saturation at stations SBP1. FOP1, FB, RRDW and Transect LD, April 26-May 3, 2002. (note: LD-avg was determined by flow weighting TDG levels from five stations and LD-calc was based on a mass conservation statement with no added mass component)...........................................61

Figure 13. Rocky Reach hourly operations and observed TDG saturation at stations SBP1, FOP1, FB, RRDW and Transect LD, April 26-May3, 2002. (note: LD-avg was determined by flow weighting TDG levels from five stations and LD-calc was based on mass conservation statement with an added mass component equal to a fraction of the generation discharge)..........................................................................................................................62

Figure 14. TDG saturation at the loading dock (LD) transect and project operations at Rocky Reach Dam, April 30-May 1, 2002....................................................................................63

Figure 15. Spillway flow deflector and stilling basin circulation pattern. ..................................64 Figure 16. Total dissolved gas saturation as a function of specific spillway discharge at Rocky

Reach and Lower Granite Dams (Note: LWG-RSW Lower Granite spill pattern with removable spillway weir, LWG-STD Lower Granite spill with standard spill pattern) .......65

Figure 17. Aerial view of the Rocky Reach powerhouse and spillway with entrainment cutoff wall ...................................................................................................................................66

Figure 18. Total Dissolved Gas Saturation in Spillway Flows as a function of Stilling Basin Depth at The Dalles Dam and Rocky Reach Dam (TDA-JP The Dalles Dam Juvenile Spill Pattern 2000, RRH-STD Rocky Reach Dam Standard Spill Pattern 2002, RRH U9-12 Rocky Reach Dam Uniform Spill Pattern over bays 9-12, 2002)........................................67

Figure 19. Total Dissolved Gas Saturation as a function of Tailwater Channel Depth at Rocky Reach, Ice Harbor, and The Dalles Dams, (RRH standard pattern 2002, IHR Standard and Bulk Pattern, 2004, TDA Juvenile patter 2000) .................................................................68

Figure 20. Tailwater Elevation versus Total River Flow at Rocky Reach Dam, 2002................69


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Figure 21. Total Dissolved Gas Saturation as a function of Specific Spillway Discharge at Rocky Reach and Ice Harbor Dams, (RRH standard pattern 2002, IHR Standard and Bulk Pattern, 2004)....................................................................................................................70

Figure 22. Aerial view of the Rocky Reach powerhouse and spillway with a raised tailrace channel..............................................................................................................................71


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Preface Public Utility District No.1 of Chelan County (Chelan PUD) funded the work described in this report. The authors would like to thank Steven Hays of Chelan PUD for his assistance in implementing the project. Any questions or comments regarding this document can be addressed to Mike Schneider 541-298-6872 or Steve Wilhelms 601-634-2475. Email: [email protected]


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Background In the Columbia River Basin, the day-to-day operation of dams must protect salmonids listed under the Endangered Species Act. A principle means of protecting juvenile salmonids is by providing an alternative passage route to hydroturbines. These alternative passage routes can include bypass or collection channels or passage in spillway releases. A consequence of spilling water is an increase in total dissolved gas supersaturation (TDG) that can be harmful to fish. Elevated levels of TDG are created by the entrainment of air in spillway releases that plunge deeply into the stilling basin and adjoining tailwater channel. The regional resource and regulatory agencies have established numeric criteria limiting both the duration and magnitude of TDG supersaturation associated with voluntary spillway operations in the Columbia River basin. The original 50-year license to operate the Rocky Reach Project expires in the year 2006. The decision to re-license a project is made by the Federal Energy Regulatory Commission and must contain a 401 water quality certification from the state of Washington demonstrating that the project will meet applicable water quality requirements. Chelan PUD has been active in developing a water quality management plan to meet applicable water quality requirements in the State of Washington. This plan documents current programs and proposed actions that will meet the TDG requirements of the Washington State water quality standards. Chelan PUD has tasked the US Army Corps of Engineers, Engineer Research and Development Center (ERDC) to provide a technical assessment of alternative operational and structural that may be applicable to the Rocky Reach Project should additional control of TDG be needed to meet water quality standards.

Objective The objective of this study is to present a technical assessment of potential operational and structural alternatives at Rocky Reach Dam that could be used to manage total dissolved gas supersaturation in the Columbia River generated by project operations. These alternatives may be used to help Chelan PUD meet TDG standards below Rocky Reach Dam, especially during the high flow season. TDG production for each identified alternative is evaluated based on comparisons to structures at other dams with similar hydraulic conditions and through the application of principles governing total dissolved gas exchange. Based on these assessments, alternatives are ranked regarding their TDG performance characteristics.

Approach The total dissolved gas exchange at a hydraulic structure involves the complex interaction between two fluids: air and water. The detailed understanding of this interaction, in terms of mass transfer, is in an elemental phase. Highly descriptive computational fluid dynamic models of gas transfer in a stilling basin are in early stages of development (Orlins and Gulliver, 2000). One means of identifying prospective TDG abatement measures at a dam is through the collection of detailed field measurements over a range of project operations. These study finding can then be compared to similar observations


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at other projects to assess the potential benefits of operational and structural TDG abatement measures. The gas exchange processes observed during the 2002 near-field TDG exchange study at Rocky Reach Dam (Schneider, 2003) provide the basis for identifying and assessing the potential benefits of structural and operational TDG abatement measures for this study. Operational measures, such as spill magnitude, pattern, and powerhouse loading that influence TDG exchange at Rocky Reach Dam, are specifically evaluated to determine their potential level of TDG reduction. Where possible, mathematical descriptions are provided for TDG exchange at a transect near the juvenile fish outfall, which has been identified by the Washington State Department of Ecology as the compliance location for non-fish spill in the Mid-Columbia River TMDL for TDG. This includes a description of the TDG exchange in spillway releases and the contribution from powerhouse flows to the TDG loading on this sampling transect. The potential TDG abatement benefits associated with proposed operational and structural alternatives are further defined through a comparison with the TDG exchange characteristics at other projects that have applied one or more TDG abatement techniques. For instance, if a project is comparably configured to the Rocky Reach Spillway, but has added spillway flow deflectors, then this provides evidence regarding the potential TDG performance associated with the installation of deflectors at Rocky Reach. However, site specifics differences between projects and an understanding of TDG exchange processes must be carefully factored into these comparisons between projects. A technical assessment of the TDG management potential of the proposed structural and operational alternatives outlined in Table 3 of Chelan PUD’s water quality management plan, which are based on a report prepared by (MWH, 2003). This technical assessment focuses on the alternatives recommended for further evaluation. A review of the TDG exchange properties at Rocky Reach Dam indicated that an additional alternative was warranted for consideration for TDG abatement in this study. This additional alternative involves the consideration of an entrainment cutoff wall to partition powerhouse flows from the highly aerated spillway flows. The list of alternatives reviewed by this study is as follows:

1. Maximize Powerhouse Flows 2. Spill from Gates 2 through 12 3. Spillway Deflectors 4. Entrainment Cutoff Wall 5. Raised Stilling Basin 6. Raised Stilling Basin with Deflectors 7. Raised Tailrace 8. Raised Tailrace with Deflectors 9. Remove Nappe Deflectors


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The potential TDG characteristics, associated with these alternatives, are developed given the current understanding of TDG processes and comparisons to other projects. Alternatives are ranked based on their projected TDG performance.

Project Description Physical Configuration. Rocky Reach Dam is located at river mile 473 on the Columbia River about seven miles upstream from the city of Wenatchee, WA. The Rocky Reach pool extends 43.0 miles upstream to Wells Dam and typically contains 387,500 acre-ft of gross storage capacity. As a run-of-the-river hydroelectric facility, the Rocky Reach Project has limited useable water storage capacity (36,000 acre-ft) as the forebay water surface elevation1 ranges from 703 to707 feet above mean sea level. The tailwater elevation is normally about 619 feet and varies primarily in response to total river flows. Rock Island Dam is situated about 20.3 miles downstream of Rocky Reach Dam and receives flow from operations at Rocky Reach Dam and from the Wenatchee River. Rocky Reach Dam is owned and operated by the Chelan County PUD. The dam is an L-shaped reinforced concrete structure 2,003 ft in length consisting of a powerhouse oriented parallel to the river banks and angled about 95 degrees to the spillway section, as shown in Figure 1. The powerhouse is 1,088 ft long and consists of 11 adjustable-blade Kaplan turbines with a rated output of 1,292 (MW) and a maximum hydraulic capacity of 220 thousand cubic feet per second (kcfs). The turbines are numbered consecutively from south to north with the higher numbered units closest to the spillway as shown in Figure 2. The Kaplan turbines and governors for units 8-11 are of larger capacity than the original turbines in units 1-7. The maximum discharge through the higher capacity turbines is 21 kcfs compared to 17.5 kcfs for the older units. The spillway has a total length of 740 ft and consists of 12 bays, each of which is controlled by a 58-ft high radial gate. The nominal width of each bay is 50 ft and the adjoining piers are 10 ft in width. The spillway crest is located at elevation 650 or about 57 ft below the normal upstream water-surface elevation (Figure 3). The spill bays are numbered in increasing order from west to east (Figure 2). The stilling basin at Rocky Reach Dam is unique to the Columbia River basin. This unique design was necessitated by the need to efficiently dissipate energy over a relatively short distance. Spill bays 2-12 have a notched nappe deflector that is a horizontal bench beginning at elevation 645 but transitioning to a slightly negative angle from horizontal as shown in Figure 3. The notched section, about 12 feet in width at the end of the bench, is a continuation of the gradually increasing slope defining the spillway face. The notched section for bay 2 has a raised wedge resulting in a shallower centered step. Aeration wedges, triangular blocks located adjacent to the spillway piers, were located at piers 2, 4, 9, 10, and 14. The first spill bay does not have a nappe deflector but has a positive sloped deflector located at the base of the spillway face.

1 Elevations cited herein refer to the National Geodetic Vertical Datum


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The stilling basin is subdivided by a fish ladder located between spill bays 8 and 9,and a training wall located between bays 1 and 2, as shown in Figure 2. The stilling basin has a continuous stilling basin impact sill located about 70 ft downstream from the end of the nappe deflectors in bays 2-12. The location and elevation of the impact sill and stilling basin floor vary between four different designs as shown in Figure 4. The deepest stilling basin, (labeled S5 in Figure 4), has an invert elevation of 582 and an average elevation of 593.7. The stilling basin depth has been found to be an important determinant of TDG exchange at many projects such as The Dalles and Ice Harbor Dams. The shallowest stilling basin area, (labeled S4 in Figure 4), has an invert elevation of 590 and an average elevation of 598.4. The stilling basin areas S2 and S3 have an invert elevation of about 585 and an average elevation of 595.7 . The average stilling basin elevation was estimated by integrating the elevation between the upstream end of the stilling basin, which was associated with a tailwater elevation of 620, and the end sill. A notched, sloping (50 degree) end sill was located at the end of the stilling basin about 150 ft downstream of the nappe deflector. The notched section of the end sill is about 6 ft wide at an elevation of 607. The raised section of the end sill is about 14 ft wide with an elevation of 615. The channel bed elevations within 300 ft of the stilling basin are important because highly aerated flow extents throughout this region. The channel bed just downstream of the end sill ranged in elevation from el 586.5 to el 600 as shown in Figure 4. The tailwater channel bathymetry within 250 ft of the stilling basin is generally uniform, at elevations ranging from 580 to 590, with the exception of a deep hole centered on the pier between spill bay 7 and 8 with a minimum elevation of 572. Elevations above 590 along the left channel bank encroach on the area downstream of spill bay 12. The tailrace channel is generally deeper than conditions in the stilling basin. The general topographic features of the Columbia River below Rocky Reach Dam are important in defining the lateral flow distribution and downstream mixing zone between powerhouse and spillway releases. The Columbia River from the Rocky Reach Dam to the Highway 97 Bridge is nearly straight heading in a south to southeast direction. The tailwater channel bathymetry within a mile of the dam has a width ranging from about 700 to 1,200 ft and an average cross-sectional depth ranging from 25-35 ft. The Columbia River channel bathymetry over a 1.25-mile reach below the Rocky Reach Dam is shown in Figure 5. The channel thalweg is near mid-channel immediately downstream from the dam and migrates to the left side of the channel at the first significant channel constriction. General TDG Exchange Description This section describes processes governing TDG exchange at spillways and powerhouses, based on studies at main-stem dams on the Columbia and Snake rivers. Similarities are drawn between these general processes and the existing TDG exchange properties at Rocky Reach Dam. The gas exchange characteristics of a structure are closely coupled to the project hydrodynamics and entrainment of air. Without the entrainment of air


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bubbles, the exchange of atmospheric gases at a hydraulic structure is restricted to the water surface where gas exchange tends toward equilibrium at 100 percent of saturation. With aerated flow at a dam due to surface aeration, plunging action, or induced aeration, the gas exchange process can quickly become dominated by the entrained bubbles (Wilhelms and Gulliver 1994). If bubbles are transported to depth (even as little as three to four feet), the hydrostatic pressure compresses the bubbles thereby increasing their gas concentrations above atmospheric. This allows the transfer between entrained air and the water column to levels above atmospheric, causing TDG supersaturation. These elevated total dissolved gas pressures cannot be maintained in a non-aerated flow environment, where gas transfer at the water surface tends to reduce supersaturated conditions back to equilibrium at 100 percent saturation. However, at depth the gas remains in solution due to hydrostatic pressure, resulting in the retention of elevated TDG levels in the river. Two general principles are applicable to TDG management alternatives: 1) eliminate or reduce the entrainment of air and 2) minimize the depth to which entrained air is transported. The following description of TDG exchange at different regions of a project is based in part on the near-field TDG studies conducted during the dissolved gas abatement study conducted for federal dams on the Columbia and Snake rivers (USACE 2002). This discussion focuses upon the hydrodynamic and gas exchange characteristics in four regions: forebay, spillway/turbine passage, stilling basin, and tailwater channel.

Forebay The TDG properties in the immediate forebay of a dam are generally uniform, when no thermal stratification or surface warming is present, although they can change rapidly in response to operations of upstream projects, tributary inflows, and meteorological, and limnological conditions. A small vertical temperature gradient of 3 to 4 oF can limit the influence of gas exchange at the water surface to the near-surface layers of a pool by inhibiting vertical circulation. Additionally, heating of surface water can cause TDG pressure responses that result in changes to supersaturated conditions because the solubility of a gas in water decreases as water temperature increases (Colt 1984). Although not likely a significant component in the Columbia River at Rocky Reach Dam, biological activity involving the production or consumption of oxygen may also influence TDG pressure. Thus, under stratified conditions, the initial TDG pressure of spillway releases may be different from those associated with hydropower releases, depending upon the level of withdrawal. The flow under a spillway gate or into a turbine intake may spawn vortices or other local hydraulic conditions that provide a vehicle for air entrainment. In general, however, TDG contributed by these local phenomena is insignificant.

Spillway The depth of flow and water velocities change rapidly as flow passes under the spillway gate onto the face of the spillway. The roughness of the spillway piers and gates may generate surface turbulence and water spray that entrain air. Flow on the spillway may


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become aerated for low specific discharges2 as a consequence of the development of the turbulent boundary layer. However, the short time of travel down the spillway will limit the exposure of water to entrained air bubbles to only a few seconds and tend to limit the absorption or desorption of TDG (Rindels and Gulliver 1989, Wilhelms 1997). At some projects in the Columbia River Basin during forced spill conditions where forebay TDG levels are elevated, the entrained air, shallow flow on the spillway, and stilling basin conditions combined to reduce the net loading of TDG in the river. At Rocky Reach, aeration devices on the spillway add air to reduce the potential for cavitation damage and generally improve the flow conditions. These aerators likely increase the air entrainment in the spillway releases; however, the physical exchange processes in the stilling basin and tailrace – that is, the forcing into solution of entrained air in the stilling basin and the stripping of dissolved gas in the tailrace – dominate the TDG levels in spillway discharges, making the ultimate release of TDG independent TDG levels in the forebay or generated on the face of the spillway.

Powerhouse Flows There is little opportunity for entrained air to be introduced into the confined flow path through a turbine, except during inefficient turbine settings, when air is aspirated into the turbine (Wilhelms, Schneider, and Howington 1987). During normal turbine operation, there is essentially no change in TDG pressure as power generation flows pass through the powerhouse. Since turbine discharges typically do not entrain air, it has generally been observed that generation discharges pass forebay TDG pressures to the downstream pool and do not directly contribute to higher TDG loading (CENPD 1998). The proximity of powerhouse releases to the high-energy environment in the stilling basin can result in a strong interaction of these project discharges. If the powerhouse flows are sufficiently isolated from the stilling basin action, then the fate of powerhouse releases is to dilute (due to lateral downstream mixing) TDG pressures produced by spillway releases. However, if the powerhouse releases are completely or partially entrained into the highly aerated flow conditions of the stilling basin, then this flow may experience TDG exchange processes similar to those experienced by spill and thereby reducing or eliminating the potential for downstream dilution. Data from the 2002 spill test seems to indicate that this process occurs at Rocky Reach Dam. During spill patterns not involving spill bay 2, an adverse water surface gradient was present driving a return current into the stilling basin. It is likely that much of this entrained flow originated from powerhouse releases.

Stilling Basin The flow conditions in the stilling basin are highly three-dimensional and are shaped by tailwater elevation, project head, spillway geometry, and the presence of spillway piers, sidewalls, baffle blocks, and end sill. In general, however, the flow conditions

2 Discharge per unit width, cfs per foot


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downstream of a spillway are characterized by highly aerated flow plunging to the bottom of the stilling basin. A bottom current directs flow out of the stilling basin, while a surface roller returns flow back to the plunge point. The influence of the spillway bench is to generate an aerated jet that plunges near the toe of the spillway face and in turn creates an area for flow to return to the face of the spillway. This return flow under the aerated jet interacts with the jet issuing through the center slot providing for an addition mechanism to dissipate energy. The baffle blocks and end sill redistribute the bottom-oriented discharge current throughout the water column. Because of the high air entrainment and the transport of air to full stilling basin depth, a rapid and substantial absorption of atmospheric gases takes place in the stilling basin. These flow conditions result in the maximum TDG pressures experienced below the dam. The TDG in the stilling basin, as well as downstream of the tailrace is dependent upon the specific discharge of the spillway. Previous studies have suggested that stilling basin TDG levels at very low specific discharges may be relatively low, around 120 percent, but rapidly climb with increasing discharge to asymptotically approach a maximum, that depends upon the stilling basin depth. The end sill design at Rocky Reach Dam also distinguishes it from other projects in the Columbia River Basin. The sloped and notched end sill forces aerated flow to be directed toward the water surface. A high velocity jet is formed during flow passage over and through the end sill obtaining a form similar to the surface jet emanating from a spillway flow deflector. A secondary plunge is then formed as this jet issues into the tailwater channel. These flow features associated with passage over the endsill were recorded during physical model testing of the structure.

Tailwater Channel A rapid and substantial desorption of supersaturated dissolved gas takes place in the tailwater channel immediately downstream of the stilling basin (Schneider and Wilhelms 1996). As the entrained air bubbles are transported downstream, they rise above the compensation depth3 in the shallow tailwater channel. While above the compensation depth, the air bubbles strip dissolved gas from the water column. The entrained air content decreases as the flow moves downstream, and the air bubbles rise and escape to the atmosphere. Dissolved gas desorption appears to be quickly arrested by the loss of entrained air within 200 to 500 hundred feet of the stilling basin. The depth of the tailwater channel appears to be a key parameter in determining TDG levels entering the downstream pool. If a large volume of air is entrained for a sufficient time period, the TDG saturation will approach equilibrium conditions dictated primarily by the depth of flow. Thus, mass exchange in the tailwater channel has a significant influence on TDG levels delivered to the downstream pool during high spill discharges.

3 Compensation depth is the depth at which the ambient TDG concentration would be at 100 percent saturation relative to the absolute pressure at that depth. For example, for TDG = 110 percent, relative to atmospheric pressure, the compensation depth is approximately 1 meter, where the absolute pressure is about 1.1 atmospheres.


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The rapid exchange of TDG pressures ceases downstream of the zone of bubbly flow. The exchange of atmospheric gasses continues at the air-water surface driving conditions toward 100 percent of saturation. The TDG pressures generated at a dam can also change rapidly throughout a downstream river reach as the mixing zone develops. As discussed previously, hydropower releases entrained into the aerated spillway flows will often be exposed to similar levels of TDG exchange as experienced by spillway releases, thus influencing the amount of hydropower flow available for downstream dilution in the mixing zone. An understanding of the development of the mixing zone is critical to the interpretation of point observations of TDG pressure in the river. In regions where the mixing between powerhouse and spillway releases are incomplete, lateral gradients in TDG pressure will be present and point observations of TDG pressure will reflect some degree of mixing of project flows. The properties of the mixing zone will be dependent upon the tailwater channel features, the location of powerhouse and spillway structures, hydrodynamic conditions in the river, spillway and powerhouse operations, and the entrainment of powerhouse flows into the aerated spillway flows.

There are a number of processes that can further influence the TDG characteristics in a river reach below a dam. The mass exchange process in the river will continue to restore TDG levels toward 100 percent of saturation. The mass exchange at the water surface can be greatly accelerated where surface waves increase the air-water interface, entrain bubbles, and promote the movement of water to the surface layer. The roughening of the water surface can be generated by surface winds or channel features such as rapids or local flow obstructions. The inflow from tributaries to the main stem can change the water quality properties in the study area through transport and mixing processes. The heat exchange within the river systems can result in rising and falling water temperatures that influence TDG pressures. The interaction of nutrients, algae, and dissolved oxygen (DO) can impact TDG concentrations in a river. The diurnal cycling of photosynthesis and respiration is chiefly responsible for fluctuations in DO concentrations. These in-river processes influence how rapidly TDG levels are altered from conditions generated during spillway operations.

Mixing Zone Considerations. The TDG characteristics of spillway and powerhouse flows exiting Rocky Reach Dam are often quite different resulting in a reach of river where these flows mix called the mixing zone. The interpretation of observations of TDG pressure directly below the dam and extending through the tailwater fixed monitoring station located near the middle of the channel on the highway 97 bridge, will be a function of the rate of development of this mixing zone. The TDG pressure at any one point of sample will be a function of the ratio of spill to powerhouse flow, spill pattern, spill magnitude, and the TDG content of forebay waters. The observations from the 2002 TDG exchange study concluded that the average TDG saturation in the Columbia River at the tailwater fixed monitoring station was about one percent saturation higher than the response at the tailwater fixed monitoring station (RRDW).

Rocky Reach TDG Exchange Update

The objective of this study component is to develop a technical assessment of operational and structural alternatives at Rocky Reach Dam to reduce TDG supersaturation in the Columbia River generated by project operations. These alternatives may be applicable to


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Rocky Reach Dam should Chelan PUD need to implement additional measures to continue to meet State and Federal TDG standards below Rocky Reach Dam, especially during the high flow season.

A detailed investigation of total dissolved gas exchange at Rocky Reach Dam was presented in a report entitled “Total Dissolved Gas Exchange During Spillway Operations at Rocky Reach Dam, April 26-May 3, 2002” (Schneider, 2003). During this investigation, an array of TDG instruments was deployed both above and below Rocky Reach Dam during April 26 - May 3, 2002. Routine and alternative project operations were scheduled during this time period to quantify the TDG exchange properties associated with spillway operations. The spillway flow ranged from 10.6 kcfs to 61.0 kcfs during the study period. Spillway operations at Rocky Reach Dam increased the TDG saturation in the Columbia River during the study period. The increase in average TDG saturation in the Columbia River ranged from 1.6 to 8.6 percent saturation as measured across the river on a sampling transect located about 0.7 miles below the dam. The TDG saturation exiting the spillway was found to be a function of the spill pattern, spillway discharge, and to a lesser extent, powerhouse operations. The maximum TDG pressures were observed immediately downstream from the spillway near the left channel bank. The highest TDG saturation observed during the study was 128.9 percent during 61 kcfs spill over bays 2-8. The TDG saturation in spill water was found to be a linear function of spillway discharge for a given spill pattern. Higher powerhouse releases were found to reduce the TDG saturation at stations on the spillway side of the channel. The TDG saturation in spillway releases was observed to change by as much as 5 percent saturation in response to changing powerhouse flows.

The entrainment of powerhouse flows into the aerated spillway releases was

evident through visual observation of surface flow conditions. The TDG loadings observed for Rocky Reach operations were also consistent with these observations. Lateral gradients in TDG saturation were present downstream from the dam at the Highway 97 Bridge where the tailwater fixed monitoring station is located. These lateral gradients became more pronounced for higher spill discharges. The average cross-sectional TDG saturation at the Highway 97 Bridge was generally about one percent saturation greater than measured at the tailwater fixed monitoring station. The maximum TDG saturation on this transect was from 2.5 to 5.5 percent saturation higher than measurements at the station RRHW. During the 2002 TDG exchange study at Rocky Reach Dam, the TDG pressures were sampled on several transects located below the dam with the purpose of measuring temporal and spatial TDG properties in the Columbia River during spillway operations. The location and sampling station abbreviations are shown in Figure 6 and 7. The nearest TDG sampling stations to the stilling basin were stations labeled (SBP1 – SBP3) located about 500 ft downstream of the stilling basin end sill. A second TDG sampling transect (FOP1-4) was located near the juvenile fish outfall within one-half mile of the spillway. Several statistically derived models of TDG exchange were presented in (Schneider, 2003) relating the peak levels of TDG pressure observed below the spillway to project


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operating conditions. The evaluation of the TDG data collected during the 2002 field study focused on the TDG response observed immediately downstream of the spillway at stations SBP1 and SBP2 as shown in Figure 6. This review expands the evaluation of TDG exchange as observed near the left channel bank about 1600 ft below the spillway at a station labeled FOP1. This sampling station was located near the existing juvenile fish bypass outfall. This study component also addresses the computation of net TDG exchange or average TDG loading produced during this study period. The peak and average TDG pressure generated during spillway operations are needed to characterize TDG exchange, alternative structural TDG abatement alternatives, and the habitat associated with acute and chronic exposure of aquatic organisms to TDG supersaturation. Results TDG Exchange at Stations SBP1 and FOP1 The measurement of TDG properties near station FOP1 has several advantageous characteristics. This sampling station shown in Figure 6 is located directly below the spillway and reflects the TDG levels generated in spillway releases. This sampling location was downstream of highly aerated flow conditions generated during spillway releases. The sampling stations labeled SBP1-SBP3 (Figure 6) all encroach upon the region of aerated flow during high spillway flows. The flow conditions at station FOP1 are suitable for maintaining a reliable measure of TDG pressures. And finally, this sampling location is consistent with the guidelines set out in the Mid-Columbia River TDG Total Maximum Daily Load (TMDL).

The highest TDG pressures observed during this study were recorded at station SBP1. The time history of TDG saturations at selected sampling stations and project operations are shown in Figure 8. This figure shows the strong correlation between TDG pressures monitored at stations SBP1 and FOP1. The TDG saturation did not exceed 120 percent at the sampling station FOP1 during the application of the standard spill pattern for spill up to 60 kcfs during this testing period. The instantaneous TDG saturation at stations FOP1 and SBP1, excluding observations during spill events uniformly distributed over bays 9-12 and transitional periods between changes in spillway releases are shown in Figure 9. A linear regression was determined from this data set involving the TDG saturation at stations FOP1 and SBP1 with a slope of 1.05 and an r2 value of 0.97.

Both the standard spill pattern and alternative spill patterns were investigated during

this study as a means of identifying the TDG exchange characteristics of the entire spillway. The standard spill pattern uses gates 2-8 with a minimum discharge per spill bay of about 4 kcfs. The standard spill pattern was designed to create a V-shaped pattern of turbulent flow below the spillway with decreasing velocities leading toward the fishway entrances. This type of spill pattern has been adopted at a number of dams on the Columbia and Snake rivers to provide hydraulic conditions expected to help adult salmon find the fishway entrances. The alternative spill patterns involved uniformly distributed spill over bays 2-5, 5-8, 9-12, 2-8, and 2-12. These alternative spill patterns allowed a systematic variation of the left, middle, and right sectors of the spillway as well as providing for a greater range in the specific spill discharge. A total of 34 specific spill events with duration of at least two hours were


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identified during the study period as a function of spill pattern. The timing of these events is shown in Figure 8. A total of 16 out of the 34 spill events identified in this study involved the standard spill pattern. The alternative spill patterns were scheduled during the study period subject to the volumetric constraints for spring fish spill at Rocky Reach Dam.

The maximum TDG saturation on Transect SB associated with the standard spill pattern was linearly related to the total spill discharge for all the spill events sampled. A linear regression between the event averaged maximum TDG saturation on Transects SB and total spillway discharge was determined for 16 standard spill pattern events and is shown in Figure 10. The TDG saturation was found to increase by about 1.5 percent saturation for an increase in spill discharge of 10 kcfs as shown by Equation 1. The error bars for each observation represents one standard deviation in TDG saturation during the event. The large standard deviation about the mean value for some events was caused by the variation in powerhouse flows during a constant spill event. The linear regression line intercepts 120 percent saturation at a spill discharge of 56 kcfs. The maximum TDG saturation on Transect SB associated with the non-standard spill patterns were all consistently higher than observed during the standard spill pattern with the exception of the uniform spill pattern using gates 2-12. The event averaged TDG response and corresponding linear regression equation for each of the non-standard spill patterns are shown in Figure 10. The uniform spill using gates 2-12 was observed only during two events with results similar to the standard spill pattern.

)1(63.086.061.1111509.0 2

1 ==+= stdspSBP ERQTDG where TDGSBP1 = TDG saturation % at station SBP1 (event averaged) Qsp = Spillway discharge for standard pattern (kcfs) R2 = Coefficient of correlation Estd = Standard error of estimate (%)

The events based TDG response at station FOP1 was also evaluated as a function of

the standard spill for four of the six spill patterns tested during this study period as shown in Figure 11. In each case, the TDG saturation at station FOP1 was linearly related to the total spill discharge. A linear regression between the TDG saturation at station FOP1 was determined for the 16 standard spill pattern events and the TDG saturation was found to increase linearly by about 1.4 percent saturation for an increase in spill discharge of 10 kcfs. The results from the linear regression of TDG saturation at station FOP1 versus spill discharge for the standard spill pattern is listed in Equation 2. This slightly smaller slope in the relationship between TDG saturation and spill discharge yields an extrapolated spillway capacity of 62.7 kcfs at 120 percent of saturation. The TDG saturation associated with the five events with uniform spill patterns was also linearly related to total spill discharge. In general, the TDG response for different spill patterns at station FOP1 was much more consistent than observed at station SBP1. The slope determined from a linear regression between TDG saturation at station FOP1 and spill discharge in kcfs ranged from 0.14 to 0.21.


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The regression equation correlation coefficients were also strong ranging from 0.87 for the standard pattern to 0.97 for the uniform spill over bays 9-12.

)2(65.087.050.1111355.0 21 ==+= stdspFOP ERQTDG

where TDGFOP1 = TDG saturation % at station FOP1 (event averaged) Qsp = Spillway discharge for standard pattern (kcfs) R2 = Coefficient of correlation Estd = Standard error of estimate (%)

TDG Loading The average TDG saturation or TDG loading was established at Transect LD (Figure 7) located about 0.7 miles downstream from the Rocky Reach spillway. This channel location was chosen due to the bathymetric features of the channel, flow conditions, and proximity to project releases. The lateral flow distribution was determined conducting mobile Acoustic Doppler Current Profiling (ADCP) transects over a range of flow conditions. The flow-weighted average TDG saturation was determined using the observed TDG pressure observations at stations LDP1-P5. The flow-weighted average TDG saturation was computed by using Equation 3 which assumes a piece-wise uniform distribution of flow and TP.

tot

LdPLdPLDPLDPLDPavgLD Q

TDGQTDGQTDGQTDGQTDGQTDG 5544322211 ++++

=− (3)

where

TDGLD-avg = flow weighted average TDG saturation on transect LD TDGLDP1-LDP5 = TDG saturation at stations LDP1-LDP5 Qtot = Total river flow Qi = sector discharge 1-5

The time history of the average observed TDG saturation on Transect LD is shown in Figure 12 throughout the study period and is labeled as LD-avg. The difference between the average TDG saturation in the Rocky Reach forebay (FB) and on the transect LD (LD-avg) reflects the net increase in average TDG saturation caused by spillway releases at Rocky Reach Dam during the study period. A simple mass conservation statement can be developed for computing the flow-weighted average TDG saturation exiting the dam by associating a TDG saturation with the powerhouse and spillway flows as shown in Equation 4.


19

tot

gengenspspavgLD Q

TDGQTDGQTDG

+=− ……………………………………….(4)

where:

Qtot = Total River Flow (kcfs)

Qsp = Spillway discharge (kcfs)

Qgen = Generation discharge (kcfs)

TDGgen = TDG saturation of generation discharges (percent)

TDGavg = average TDG saturation on transect LD (percent)

TDGsp= TDG saturation of spillway discharges (percent)

For this calculation, the average TDG pressures observed at station FOP1 were assumed to be representative of spillway releases (TDGsp) undiluted by powerhouse flows and that the TDG pressures observed at station FB were representative of all powerhouse flows. This approximation assumes the fate of all the powerhouse releases is to dilute the TDG pressures generated in spillway discharges. The flow-weighted average TDG saturation (LD-cal) estimated from the observations immediately below the dam using Equation 4 were significantly less than the average observed TDG saturation at the LD transect calculated using Equation 3 throughout the study period as shown in Figure 12. In general, the calculated average TDG saturation under-estimated the observed average TDG saturation by 1 to 2 percent saturation. To account for the added TDG loading observed at the LD transect, an added mass term was included in the conservation statement as shown in Equation 5. This added mass discharge is similar to a powerhouse flow entrainment term where a portion of powerhouse release encounters the aerated flow conditions caused by spillway flows and experiences a similar level of TDG uptake. This formulation reduces the amount of flow from the powerhouse releases available for dilution with spillway releases while increasing the volume of water exposed to highly aerated flow below the spillway.

tot

genamgenspamspavg Q

TDGQQTDGQQTDG

)()( −++= (5)

where:

Qtot = Total River Flow (kcfs)

Qsp = spillway discharge (kcfs)


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Qgen = generation discharge (kcfs)

Qam = added mass discharge (kcfs)

TDGgen = TDG saturation of generation discharges (percent)

TDGavg = average TDG saturation on transect USGS (percent)

TDGsp= TDG saturation of spillway discharges (percent)

A simple functional form for the added mass discharge was determined from a least-squares analyses of the instantaneous TDG observations using the forebay TDG saturation (FB) representing powerhouse TDG release levels, station FOP1 representing the TDG content of spillway releases, and observed average TDG saturation on Transect LD reflecting average river conditions. The recorded powerhouse and spillway discharge were also used in the calculation of conditions defined by Equation 5. The added mass discharge was estimated to equal 26 percent of the powerhouse discharge minus 5.46 kcfs as limited by the total spillway discharge as shown in Equation 6. A generation discharge of 80 kcfs will result in an added mass discharge of 15.2 kcfs provided that the spill discharge is greater than 15.2 kcfs. The added mass discharge becomes small as the powerhouse or spillway discharge goes to zero. This relationship was developed for powerhouse flows averaging 105 kcfs and ranging from 23.5 to 178 kcfs during April 26-May 3. Qam = min(Qsp, 0.26*Qph – 5.46) (6) Where 0 < Qam < Qph The observed (Equation 3) and calculated (Equation 5) average TDG saturation on Transect LD was determined using an added mass term as described by Equation 6 for conditions observed during the study period on April 27-May 2, 2002. The time history of the observed flow weighted average TDG saturation (LD-avg) and calculated average TDG saturation (LD-calc) are shown in Figure 13. The inclusion of the added mass loading as defined in Equations 5 and 6 resulted in an improved description of the TDG exchange and loading at Rocky Reach Dam. The average predictive error (observed minus calculated average TDG saturation on Transect LD) for 572 observations was 0.04 percent saturation with a standard error of 0.63 percent saturation. The added mass discharge averaged about 21.6 kcfs during the study period and ranged from 0 to 41 kcfs.


21

Alternatives to Manage TDG Based on the MWH (2003) review, the following alternatives recommended for further evaluation, with the addition of the entrainment cutoff wall:

1. Maximize Powerhouse Flows 2. Spill from Gates 2 through 12 3. Spillway Deflectors 4. Entrainment Cutoff Wall 5. Raised Stilling Basin 6. Raised Stilling Basin with Deflectors 7. Raised Tailrace 8. Raised Tailrace with Deflectors 9. Remove Nappe Deflectors

In the following section, each of these alternatives is described and an assessment of total dissolved gas abatement is presented. Maximize Powerhouse Flows. During normal operations, most of the river can pass through the Rocky Reach turbines. However, in order to improve juvenile fish passage spill maybe required to meet fish passage objectives. For instance, during the spring and summer of 2003, a commitment to spill 15 percent of the river was adopted to aid juvenile migration. During the peak migration of juvenile sockeye, this spill commitment was increased to 25 percent of the river for up to 21 days. Spill levels were reduced in 2004-2005, based on the success of passing yearling Chinook and steelhead with the juvenile fish bypass system. However, spill of 24% of the flow was provided for sockeye passage and 9% of the flow was provided during the summer migration of subyearling Chinook.

The results from the 2002 TDG exchange study verified the hypotheses that the TDG content of water passing through the turbines at Rocky Reach Dam remained constant. The TDG content in the forebay can be applied to the water discharged from the turbines. The fate of powerhouse releases is to either dilute the TDG content in spillway flows or to be entrained into the highly aerated flow conditions generated by spill and to be influenced by this mass exchange process. The gas abatement benefits of reducing the commitment to spill can be estimated by applying the results from equations 1-6 for a range of forebay TDG levels, spill policies, total river flow, and powerhouse capacity. The spill discharge was determined from the larger of the fish passage spill commitment or forced spill requirement (Qtotal-Qph-max). A family of TDG estimates were generated for Rocky Reach Dam for fish passage policies committing 0, 5, 10, 15, 25, and 35 percent of the total river flow to spill. The TDG estimates in spill water and average river conditions below Rocky Reach Dam were determined for three river flows, 150 kcfs, 200 kcfs, and 250 kcfs (7Q10) and five forebay TDG levels, 105, 110, 115, 120, and 125%. To determine forced spill, a


22

powerhouse capacity of 220 kcfs (11 turbines) and 200 kcfs (10 turbines) was also factored into this matrix of conditions. The outcome from all these conditions is summarized in Appendix A, Table A1. A subset of results are listed below in Table 1 for a powerhouse capacity of 200 kcfs, total river flow of 200 kcfs, and a forebay TDG saturation of 110%. A spill commitment of 35 percent will result in a peak TDG saturation in the spillway discharge of 121.0% at the FOP1 sampling location and a flow-weighted average TDG saturation of 115.3% at transect LD for a net increase of 5.3 % saturation above forebay levels. The increasingly smaller commitments to spilling water at Rocky Reach Dam resulted in smaller peak and average TDG levels. A ten percent spill policy will increase the average TDG saturation to 110.8 percent or an increase in average Columbia River TDG saturation of less than one percent. The powerhouse only condition (zero spill) simply passes the upstream TDG levels past the dam.

Table 1. Total Dissolved Gas Saturation estimate as a function of structural alternative, spill policy, river flow, and background TDG saturation for Rocky

Reach Dam

Case Structure

Alternative1

Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs)

Qtotal4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 95 Base 0.00 200 200 200.0 0.0 0.0 110 111.5 110.0 0.0 110 Base 0.05 200 200 190.0 10.0 10.0 110 112.9 110.3 0.3 125 Base 0.10 200 200 180.0 20.0 20.0 110 114.2 110.8 0.8 140 Base 0.15 200 200 170.0 30.0 30.0 110 115.6 111.7 1.7 155 Base 0.25 200 200 150.0 50.0 32.0 110 118.3 113.4 3.4 170 Base 0.35 200 200 130.0 70.0 27.0 110 121.0 115.3 5.3 1 Base-Structural configuration as of 2004 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

The gas abatement benefits of reducing the voluntary spill levels does not extend to conditions where forced spill levels exceeds the targeted voluntary spill policy (Table 2). The forced spill conditions listed in Table 2 results in a net reduction in TDG levels in the Columbia River on the order of 0.7 percent when spilling 50 kcfs during forebay levels of 120%. However, maintaining the voluntary spill level below 25% during high flows does avoid high spill volumes (Table 2, case 162, 177) and resultant high TDG levels.


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Table 2. Total Dissolved Gas Saturation estimate as a function of structural

alternative, spill policy, river flow, and background TDG saturation for Rocky Reach Dam

Case Structure

Alternative1

Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 102 Base 0.00 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 117 Base 0.05 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 132 Base 0.10 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 147 Base 0.15 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 162 Base 0.25 200 250 187.5 62.5 41.4 120 120.0 120.0 0.0 177 Base 0.35 200 250 162.5 87.5 35.2 120 123.4 121.6 1.6

1 Base-Structural configuration as of 2004. 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

Spill from Gates 2 through 12 The specific spillway discharge or discharge per foot of lateral distance, has been found to be an important determinant to TDG exchange at many projects in the Columbia River Basin. This relationship between specific spill discharge and TDG exchange is evident at John Day Dam where the spill pattern chances abruptly from a bulk spill pattern to a uniform spill pattern at 108 kcfs spill. At this transition point in the spill pattern, an increase in total spill discharge causes a reduction in the specific spillway discharge per foot of open gates and a significant reduction in the TDG saturation measured at the tailwater fixed monitoring station. Conversely, a reduction in spill discharge from above 108 kcfs to below 108 kcfs triggers an increase in the specific spillway discharge and a corresponding increase in the spillway TDG content. The mechanism behind the direct relationship between specific spillway discharge and TDG exchange involves the added energy per foot available to entrain air bubble and transport these bubbles to greater depths in the stilling basin. This additional energy can also promote the entrainment of bounding water into the zone of highly aerated flow.

The operating conditions scheduled during the TDG exchange study at Rocky Reach Dam in 2002 encompassed a combination of spillway and powerhouse operating scenarios. Spillway and hydropower discharges were systematically varied to achieve a range of operating conditions while maintaining commitments to hydropower production. A total of 6 different spillway patterns were scheduled during the study period. The standard spill pattern was applied during most of the study period. The standard spill pattern featured the usage of spillbays 2-8. Spillbays 1, and 9-12 where not used during


24

the standard spill patterns scheduled during the study period. The standard spill pattern for flows less than 20 kcfs concentrated spill in bays 4, 6, and 8. Higher spill discharges were achieved by adding bay 2 first, followed by adding odd-numbered spillbays 3, 5, and 7. The minimum spillbay discharge used in the standard pattern was 4 kcfs. This operational constraint stems from the potential damage to gate seals at smaller gate opening. The non-standard spill patterns called for a uniform spill distribution over a designated number of bays. The non-standard spill patterns involved bays 2-5, bays 2-8, bays 2-12, bays 5-8, and bays 9-12. Attempts to correlate TDG exchange with the specific spillway discharge at Rocky Reach Dam were not fruitful. One possible explanation for the lack of a prominent direct relationship between TDG exchange and specific spillway discharge was the duration of constant project operations. The total instantaneous spill discharge was constrained by fish passage agreements stipulating an hourly percent of river to be spilled. A range of spillway discharges could be achieved during a day as the spill discharge varied in accordance with changes in total river flow. While the spill patterns and discharges could generally be held constant for a three-hour duration, the powerhouse discharge rarely remained constant during the same period. The variable powerhouse discharges changed the percent of river spilled at Rocky Reach Dam and resulted in significant changes at most of the downstream sampling stations during a given spill event. This affected the TDG levels in the mixing zone between powerhouse and spillway flows, but did not affect the TDG levels measured at SBP1 and FOP1. The impacts of the specific spillway discharge on TDG exchange was evaluated during a series of two paired events during the 2002 field investigation. The first event involved a uniform 47.5 kcfs spill over bays 2-12 (Event 34) versus a 50.6 kcfs spill over bays 2-5 (Event 27). The primary mechanism, which may lead to differences in TDG exchange for these spill scenarios, involves differences in the mean bubble depth. The widely distributed flow may be influenced more significantly by the shallower flow conditions in the stilling basin. The higher specific discharge events result in highly aerated flow conditions extending well beyond the stilling basin and the associated channel bathymetry may become more important in shaping TDG exchange. The interaction of spillway and powerhouse releases could also influence the TDG exchange associated with these different spill patterns. The TDG saturation associated with a spill of 47.6 kcfs distributed over bays 2-12 on May 2 at 1930 hours were significantly less than the TDG saturation generated during a 50.9 kcfs spill over bays 2-5 on May 1 at 1845 hours. The powerhouse flows for these spill conditions were similar with 106.8 kcfs discharge during the 11-bay spill pattern, and 99.4 kcfs discharge for the 4-bay spill pattern. The 4-bay spill event generated a peak TDG saturation of 124 percent compared with only 119 percent for the 11-bay spill event. The average TDG saturation on transect LD was 113.2 percent during the 11-bay spill event compared 115.5 percent for the 4-bay pattern. The small difference in powerhouse flows is unlikely to account for the differences in TDG saturation observed downstream of Rocky Reach Dam for these conditions.


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The second set of spill events occurred back to back on April 30 between the hours of 1600 and 2400 where a uniform spill of 56 kcfs over bays 2-12 (Event 22) was followed by a spill of 57.8 kcfs using the standard spill pattern (Event 23). The main difficulty in comparing these two events was the difference in the powerhouse discharge. The powerhouse discharge ranged from 72.7 to 102.3 during the 11-bay spill (Event 22) compared to 108.6 to 159.4 kcfs during the standard spill (Event 23). The TDG saturation on transect SB were virtually identical for both events with a maximum TDG saturation of 120.3 percent. The TDG saturation across transect LD during the standard spill pattern was either equal to or greater than the TDG saturation generated during the flat 11 bay pattern as shown in Figure 14. The average TDG saturation for these conditions during the standard pattern was estimated to be 115.5 percent compared to 115.0 percent during the flat pattern. The standard pattern generated a TDG loading greater than the flat pattern even with larger powerhouse flows (17 kcfs) that contained TDG saturations of only 108.5 percent.

The findings from this limited number of test conditions indicates a potential reduction in the average TDG levels of up to 2 percent saturation. This reduction in the TDG loading from Rocky Reach Dam was apparent in the average cross-sectional TDG pressures measured below the dam. The peak TDG levels as observed at station FOP1 were similar for the standard and uniform 2-12 spill patterns sampled during this field study. The uniform pattern may have greater applicability during forced spill events when spillway discharge exceeds 50 kcfs and the powerhouse is fully loaded at about 200 kcfs. The quantitative TDG abatement potential of the 2-12 uniform spill pattern at spill discharges during forced spill events remains to be evaluated. Additional field-testing is recommended to further identify the TDG abatement benefits of applying a uniform spill pattern over bays 2-12. Spillway Deflectors Spillway flow deflectors have been one of the primary methods for TDG management on lower Snake and Columbia River dams (USACE 2002). Ideally, deflectors are positioned on the spillway to redirect flow across the surface of the tailwater. This reduces the plunging action by which the spillway flow transports entrained air to the full depths of the stilling basin. By reducing the mean depth to which entrained air is transported, the level of TDG absorption can be reduced. Spillway flow deflectors have been installed at Bonneville, John Day, and McNary Dams on the lower Columbia River and at Wanapum Dam in the mid-Columbia River. Spillway flow deflectors have also be installed at Ice Harbor, Lower Monumental, Little Goose, and Lower Granite Dams on the lower Snake River. Flow deflectors at these projects have reduced TDG production at spillways to 120 percent4 or below for discharges up to 7,000 to 10,000 cfs per spill bay (specific discharges of 140 to 200 cfs per ft) depending upon the specific project. Spillway

4 The 120 percent TDG level has been adopted as maximum TDG standard at the fixed monitoring stations for the Snake and Columbia Rivers, when spilling to aid fish migration. Additional TDG criteria must also be met. Waivers from the 110 percent standard have been granted by appropriate state agencies.


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deflectors have not reduced TDG levels to the state standard of 110 percent except during very small specific spillway discharges on the order of 3,000 cfs/bay. For most of the dams where deflectors have been the most effective, the stilling basins are relatively deep (>35 ft). For these stilling basins, a significant reduction in the mean bubble depth is possible. For much shallower stilling basins, obviously, the reduction in TDG levels will be much less dramatic.

The objective of spillway flow deflectors is to redirect the vertical momentum of a spillway jet into a horizontal surface jet. This type of flow tends not to plunge to the bottom of the stilling basin, thus keeping the entrained air exposed to lower hydrostatic pressures and resulting in lower TDG levels. This surface jet remains highly aerated and reduces the mean depth of entrained air during passage through the stilling basin compared to a non-deflected stilling basin release. A strong recirculating flow generally develops beneath the stilling basin water surface that supplies water to the developing surface jet and can be a vehicle for drawing water into the stilling basin. The transport of water into the stilling basin under the spillway surface jet can capture a large portion of powerhouse flows and increase the TDG loading caused by project releases. The entrainment of powerhouse flows into the stilling basin at Little Goose Dam has been shown to effectively double the TDG loading in the Snake River (Schneider and Wilhelms, 1998). The addition of spillway flow deflectors significantly alters the functioning the stilling basin to dissipate the energy contained a spillway discharge. This higher energy is carried out into the tailwater channel where the TDG exchange process continues. If the depth of flow in the tailwater channel becomes shallower than the stilling basin, an additional TDG abatement benefit may occur. However, if the available depth downstream of the stilling basin increases, the potential for larger TDG levels is present. The low rates of TDG exchange at Ice Harbor dam compared to the other Snake River projects is attributed to the delivery of highly aerated flow to a shallow tailwater channel (Wilhelms and Schneider, 1998). The Ice Harbor flow deflectors have reduced TDG levels by as much as 25 percent TDG for spill levels of 6,000 cfs to 8,000 cfs per bay and have increased the 120 percent TDG spill cap from 25,000 cfs to 110,000 cfs as measured at the tailwater fixed monitoring station. Spillway flow deflectors are concrete structures located on the spillway face (Figure 15), generally at an elevation slightly below that of the design tailwater elevation. They usually span the full width of the spill bays and normally extend horizontally 8 to 15 feet out from the spillway face with some type of toe curve transition from the spillway face to the horizontal portion of the deflector. Flow deflectors turn the highly aerated spillway flow to produce a surface-skimming water jet that has a horizontal instead of a vertical orientation. Flow deflector designs are based on the results of physical model studies. Details such as length, elevation, and transition curve radius are fine tuned during this process to produce the desired surface jet trajectory for a wide range of spillway discharges and tailwater stage. Performance is optimized when the elevation of the deflector (associated with a design discharge and tailwater elevation) is set to provide a smooth skimming flow. If the tailwater elevation relative to the deflector is too low, the deflected discharge generates a plunging flow, subjecting aerated flow to higher pressures. If the tailwater elevation is too high, the deflected discharge generates a highly aerated undular flow that may also draw air deep into the stilling basin. During very high


27

flows, the spillway jet overrides the deflector, allowing the stilling basin to operate as designed. The impacts of any spillway or deflector modifications on juvenile and adult fish passage, channel erosion, and the structural integrity of the dam must be considered. Model studies and prototype evaluations have shown deflectors in the outside spillway bays create strong cross-currents (or lateral flows) immediately downstream of the adult fishway entrances. Tailrace conditions altered by modified or additional deflectors may disorient and delay adult fish seeking passage through the fishway entrances adjacent to the spillways. The effect of additional or modified flow deflectors on adult fish passage must be evaluated on a project-by-project basis accounting for differences in project configurations (e.g., relative location of fishway entrances, channel bathymetry, and the existence of guide walls separating the entrances from the stilling basin). However, studies of adult migrant delay conducted to date following installation of deflectors on spillway bays adjacent to fish ladder entrances have not shown any delay in adult migrant passage associated with operation of these newly modified bays. The hydraulic conditions generated by deflected spill flow may directly impact survivability of juvenile salmonids migrating downstream. Turbulence in the vicinity of stilling basin baffle blocks and endsills may be increased with additional or modified flow deflectors. Increased turbulence in the vicinity of these structures may result in increased mechanical injury. Though many of the projects are similar, the influence of spillway modifications on juvenile fish passage must be evaluated on a project-by-project basis. There have been studies of direct mortality of spill-passed juvenile migrants that indicate higher mortality for juvenile fish passed through spillway bays with deflectors. The ability of the spillway and stilling basin to adequately dissipate energy of spillway design flows must not be compromised with any spillway modifications. Model studies show the standard 12.5-foot-long flow deflectors will be overridden by the spillway design flood discharges. When this happens, the hydraulic jump generated by spillway design flood flows is fully contained within the stilling basin. Extending the deflector length may result in insufficient energy dissipation of the project design flows, forcing the hydraulic jump and high-energy flow into the downstream channel, potentially causing erosion of the downstream channel and shoreline. When functioning properly, the spillway flow deflectors create an intense vertical re-circulation cell beneath the deflected jet. Flow from the deflected jet is drawn from the tailrace channel, downstream of the stilling basin’s endsill, back upstream along the floor of the stilling basin to the toe of the spillway. This circulation of flow has the potential to pull rock material from below the endsill into the stilling basin, which can cause erosion of the spillway toe. If left unchecked, this could cause a dam safety problem and, over a period of time, may require costly structural repairs to the spillway’s stilling basin. The addition of spillway flow deflectors at Rocky Reach Dam would require the removal of nappe deflectors and change the energy dissipation function of the stilling basin. The unique design of the stilling basin endsill at Rocky Reach results in a surface jet being introduced into the adjoining tailwater channel. This type of surface jet is similar, in many respects, to flow conditions generated by spillway flow deflectors at other


28

Columbia and Snake river dams. The influence of the upstream baffle and endsill would be different with spillway flow deflectors. The potential to entrain a much larger portion of powerhouse flows would be a likely outcome of the addition of spillway flow deflectors given proximity of powerhouse releases and experience of flow deflectors on the Snake River projects. The associated benefits of spillway flow deflectors at Rocky Reach Dam to abate TDG production is much smaller than other projects with much deeper standard stilling basin designs. The transport of highly aerated flow coupled with higher turbulent velocities to the deeper tailwater channel could further reduce the benefits associated with the addition of spillway flow deflectors. In an effort to quantify how much improvement could be attained through the addition of spillway flow deflectors at Rocky Reach Dam, a comparison with TDG exchange properties at Lower Granite Dam was conducted. Lower Granite Dam is located on the Snake River at RM 107.5. The spillway has eight spill bays with a 50 ft wider, with spillway flow deflectors on each bay at elevation 630. The stilling basin at Lower Granite Dam is of conventional design with a typical depth of flow of 52 ft. In contrast, the stilling basin depth of flow at Rocky Reach dam ranged from about 27 ft to 36.5 ft during the 2002 TDG exchange study. Powerhouse and spillway releases interact strongly at Lower Granite Dam as a large portion of the powerhouse releases are entrained into the aerated flow in the stilling basin. During the 2002 spill season (CEERDC, 2003), the peak TDG saturation in spillway releases reached 115 percent of saturation for a spill discharge of about 32 kcfs, and 120 percent for a spillway discharge of about 53 kcfs. The TDG response at Rocky Reach Dam was similar to conditions observed at Lower Granite Dam with spillway flow deflectors. The TDG saturation as a function of the specific spillway discharge at both Lower Granite and Rocky Reach Dams is shown in Figure 16. The peak TDG response for the standard spill pattern (LWG-Std) and spill pattern with the removable weir crest (LWG-RSW) at Lower Granite Dam both generally fall above the peak TDG response observed at Rocky Reach Dam. The several instances where the Rocky Reach TDG saturation falls above the response at Lower Granite Dam correspond with non-standard spill events where flow was distributed over a portion of the spillway. In general, the TDG response for a specific spillway discharge of 4 kcfs/bay was similar for Rocky Reach and Lower Granite Dams. However, for specific spill discharge greater than 6 kcfs/bay, the TDG response at Rocky Reach Dam was about 2-5% saturation less than the response observed at Lower Granite Dam. The powerhouse entrainment contribution to TDG loading at both projects is another component of the TDG exchange properties at both projects. The added mass relationship reflecting the entrainment of powerhouse flows at Lower Granite Dam was estimated to be 100 percent of the spillway discharge as limited by the powerhouse discharge. This means that for a powerhouse discharge of 70 kcfs and a spillway discharge of 30 kcfs at Lower Granite Dam, about 42% of the powerhouse discharge (30 kcfs) will be entrained into the aerated spillway flow. This effectively doubles the volume of water directly impacted by aerated spillway releases and reduces of availability of powerhouse releases with lower TDG levels to dilute spill TDG pressures. In contrast, at Rocky Reach Dam, the added mass or entrainment discharge of powerhouse releases would be only 12.7 kcfs as determined from Equation 6. Although the addition of spillway flow deflectors has provided significant TDG abatement benefits at many mainstem Columbia and Snake River dams, it appears to have a limited


29

potential TDG benefit at Rocky Reach Dam. The TDG exchange properties at Rocky Reach Dam are comparable with, and in many cases superior to, the TDG exchange attributes observed at Lower Granite Dam, a project with spillway flow deflectors properly functioning on all eight spillbays. The relatively low rates of TDG exchange observed at Rocky Reach Dam can be attributed to the shallow stilling basin, high rate of energy dissipation, relative size of the spillway, and influence of the sloped end sill. It is possible that a spillway flow deflector could increase the TDG exchange properties at Rocky Reach Dam by extending the zone of highly turbulent aerated flow conditions into the deeper tailrace channel below the stilling basin. It is the conclusion from this assessment that the spillway flow deflector alternative for Rocky Reach Dam has a low probability for providing effective TDG management.

Entrainment Cutoff Wall

The orientation of powerhouse and spillway discharges at Rocky Reach Dam have a strong potential to interact quickly within the stilling basin and adjoining tailwater channel. The powerhouse discharge is directed laterally across the channel and into the path of highly aerated spillway releases. A return current into the stilling basin was evident during spillway releases not involving spill bay 2 during the TDG testing conducted in 2002. A depression of the tailwater stage within the stilling basin was noted during these spill events resulting in a strong current being directed into the stilling basin downstream of spill bay 2. The turbulent energy contained in spillway releases has a large potential to entrain nearby water that often originates as powerhouse releases. As previously mentioned, the stilling basin endsill results in a surface jet being introduced into the adjoining tailwater channel. A surface jet can induce an entrainment flow to be drawn beneath the jet from the powerhouse side of the channel. The characterization of flow passing over the endsill and into the tailwater channel was observed during physical model studies of Rocky Reach Dam.

If the interaction of powerhouse and spillway flows occurs in highly aerated and turbulent flow, the resultant TDG loading can be increased significantly. In this case, the component of powerhouse flow entrained into aerated spillway flows will be exposed to the exchange of atmospheric gasses resulting in TDG supersaturation. The amount of powerhouse water that typically contains lower TDG pressures than spillway releases, available to dilute spillway releases, will also be lessened in this case. A wall constructed between the powerhouse and spillway can prevent a substantial portion of powerhouse flows from becoming entrained and aerated within the spillway’s stilling basin and tailwater channel. The resulting partitioning of project flows will also provide a larger volume of powerhouse discharges at a lower TDG level to dilute the high TDG pressures generated during spillway operations within the developing mixing zone. This alternative does not reduce the level to which the spill flows become saturated with dissolved gasses but reduces the total volume of flow exposed to aeration and elevation of TDG pressure. In this way, it reduces the total mass of TDG produced by spill.


30

The importance of the entrainment of powerhouse releases on the resultant TDG loading has been well documented for projects on the Snake River in both field studies of TDG exchange and in general physical hydraulic models. Near-field tests at Little Goose and Ice Harbor indicate as much as 100 percent of the powerhouse flow can be drawn into the stilling basin under certain operating conditions. The fate of powerhouse flows entrained into the stilling basin was explored during the Little Goose TDG exchange field study conducted in February 1998 (Schneider and Wilhelms, 1998). Spillway flow deflectors are installed on six of the eight spillbays at Little Goose Dam. The cross sectional average TDG saturation in the Snake River at the near the tailwater FMS below Little Goose was observed to be about 125.8 percent during a 60,000 cfs spillway release (using an adult passage spill pattern) with no powerhouse flow (100 percent spill). The test was repeated by adding a 60,000 cfs powerhouse discharge with a background TDG saturation of 101 percent along with the 60,000 cfs spillway release (using an adult passage spill pattern) (50 percent spill). The 50 percent spill event resulted in a cross sectional average TDG saturation of 125.4 percent or about the same conditions that were generated during the 100 percent spill event. The observations from this study support the conclusion that powerhouse flows entrained into the stilling basin can experience the same degree of TDG exchange as water passing over the spillway.

Both the Lower Granite and Ice Harbor general physical models were used to establish the entrainment cutoff wall length necessary to prevent the entrainment of powerhouse flow into the spillway stilling basins. Observations of dye released in the models indicate a wall length of approximately 150 feet extending downstream from the existing powerhouse prevented powerhouse flows from becoming entrained within the spillways stilling basin over the entire normal operating range. The height of the wall would vary between projects and would range from a low of approximately 40 feet at Ice Harbor to a high of 90 feet at Little Goose. The differential head across the wall was estimated to range from 2 to 3 feet depending on project operations. However, it may be possible to construct an effective wall that would remain submerged, thereby reducing or eliminating any differential head. The orientation, length, and height of an entrainment cutoff wall at Rocky Reach would likely require a project-specific model study. Tailrace conditions must also be evaluated for adult and juvenile fish passage and channel erosion concerns. The general location and orientation of an entrainment cutoff wall at Rocky Reach Dam is shown in Figure 17.

The TDG abatement benefits of an entrainment cutoff wall are best quantified by changes to the TDG loading associated with the entrainment of powerhouse releases into aerated spillway flows at Rocky Reach Dam. The project TDG loading is dependent upon both powerhouse and spillway discharges and the background TDG saturation in the Columbia River upstream of the dam. The entrainment cutoff wall will provide the greatest degree of improvement when there is a large entrainment of powerhouse flow into the aerated spillway discharge and the ambient background TDG pressures are low.

The estimation of TDG exchange for Rocky Reach Dam presented in this study can be used to estimate the reduction in TDG loading provided by a properly designed entrainment cutoff wall. The equations 2 and 6 can be used to estimate the peak and


31

cross sectional average TDG saturation as a function of the background TDG saturation, powerhouse and spillway discharge, and spill pattern. If an entrainment cutoff wall can be designed to eliminate 100 percent of the entrainment flow, the corresponding peak and cross sectional average TDG saturation can be determined from this set of equations. The peak TDG saturation in the spillway discharge was assumed to be independent of the flow partitioning caused by the entrainment cutoff wall. A series of scenarios were used to estimate the TDG abatement benefits associated with an properly designed entrainment cutoff wall capable of eliminating 100% of powerhouse entrainment into aerated spillway flow. The background TDG levels were assumed to range from 105, 110, 115, 120, and 125 percent for total river flows of 150, 200, and 250 kcfs. The powerhouse capacity based on the availability of 10 and 11 turbines was 200 kcfs and 220 kcfs, respectively. Five alternative operational policies requiring spilling 0, 5, 10, 15, 25, and 35 percent of total river flow up to the available powerhouse capacity was used to determine the powerhouse and spillway discharge. The resulting TDG saturation below Rocky Reach Dam for existing and entrainment cutoff wall conditions are shown in Table A1.

A subset of TDG estimates are listed in Table 3 for background TDG saturation of 110 percent, powerhouse capacity of 200 kcfs, operational policy of 25% spill, during total river flows of 150, 200, and 250 kcfs, for both base and entrainment cutoff wall conditions. The base condition during a total river flow of 150 kcfs, operational policy of 25% spill or 37.5 kcfs, generates a peak TDG saturation of 116.6% and an average cross-sectional TDG saturation of 112.6% (Case 154). The entrainment cutoff wall alternative for the same set of conditions will generate the same peak TDG saturation of 116.6% but a smaller average cross-sectional TDG saturation of 111.6% due to the elimination of the entrainment of powerhouse flow. The amount of TDG enhancement afforded by the entrainment cutoff wall increases with higher river flows. At a total river flow of 150 kcfs the entrainment cutoff wall reduces the average TDG saturation by about 1.0 percent (112.6-111.6). The reduction in average TDG saturation resulting from the EC wall for total river flows of 200 and 250 kcfs were 1.3 and 1.6 percent, respectively.

1 Base-Structural configuration as of 2004, Entrainment Cutoff Wall- EC Wall. 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern

Table 3 Total Dissolved Gas Saturation estimate as a function of structural alternative, spill policy, river flow, and background TDG saturation for Rocky

Reach Dam

Case Structure Alternative1

Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs)

Qtotal4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 154 Base 0.25 200 150 112.5 37.5 22.7 110 116.6 112.6 2.6 155 Base 0.25 200 200 150.0 50.0 32.0 110 118.3 113.4 3.4 156 Base 0.25 200 250 187.5 62.5 41.4 110 120.0 114.1 4.1 334 EC Wall 0.25 200 150 112.5 37.5 0.0 110 116.6 111.6 1.6 335 EC Wall 0.25 200 200 150.0 50.0 0.0 110 118.3 112.1 2.1 336 EC Wall 0.25 200 250 187.5 62.5 0.0 110 120.0 112.5 2.5


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7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

The TDG impacts associated with a range of forebay TDG levels for a total river flow of 150 kcfs and an operational policy of 25% spill is listed in Table 4. The EC wall causes a net reduction in the average TDG saturation in the Columbia River as long as the forebay TDG saturation is less than the estimated TDG saturation in spillway releases. However, when the forebay TDG saturation is larger than the estimated TDG saturation in spill, a net reduction in the average TDG saturation is generated and the entrainment cutoff wall reduces the magnitude of the improvement. For instance, if the forebay TDG saturation is 120%, the resultant average TDG saturation for the base condition is estimated to be 118.6 (case 160) compared to 119.1 percent (case 340) for the EC wall alternative. In this case, the entrainment of powerhouse flows with a high initial TDG saturation is beneficial since the spillway produces TDG saturations of only 116.6 percent. There are many examples of spillway operations at The Dalles, Bonneville, and Ice Harbor Dams resulting in a net reduction in the TDG loading of the Columbia and Snake Rivers in support of the net degassing estimates shown in Table 4.

Table 4 Total Dissolved Gas Saturation estimate as a function of structural

alternative, spill policy, river flow, and background TDG saturation for Rocky Reach Dam


Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs)

Qtotal4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 151 Base 0.25 200 150 112.5 37.5 22.7 105 116.6 109.6 4.6 154 Base 0.25 200 150 112.5 37.5 22.7 110 116.6 112.6 2.6 157 Base 0.25 200 150 112.5 37.5 22.7 115 116.6 115.6 0.6 160 Base 0.25 200 150 112.5 37.5 22.7 120 116.6 118.6 -1.4 163 Base 0.25 200 150 112.5 37.5 22.7 125 116.6 121.6 -3.4 331 EC Wall 0.25 200 150 112.5 37.5 0.0 105 116.6 107.9 2.9 334 EC Wall 0.25 200 150 112.5 37.5 0.0 110 116.6 111.6 1.6 337 EC Wall 0.25 200 150 112.5 37.5 0.0 115 116.6 115.4 0.4 340 EC Wall 0.25 200 150 112.5 37.5 0.0 120 116.6 119.1 -0.9 343 EC Wall 0.25 200 150 112.5 37.5 0.0 125 116.6 122.9 -2.1

1 Base-Structural configuration as of 2004, Entrainment Cutoff Wall- EC Wall. 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

The entrainment wall will prevent powerhouse flows from being exposed to

aerated conditions in the stilling basin. In addition, powerhouse releases will retain the TDG levels transported to the projects from upstream allowing the dilution of


33

spillway releases in the developing mixing zone downstream of the highly aerated flow conditions. The mixing of powerhouse discharges into spillway flows downstream of the entrainment cutoff wall is anticipated with this design. The benefits of this alternative are derived by not gassing up powerhouse releases when forebay TDG levels are less than the TDG saturation generated in spillway flows. If the entrainment of powerhouse flows is small or background TDG levels high, the benefits of partitioning project flows with an entrainment cutoff wall will be small or negative. This alternative will not improve the TDG performance of an existing spillway. That is to say that the effectiveness of this alternative will not be readily observed at a single sampling station located directly below the stilling basin such as at station FOP1 but will be apparent in observations effectively sampling the cross sectional average TDG levels. The reduction in the TDG loading would be evident at mixed river sampling station such as in the forebay at Rocky Island Dam. However, preventing entrainment of powerhouse flow will limit the total volume of flow being supersaturated with dissolved gasses and should result in lower observed pressures in the receiving pool following complete mixing. The entrainment cutoff wall will allow the mixing and dilution of powerhouse flows with spillway flows to occur further downstream where there is little or no exposure to heavily aerated flow and high hydrostatic pressures.

Determination of the detailed performance of an entrainment cutoff wall would

require further study. The potential impact of the entrainment cutoff wall on limiting laterally entrained flows will influence circulation patterns and energy dissipation of project releases and impact the development of the mixing zone. The amount of powerhouse water entrained into aerated spillway flows can be more accurately determined through controlled field testing where a fixed spill discharge is sampled during operating scenarios of 100, 80, 60, 40, and 20 percent spill events. The entrainment cutoff wall is likely to result in a reduction in total head at the north end of the powerhouse. The degree of increasing the tailwater stage will depend upon the design elements of the wall (orientation, height and length) as well of the powerhouse release and distribution between units. Further field studies and/or model investigations may be needed to further define the hydraulic and environmental flow conditions caused by the partitioning of releases by an entrainment cutoff wall below Rocky Reach Dam.

The separation wall would prevent any juvenile salmonids that are passing through the powerhouse from becoming entrained within the turbulent and high TDG environment in the stilling basin. The separation wall would need to be properly designed and constructed with adequate consideration for guidance of adult salmonids and steelhead.

Raised Stilling Basin Floor The concept of a raised stilling basin was evaluated for application to lower Snake River projects (CENWP-NWW 1996). Raising the stilling basin apron reduces the depth to


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which aerated spillway flow can plunge, thereby reducing the hydrostatic pressures that the air bubbles experience. As a consequence, TDG concentrations in the stilling basin are reduced. The importance of the aerated depth of flow in the stilling basin was documented in two investigations of TDG exchange at The Dalles Dam on the Columbia River and at Ice Harbor Dam located on the Snake River. The Dalles Dam is located at river mile 191.5 on the Columbia River and creates a water surface differential from upstream to downstream of 78 ft. The spillway at The Dalles has a total width of 1370 feet and consists of 23 tainter gate-controlled bays each with a width of 50 ft. There are no spillway deflectors at The Dalles Dam. The horizontal apron-type stilling basin at The Dalles is about 190 ft. long with an invert elevation of 55 ft yielding a typical depth of flow of 25 ft. One row of baffle blocks 8 ft. high and an end sill 12 ft. high provide for energy dissipation in the stilling basin. Three training wall extending perpendicular to the spillway separate the stilling basin into four sectors. The tailwater channel downstream of the stilling basin has a mean elevation of 68 ft. A detailed TDG exchange study was conducted at The Dalles Dam during 1996 where the TDG pressures were measured just downstream of the stilling basin endsill. TDG saturation at The Dalles stilling basin end sill, did not exceed 140 percent saturation during spill events with discharges as high as 15,000 cfs per bay (300 cfs per ft of spillway width) (Schneider and Wilhelms, 1996b) and average conditions ranged from 125-135 percent. The TDG exchange continued downstream of the stilling basin below The Dalles Dam with a net degassing taking place throughout the shallow tailrace channel resulting in final TDG levels ranging from 120-125 percent. Ice Harbor Dam is located at river mile 9.7 on the Snake River and creates a water surface differential from upstream to downstream of about 94 ft. The spillway at Ice Harbor Dam has a total width of 590 feet and consists of 10 gate-controlled bays each with a width of 50 ft. The horizontal apron-type stilling basin at Ice Harbor Dam is about 210 ft. long with an invert elevation of 304 ft. With normal tailwater at el 344, the normal depth in the stilling basin was about 40 ft or nearly twice the stilling basin depth at The Dalles Dam. One row of 8-ft-high baffle blocks and a 12-ft end sill provide energy dissipation in the stilling basin. Type II spillway deflectors, which are 12.5 ft long horizontally with a 15-ft radius toe curve, were installed at Ice Harbor Dam during the years of 1997-1999 . A splitter wall separates end bays 1 and 10 from the interior spillbays. The tailwater channel downstream of the stilling basin is generally above elevation 320 ft with the exception of a large depression located upstream of the end of the lock guide wall. Prior to the installation of spillway flow deflectors, a TDG exchange investigation was conducted at Ice Harbor Dam in 1996. The TDG levels monitored at the end sill of the Ice Harbor stilling basin prior to flow deflector installation reached as high 167 percent saturation during a spill discharge of 6,000 cfs per spill bay (120 cfs per ft of spillway width) (Schneider and Wilhelms, 1997). The TDG saturation at the Ice Harbor end sill ranged on average from 125 to 165% as a function of the spillway specific discharge


35

which ranged from 2 to 6 kcfs/bay during the study period. The resultant TDG saturation at the end of the aerated zone ranged from 118 to 134 percent which suggests a region of degassing is present downstream of the stilling basin. The TDG saturation exiting the stilling basin at Ice Harbor Dam was nearly double the levels observed at The Dalles Dam which was also consistent with the difference in the stilling basin depths between the two projects. The Rocky Reach stilling basin apron elevation varies from about 582 to 590 resulting in stilling basin maximum depths ranging from 30 to 38 feet when tailwater is at el 620. However, the continuous impact sill and end sill significantly reduce the average depth of the stilling basin. By including the impact and end sills, the average elevation of the stilling basin is approximately 596 (Schneider, 2003). As a consequence, the average stilling basin depth typically ranges from 20 to 25 ft and is similar to the stilling basin depths typically experienced at The Dalles Dam. Thus, the TDG exiting the stilling basin should be about the same as The Dalles. This however, does not include the effects of the large nappe deflectors on the Rocky Reach Spillway or the effects of the continuous impact sill. The effect of the plunging action of the spillway nappe off of these large deflectors is unknown and no other spillways of similar design have been encountered. The same is true for the upwelling effects of the continuous impact sill. Furthermore, the degassing that normally occurs in the tailrace just downstream of the stilling basin is not included. The variation in elevation of the stilling basin floor at Rocky Reach Dam provides an opportunity to evaluate the influence of stilling basin depth on TDG exchange and hence the potential TDG benefits associated with raising the stilling basin floor. The stilling basin floor associated with spill bays 9-12 at Rocky Reach dam at elevation 590 are about 5 feet higher than the stilling basin floor associated with bays 2-5 as shown in Figure 4. The maximum TDG saturation observed below the spillway at station FOP1 for uniform spill over bays 2-5 were consistently lower than conditions observed during uniform spill over bays 9-12 as shown in Figure 11. In general, the TDG saturation during spill over bays 9-12 were from 1 to 2 percent higher than comparable spill over bays 2-5 even though the stilling basin average depth of flow was less during the uniform spill over bays 9-12. These observations suggest that simply raising the stilling basin floor may not have the intended effect of reducing the TDG saturation of spillway flows. The circulation pattern and air entrainment influenced by the nappe deflectors, impact baffles, and sloped end sill override the importance of the elevation of the stilling basin floor at Rocky Reach Dam. The stilling basin as currently configured at Rocky Reach Dam has a depth comparable to those experienced at The Dalles Dam. However, the resultant TDG exchange at The Dalles Dam was considerable higher than conditions observed at Rocky Reach Dam. The TDG saturation in spillway flows as a function of stilling basin depth at The Dalles Dam and Rocky Reach Dam are shown in Figure 18. The trend line of TDG saturation as a function of stilling basin depth at Rocky Reach Dam was generally about 7 percent


36

saturation less than a similar trend line through the data observed at The Dalles Dam. In both cases, shallower flow conditions lead to smaller TDG conditions. The alternative of raising the elevation of the stilling basin at Rocky Reach Dam is likely to have a relatively small impact on the TDG exchange properties during spillway operations based on TDG exchange observations at Rocky Reach Dam as compared to similar observations at The Dalles Dam. Further consideration of this alternative is not recommended as an effective TDG management alternative at Rocky Reach Dam. Further consideration of this alternative would require a physical model study to assess the hydraulic performance of a modified stilling basin for a range of discharges and tailwater elevations up to the maximum probable flood flow. Raised Tailrace Channel A rapid and substantial desorption of supersaturated dissolved gas takes place in the tailwater channel immediately downstream of the stilling basin. As the entrained air bubbles are transported downstream, they rise above the compensation depth in the tailwater channel. While above the compensation depth, the air bubbles strip dissolved gas from the water column. Field studies have shown that gas absorption occurs in the stilling basin and significant degassing occurs in the first 200-300 ft downstream of the stilling basin. The TDG data collected at The Dalles stilling basin showed a consistent reduction in TDG pressures during passage of aerated flow in the tailrace channel on the order of 40 percent of the delta pressure, or pressure above the local atmospheric pressure, observed exiting the stilling basin. These studies and historical data suggest that tailrace depth has a direct bearing on the TDG level produced by a project. Thus, one alternative to reduce TDG levels is to elevate the tailrace channel, thereby reducing the depth of flow associated with the aerated flow exiting the stilling basin by promoting the striping of TDG gasses. The depth of tailrace channel flow at The Dalles Dam has been found to be the primary determinant of TDG exchange during spillway releases. The tailwater depth was found to be linearly related to the exchange of TDG during spill at the Dalles Dam during the 2000 spill season. An increase in tailwater depth of flow by 1 foot resulted in an increase in the TDG pressure of about 8 mm Hg (or about 1 % saturation). Conversely, a reduction in tailwater depth of flow by 1 foot resulted in a reduction in the TDG pressure in spill flow by 8 mm Hg. The tailwater stage is a function of total river flow. Therefore, the powerhouse release has a direct influence on the magnitude of TDG pressure generated in spill at The Dalles Dam. An increase in powerhouse load will result in an increase in tailwater stage causing a higher TDG pressure in spill. However, the average TDG levels in the Columbia River will be reduced below The Dalles Dam for this operation change when forebay TDG levels are below 120%. The TDG exchange in spill at The Dalles Dam was consistently higher than observed at Rocky Reach Dam even though the tailwater channel depth of flow at The Dalles Dam was less than half that at Rocky Reach Dam. The TDG saturation in spill at The Dalles Dam using the juvenile spill pattern during 2000 as a function of tailwater channel


37

elevation is shown in Figure 19 with corresponding data at Rocky Reach Dam during spill using the standard spill pattern. The tailwater depth of flow at Rocky Reach Dam was calculated by assuming and average tailwater channel elevation of 585 ft (Figure 4). A direct linear relationship between the TDG saturation in spill and tailwater channel depth of flow is indicated at The Dalles Dam. The relationship between tailwater channel depth of flow and TDG production at Rocky Reach Dam is weak, although the slope of the relationship is similar to that observed at The Dalles Dam. Several predictive models were developed during the DGAS program (Schneider and Wilhelms, 1998) to estimate the effects of a raised tailrace channel on TDG exchange at Columbia and Snake River projects. The TDG estimates were based on the application of theoretical and conceptual models of the gas exchange processes, an analysis of historical data, application of an empirical relationship based on near-field measurements, and an analysis of degassing in the tailrace region. These descriptions of TDG exchange incorporated terms to reflect the changes in gas transfer associated with raising the tailwater channel and reducing tailwater depth. Water quality, project operations, and flow data from the historical data base and field studies at Ice Harbor and The Dalles Dam were used to quantify the current TDG exchange properties and characterize the effects of tailwater depth. These models are not applicable to conditions at Rocky Reach Dam due to insufficient TDG information within the aerated flow field and the impact of the sloped and slotted end sill. The TDG levels exiting the stilling basin were used to develop a TDG exchange model of the tailrace at The Dalles and Ice Harbor Dams. First order exchange coefficients were developed from field data and applied to the passage of aerated flow through the tailwater channel. The initial TDG pressures exiting the stilling basin for a range of flow conditions were used as boundary conditions in the application of this model. This boundary condition information is not available at Rocky Reach Dam. In addition, the sloped and slotted end sill forces water exiting the stilling basin at Rocky Reach Dam to elevations above 615 ft at non-slotted sections and to elevation 607 ft at slotted sections. The end sill forces the highly aerated stilling basin flow to a depth of 5 ft for the non-slotted sections and less than 13 ft for the slotted section for a typically river flow of 150 kcfs. The tailwater stage as a function of total river flow is shown in Figure 20 for Rocky Reach Dam. A surface oriented jet is formed by the slopped transition from the stilling basin floor to the end sill (Figure 3). The resultant hydraulic conditions that develop in the tailrace channel at Rocky Reach Dam are similar to conditions that develop as a result of spillway flow deflectors at main stem projects like John Day, McNary, and Bonneville Dams. The central difference between these two types of structures is that the initial plunge is not avoided at Rocky Reach Dam. However, the continuous baffle and end sill result in a more surface oriented flow that prevents entrained bubbles from being exposed to high total pressures and promotes the stripping of TDG pressures. Raising the tailrace channel bottom at Rocky Reach Dam is likely to be an ineffective measure of TDG management because most of the TDG exchange occurs in the surface oriented jet exiting the stilling basin and is not bound by plunging flows limited by the tailwater channel depth of flow. This is the same


38

reason why combining spillway flow deflectors with a raised stilling basin is not an effective TDG management combination. Adopting this alternative would also require a physical model study to assess the hydraulic performance of the tailrace for a range of discharges and tailwater elevations up to the maximum probable flood flow. Since the tailrace fill material would require protection from scour, riprap or other protection would have to be considered. Raised Stilling Basin with Deflectors The concept of raised tailrace topography was also evaluated for application to lower Snake River projects (CENWP-NWW 1996) with particular emphasis on the Ice Harbor Dam (Schneider and Wilhelms, 1998). For this alternative, the elevation of the channel bed would be increased for a distance from 250 to 500 feet downstream of the stilling basin by about 7 feet. This elevation change would cause a deduction in the depth of flow over this raised channel section by about 40 percent and provide a typical depth of flow of 10 feet. It would not prevent the absorption of dissolved gases in the stilling basin, but would aid in the de-gassing of the spillway or sluiceway flow in the tailrace. This alternative is effective as long as entrained air bubbles are still in solution, but above the compensation5 depth. Thus, in general, this alternative is effective for only a short distance downstream of the stilling basin. The alternative of a raised stilling basin with spillway flow deflectors is a combination of alternative that individually were identified to have limited application at Rocky Reach Dam to manage TDG saturation in spillway flows. The addition of spillway flow deflectors that create a surface jet would negate the effects of raising the stilling basin floor by preventing the transport of entrained air to depth. The effectiveness of a raised stilling basin floor would become influential when spill discharges begin to override the flow deflector, creating a plunging aerated jet. Typically, flow deflectors become ineffective only at very large specific discharges well outside of the design spill discharge range targeted at Rocky Reach Dam to manage TDG exchange up to the 7Q10 event. As a consequence of these factors, the raised stilling basin with spillway flow deflectors is identified as having very limited potential to effectively manage TDG exchange at Rocky Reach Dam. Raised Tailrace with Deflectors The gas transfer associated with spillway releases typically consists of the absorption TDG pressure in the stilling basin followed by a loss of TDG pressure in the tailrace channel. The combination of spillway flow deflectors to minimize the initial plunge of entrained air in the stilling basin and a raised tailrace channel that promotes the stripping of TDG pressures has proven to be an effective TDG management feature.

5 Compensation depth is the depth where the ambient TDG concentration is at equilibrium. Example: For TDG at 110 percent, the compensation depth is about 3.4 ft. Bubbles above the compensation depth will absorb/strip dissolved gas from the water.


39

The combination of spillway flow deflectors with a shallow tailrace channel exists at Ice Harbor Dam located on the Snake River. Ice Harbor Dam spillway currently has spillway flow deflectors on all 10 spill bays and a shallow tailrace channel. The typical depth of flow in the tailrace channel ranges from 11 to 22 ft. The total dissolved gas exchange at Ice Harbor Dam has been found to be a function of both the tailwater elevation and specific spillway discharge. An evaluation of TDG saturation observed at the tailwater fixed monitoring station involving 1336 hourly observations during the 2004 season resulted in the following functional relationship between the delta TDG pressure ? P (TDG pressure minus atmospheric pressure mm Hg), tailwater depth Dtw (tailwater elevation minus channel elevation, ft), and specific spillway discharge qs (kcfs/bay).

)7(47.6958.0 952.0937.0 +=∆ stw qDP The predictive error of this relationship was 3.9 mm Hg for tailwater elevation depths ranging from 12.7 to 22.1 ft and specific spillway discharges ranging from 2.91 to 11.8 kcfs/bay. This relationship quantifies the dependence of TDG exchange on the depth of flow in the tailwater and the specific spillway discharge. The TDG response in spill at Ice Harbor Dam during the 2004 season as a function of tailwater channel depth is shown in Figure 19. The two distinct trends in the TDG response correspond with the application of a bulk (operation of 5 or fewer spill bays corresponds with the higher TDG grouping) versus uniform (operation of 10 spill bays corresponds with the lower TDG grouping) spill pattern. The spill discharge at Ice Harbor Dam as limited by the 120% TDG waiver can be as high as 10 kcfs/bay (100 kcfs total spill) provided shallow tailwater conditions are provided. The TDG saturation in spill at Rocky Reach Dam tended to be slightly greater than conditions observed at Ice Harbor Dam for similar specific spillway discharges. The TDG saturation in spillway release as a function of the specific spillway discharge at Ice Harbor and Rocky Reach Dams are shown in Figure 21. Although the relationship between TDG saturation and specific discharge at Rocky Reach Dam is weak, the tendency for higher TDG pressure in spill at Rocky Reach Dam is evident in this comparison. The TDG response at Rocky Reach Dam is similar to the application of the bulk spill pattern at Ice Harbor Dam for intermediate flows with specific discharges ranging from 5 to 6 kcfs/bay. An investigation was conducted to further raise the elevation of the tailrace channel at Ice Harbor Dam about 7 ft to an elevation of 324 ft. This channel feature would have forced the depth of flow to range from 8 to 15 ft for a distance of 250 ft downstream from the stilling basin end sill. The projected benefits or reduction in TDG saturation in spill at Ice Harbor Dam for raising the tailrace channel by 7 ft estimated to range from less than 1 percent saturation for spill up to 20 kcfs to 3.5% for a spill of 100 kcfs. The construction of spillway flow deflectors with a raised tailrace channel at Rocky Reach Dam that may result in an improvement in TDG management of the Columbia River. The ability to implement this alternative would require a substantial modification


40

to the stilling basin and tailrace channel at Rocky Reach Dam. Nappe deflector removal would be required to properly site the submerged spillway flow deflectors. This alteration would greatly reduce the energy dissipation properties of the stilling basin. It is likely that the tailrace channel would need to be armored to with stand the large hydraulic forces associated with spill delivered downstream of the stilling basin with spillway flow deflectors in place. The tailrace channel would have to be raised to elevation 608 to achieve the depths and TDG exchange performance demonstrated at Ice Harbor Dam. The raised channel would extend about 300 feet below the stilling basin at Rocky Reach Dam as shown in Figure 23. The raised channel is located downstream of spill bays 2-12 and could be extended across the entire spillway to accommodate a change in the standard spill pattern involving spill bay 1. Estimates of TDG exchange at Rocky Reach Dam with spillway flow deflectors and a raised tailrace channel were conducted for a range of total river flow, forebay TDG levels, powerhouse capacity, and spill policies. The TDG exchange relationship developed for Ice harbor Dam in Equation 7 was used to estimate the TDG saturation in spillway flows. The depth of flow was determined from the calculation of the tailwater surface elevation listed in Figure 20 and the elevation of the raised tailrace channel. The raised tailwater channel was assumed to be constructed to an elevation of 608 ft, and have a length of 300 ft downstream of the stilling basin. The specific discharge was calculated by assuming the spill discharge was uniformly distributed over bays 2-11 with a 4 kcfs/bay minimum as currently constrained. The entrainment discharge formulation was unchanged from the base condition and an average atmospheric pressure of 748 mm Hg was used to calculate the TDG saturation. The complete set of TDG estimates can be found in the Appendix A in Table A1 under the structural alternative label of SP&RTW (spillway deflectors with a raised tailwater channel). A TDG estimates for the Base structure alternative and for the spillway deflectors with a raised tailrace channel are listed in Table 5 for a background TDG saturation of 110 percent, powerhouse capacity of 200 kcfs, operational policy of 25% spill, during total river flows of 150, 200, and 250 kcfs. The base condition during a total river flow of 150 kcfs, operational policy of 25% spill or 37.5 kcfs, generates a peak TDG saturation of 116.6% and an average cross-sectional TDG saturation of 112.6% (Case 154). The SP&RTW alternative for the same set of conditions generated a TDG saturation of 112.4 % with an average cross-sectional TDG saturation of 111.0%. The amount of TDG enhancement afforded by the SP&RTW was largest for the total river flow of 200 kcfs were the average TDG saturation was 111.5% compared to 113.4% for the base case. The reduction in average TDG saturation resulting from the SD&RTW for total river flows of 200 and 250 kcfs were 1.9 and 1.6 percent, respectively.


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Table 5 Total Dissolved Gas Saturation estimate as a function of structural alternative, spill policy, river flow, and background TDG saturation for Rocky

Reach Dam


Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs)

Qtotal4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 154 Base 0.25 200 150 112.5 37.5 22.7 110 116.6 112.6 2.6 155 Base 0.25 200 200 150.0 50.0 32.0 110 118.3 113.4 3.4 156 Base 0.25 200 250 187.5 62.5 41.4 110 120.0 114.1 4.1 514 SD&RTW 0.25 200 150 112.5 37.5 22.7 110 112.4 111.0 1.0 515 SD&RTW 0.25 200 200 150.0 50.0 32.0 110 113.7 111.5 1.5 516 SD&RTW 0.25 200 250 187.5 62.5 41.4 110 116.0 112.5 2.5

1 Base-Structural configuration as of 2004, Entrainment Cutoff Wall- EC Wall, spillway deflectors with raised tailwater channel (SD&RTW). 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

The TDG impacts associated with a range of forebay TDG levels for a total river flow of 150 kcfs and an operational policy of 25% spill is listed in Table 6 for the Base and SP&RTW structural alternatives. The SP&RTW causes a net reduction in the average TDG saturation in the Columbia River of about 1.6% saturation. This net improvement over base conditions reduces the increase in TDG levels above forebay conditions when the upstream levels are at 105 and 110 percent but causes an overall reduction in TDG levels when forebay TDG conditions are at and above 115%. The maximum TDG level in spill was reduced from 116.6 % for the base conditions to 112.4% for the SP&RTW structural alternative. There remains considerable uncertainty in the estimates of TDG exchange associated with this alternative as applied to Rocky Reach Dam. The fate of powerhouse flow on the TDG loading at Rocky Reach will likely change with the extensive modification of the spillway and stilling basin required by this alternative. As noted in an earlier section of this report, the entrainment demand a turbulent jet generated by spillway flow deflectors is considerable. The interaction of both the continuous baffles and the stilling basin end sill will interfere with the deflected surface jet and may alter the trajectory and TDG exchange properties of this alternative. Extensive hydraulic model studies will be required to develop a design that provides safe stilling action of spill, accommodates the guidance of adult and juvenile salmonids, and effective TDG management.


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Table 6 Total Dissolved Gas Saturation estimate as a function of structural alternative, spill policy, river flow, and background TDG saturation for

Rocky Reach Dam


Spill Policy2

(Qsp/Qtotal)

Qph-

max3

(kcfs)

Qtotal4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%)

TDG-change11

(%) 151 Base 0.25 200 150 112.5 37.5 22.7 105 116.6 109.6 4.6 154 Base 0.25 200 150 112.5 37.5 22.7 110 116.6 112.6 2.6 157 Base 0.25 200 150 112.5 37.5 22.7 115 116.6 115.6 0.6 160 Base 0.25 200 150 112.5 37.5 22.7 120 116.6 118.6 -1.4 163 Base 0.25 200 150 112.5 37.5 22.7 125 116.6 121.6 -3.4 511 SD&RTW 0.25 200 150 112.5 37.5 22.7 105 112.4 108.0 3.0 514 SD&RTW 0.25 200 150 112.5 37.5 22.7 110 112.4 111.0 1.0 517 SD&RTW 0.25 200 150 112.5 37.5 22.7 115 112.4 114.0 -1.0 520 SD&RTW 0.25 200 150 112.5 37.5 22.7 120 112.4 117.0 -3.0 523 SD&RTW 0.25 200 150 112.5 37.5 22.7 125 112.4 119.9 -5.1

1 Base-Structural configuration as of 2004, Entrainment Cutoff Wall- EC Wall, spillway deflectors with raised tailwater channel (SD&RTW). 2 Spill policy fraction of river spilled subject to powerhouse capacity 3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

Remove Nappe Deflectors The alternative of removing the nappe deflectors as a means of TDG management at Rocky Reach Dam was based on the concept of reducing the amount of air entrained into the spillway release. Although it is likely that a fully aerated nappe has the potential to entrain higher rates of air at the plunge point compared to a spill bound by the spillway channel, it is uncertain whether this higher air to water ratio results in an increase in the net mass transfer. If the amount of air entrained into the spill is a limiting component to mass transfer, then the additional surface area of entrained bubbles will add to the rate of mass transfer. However, there is considerable evidence to support the conclusion that the amount of entrained air is not a limiting component to the net mass transfer of atmospheric gasses in standard spill events at main-stem dams on the Snake and Columbia Rivers. The hypothesis that the volume of entrained air is not a limiting component to mass transfer is support by two properties consistently observed at many dams in the Columbia River basin: 1. The resultant TDG pressure in spill flow is independent of the initial TDG pressure in the forebay and 2. The entrainment of


43

powerhouse flow into aerated spill does not reduce the resultant TDG pressure in this combined discharge. One common feature of TDG exchange at nearly all mainstem dams on the Columbia river is that the a specific spill magnitude, spill pattern, and tailwater stage will result a consistent TDG pressure regardless of the initial TDG pressure in the forebay. This condition is possible because the rate of TDG exchange in the stilling basin and adjoining tailwater channel is dominated by the pressure time history of entrained air. The equilibrium established in the zone of highly aerated flow below the spillway is attained regardless of the initial TDG pressure because of the abundance of entrained air, elevated pressures governing the local saturation concentration, and high rate of turbulence exchange. The depth of flow is often the limiting factor on the TDG exchange in spillway flows where an upper TDG threshold is reached. This condition was observed at Chief Joseph Dam where spillway flows with a specific spill discharge of 5 kcfs/bay and greater resulted in the same resultant TDG saturation in spillway flows (Schneider and Carroll, 1998). The fate of powerhouse flow entrained into the aerated flow conditions in the stilling basin is another observation supporting the hypothesis that entrained air is not a limiting component to TDG transfer in typical spillway releases. The entrainment and subsequent TDG uptake in powerhouse flows at Little Goose Dam to levels comparable to undiluted spillway flow suggest that sufficient surface area was available to treat both spill and powerhouse flows. In situations where the powerhouse flow far exceeds the entrainment demanded by spill, a mixing zone will develop where the redistribution of TDG pressures in spill and powerhouse flow is a prominent process. The spillway bay 1 at Rocky Reach Dam does not contain a nappe deflector and could be used to test the TDG properties of this structural configuration. However, The Dalles dam has a standard ogee spillway with a stilling basin depth similar to Rocky Reach Dam. The resultant TDG exchange at The Dalles Dam was considerable higher than observed at Rocky Reach Dam over the full range of operations as shown in Figure 18. The peak TDG saturation in spillway flow was anywhere from 2 to 10 percent saturation less at Rocky Reach Dam when compared to a similar specific spillway discharge at The Dalles Dam. The hydraulic action caused by the upstream baffle and end sill at Rocky Reach Dam are probably responsible to the different TDG exchange attributes between these projects.

Conclusions and Recommendations A detailed technical assessment of the total dissolved gas exchange characteristics of Rocky Reach Dam has been conducted for current conditions and nine different operational and structural TDG management alternatives. This analysis was based on direct observations of TDG exchange at Rocky Reach Dam and at other projects with a wide range of TDG management attributes. In addition to a review of physical data, the theoretical basis for TDG gas transfer and best engineering judgment was employed to


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develop an assessment of the potential TDG management of various alternatives to Rocky Reach Dam. The scheduling of standard powerhouse flow does not change the TDG content in the Columbia River. However, spilling water at Rocky Reach dam can result in changes to the TDG loading in the Columbia River. Therefore, the most reliable method to not impact the TDG loading in the Columbia River at Rocky Reach Dam would be to reduce or eliminate spill. Spill can be caused by the need to pass water in excess of the powerhouse hydraulic capacity. This involuntary spill can be limited by water control measures that prevent surplus flows downstream of Grand Coulee Dam and by careful planning of turbine unit outages and related activities. The consequences of having all 11 turbines available for operation versus only 10 turbines during a total river flow of 250 kcfs is demonstrated by cases 36 and 126 listed in Table A1 for forebay TDG levels of 110% and a spill policy of 10 percent. The full powerhouse capacity would require a spill of 30 kcfs and result in an increase in the average Columbia River TDG to 111.3 percent. If only 10 turbine were available during these same events, a spill of 50 kcfs would be required resulting in an average TDG saturation of 113.1 percent. Voluntary spillway operations are scheduled for the purposes of promoting juvenile fish survival, adult guidance efficiency, and limiting TDG uptake. The need for voluntary spill has been reduced with the completion of the juvenile bypass system at Rocky Reach Dam. Efforts to improve fish guidance will continue to lessen the reliance on spill to meet biological fish passage objectives. A reduction in the voluntary spill policy from 25 to 15 percent during river flows of 200 kcfs and forebay levels of 110% saturation are listed in Table 1 (cases 140 and 155) . The maximum TDG saturation in spill was reduced from 118.3 percent to 115.6 percent for the smaller voluntary spill policy, while the average cross sectional TDG saturation was reduced from 113.3 to 111.7 percent. This is nearly the same level of enhancement provided by maintaining full powerhouse capacity but the frequency of occurrence of flows on the order of 200 kcfs is much higher than the forced spill flow of 250 kcfs. Therefore, a voluntary spill policy reduction will have a much larger impact on TDG levels in the Columbia River than efforts to maintain adequate hydraulic capacity. The impact of Rocky Reach spill on the TDG loading in the Mid-Columbia River will depend upon the spill pattern and magnitude, powerhouse flow, and the upstream TDG level. If the TDG content in spill is greater than ambient forebay TDG levels, a net increase in the average TDG saturation will result. However, it is not uncommon for the TDG content in spill at Rocky Reach to be less than the ambient forebay levels resulting in a decrease in the average TDG saturation in the Columbia River. A spill of 20 kcfs will result in a maximum TDG saturation in spill of about 114.2 percent. If forebay TDG levels are equal to the TDG waiver limit of 115.0 percent, this spill of 20 kcfs would result in a reduction in the TDG loading in the Columbia River. The net impact on average TDG levels in the Columbia River are generally small at Rocky Reach Dam during period of voluntary spill because of the small percentage of river flow impacted by spill.


45

The limited channel width of the Columbia River required the spillway and stilling basin at Rocky Reach Dam to take on a unique design aimed at efficiently dissipating the energy contained in spill over a short distance. The spillway and stilling basin include hydraulic structures like the nappe deflector, continuous baffle, and high stilling basin end sill that provides sufficient energy dissipation over the short length of the stilling basin. These hydraulic structures have the unintended impact of moderating the TDG exchange characteristics at Rocky Reach Dam. The combination of efficient energy dissipation in a shallow stilling basin with an end sill that produces a surface oriented jet entering the adjoining tailwater channel result in TDG pressures that are similar to projects with retrofitted TDG abatement structures. The maximum TDG saturation observed in spill below the stilling basin did not exceed 120 percent for spill as high as 58 kcfs using the standard spill pattern at Rocky Reach Dam based on observations conducted during the 2002 near-field TDG exchange study. If this TDG response can be applied for higher river flows, the tailwater TDG criteria of 120 percent will not be exceeded for river flows up to the 7Q10 discharge assuming the availability of at least 10 turbines. Under these conditions, tailwater TDG levels above 120 percent would have to originate from some upstream source of TDG pressure. The maximum TDG saturation in spill varied linearly with total spill discharge. The maximum TDG saturation in spill ranged from 113 percent during a standard spill of 10 kcfs to 119.3 percent during a standard spill of 58 kcfs. The TDG monitoring of project releases is currently located 4.4 miles downstream from the project near mid-river. This station is located in the mixing zone of powerhouse and spillway flows and can often provide a reasonable estimate of average river TDG conditions. Alternative tailwater sampling stations were evaluated during the TDG exchange study. The stations located immediately below the stilling basin were frequently in aerated flow and provided inconsistent measures of TDG pressures in spill. Stations located near the juvenile bypass outfall were consistently outside of the zone of aerated flow and would meet monitoring criteria recommended in the Mid-Columbia river TMDL for TDG and reflect the maximum TDG pressures in spill. The merits of sampling TDG levels at alternative tailwaters monitoring stations downstream of Rocky Reach Dam will depend upon the stated objectives of the sampling program. The location of this sampling station will be critical for quantifying the performance of alternative TDG management programs. For instance, the performance of a TDG management program aimed at reducing the average TDG pressures in the river could not be evaluated effectively with a tailwater TDG station sampling only the conditions in spill. The TDG pressures generated in spill at projects located throughout the Columbia River basin are commonly related to the spill pattern applied. Spill operations that employ a uniform spill pattern using the entire spillway have frequently been found to produce lower levels of TDG saturation when compared to the application of a bulk spill pattern where spill is concentrated over a portion of the spillway. Observations conducted during two spill events at Rocky Reach Dam with spill uniformly distributed over bays 2-12 support a reduction in the average TDG saturation by as much as 2 percent saturation compared to the standard spill pattern. A comprehensive series of estimates of TDG


46

exchange at Rocky Reach Dam using this alternative pattern were not prepared due to limited information. This reduction in TDG exchange was noted in the average TDG pressures in the Columbia River and not in the maximum TDG pressure in spill. Additional field test are required to further quantify the TDG exchange benefits of the uniform spill pattern on bays 2-12 at Rocky Reach Dam. The potential TDG abatement of structural modifications to Rocky Reach Dam was considered in this evaluation. The assessment of structural modifications on TDG exchange was based on observations of TDG exchange at other projects where spillway modifications have been installed or where the physical characteristics mimic the alternatives recommended for further consideration. Most of the structural alternatives were identified to exhibit limited potential to effectively manage TDG saturation at Rocky Reach Dam primarily because of the relatively low rates of TDG exchange associated with current spill operations. The wide application of spillway flow deflectors as a TDG management alternative on the Snake and Columbia Rivers has proven effective when preventing plunging flow in a deep stilling basin. The current TDG exchange performance at Rocky Reach Dam is comparable and in some cases superior to projects with spillway flow deflectors. The application of spillway flow deflectors to Rocky Reach Dam could potentially increase the TDG loading during spill because of the large entrainment demand associated with this alternative and the delivery of aerated flow into the deeper tailwater channel. Alternatives involving raising the stilling basin elevation at Rocky Reach Dam were also judged to provide limited benefits to manage TDG saturation. The controlled spill over bays 9-12 which has a higher stilling basin floor than other bays, delivered spill containing higher TDG pressures than comparable spill over bays 2-8. The TDG performance at The Dalles Dam that has a conventional stilling basin with a stilling basin depth similar to flow conditions at Rocky Reach Dam, generated considerable higher TDG levels even when extrapolating the TDG response to shallower depths of flow. Raising the tailwater channel was judged to have a small potential to reduce the TDG loading at Rocky Reach Dam. The surface oriented jet exiting the stilling basin as generated by the slotted end sill will reduce the importance of tailwater channel elevation on the TDG exchange process. Removal of the spillway nappe deflectors that promote energy dissipation in the stilling basin, was identified as having minimal influence on TDG exchange at Rocky Reach Dam. The structural measures which were identified as having potential to further manage TDG saturation at Rocky Reach Dam were the entrainment cutoff wall and spillway flow deflectors with a raised tailwater channel. A portion of the powerhouse release from Rocky Reach Dam encounters the aerated flow conditions generated during spill. The exposure of powerhouse flow to entrained air results in a larger volume of water being directly impacted by the mass exchange process. The entrainment of powerhouse flow was estimated from the results of the 2002 near-field TDG exchange study and used to estimate the TDG benefits associated with an entrainment cutoff wall. The reduction to


47

the average TDG saturation in the Columbia River below the project was estimated to range up to 2.6 percent saturation when compared to current conditions. This alternative would have little influence on the maximum TDG saturation attained in spill but would reduce the TDG loading to the Columbia River and on TDG levels delivered to downstream projects. The amount of TDG abatement is smaller during voluntary spill conditions and goes to zero as the spill become small. The TDG exchange properties at Ice Harbor Dam have consistently exhibited the lowest TDG exchange properties of dams actively spilling for fish passage in the Columbia River Basin. The combination of spillway flow deflectors and a shallow tailwater channel has been identified as the cause for the low rates of TDG exchange. If the spillway, stilling basin, and adjoining tailwater channel at Rocky Reach Dam were rebuilt to resemble the conditions at Ice Harbor Dam, an improvement to TDG management could be achieved. However, the benefits of TDG reduction were estimated to range up to 2.7 percent saturation or similar to the impacts attributed to an entrainment cutoff wall. The influence of all the operational and structural TDG management alternatives will need to consider the impacts to other beneficial uses of the river prior to further consideration for adoption.


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References CENPD 1998.“1998 Total Dissolved Gas Annual Report,” US Army Corps of Engineers,

Northwestern Division, North Pacific Region.

CENWP-NWW 1996.“Dissolved Gas Abatement Study Phase I,” Technical Report, US Army Engineer Districts-Portland and Walla Walla, Portland, OR and Walla Walla, WA, respectively

CEERDC 2003, “Total Dissolved Gas Exchange at Lower Granite Dam, 2002 Spill Season”, Memorandum for Record, June 16, 2003, US Army Engineer Research and Development Center, Vicksburg MS Colt, John 1984.“Computation of dissolved gas concentrations in water as functions of

temperature, salinity, and pressure,” American Fisheries Society Special Publication No. 14.

MWH 2003. “Gas Abatement Techniques at Rocky Reach Hydroelectric Project,” Prepared for Chelan County Public Utility District No. 1.

Orlins, J. J. and Gulliver, J. S. 2000. “Dissolved gas supersaturation downstream of a spillway. II: Computational model,’’ Journal of Hydraulic Research, 38(2), 151–159.

Rindels, A. J., and Gulliver, J. S. 1989.“Measurements of Oxygen Transfer at Spillways and Overfalls,” St. Anthony Falls Hydraulic Laboratory Project Report No. 226, University of Minnesota, Minneapolis, MN

Schneider, M. L. and Wilhelms, S.C 1996."Near-Field Study of Total Dissolved Gas in the Dalles Spillway Tailwater”, CEWES-CS-L Memorandum for Record, December 16, 1996, US Army Engineer Waterways Experiment Station, Vicksburg MS.

Schneider, M. L. and Wilhelms, S.C. 1997." Documentation and Analysis of the Near-Field Ice Harbor Tailwater Study, June 27-28, 1996 ," CEWES-HS-L Memorandum for Record, January 27, 1997, US Army Engineer Waterways Experiment Station, Vicksburg MS.

Schneider, M. L. and Wilhelms, S.C. 1998a." Total dissolved gas exchange during spillway releases at Little Goose Dam, February 20-22, 1998," CEWES-HS-L Memorandum for Record, December 10, 1998, US Army Engineer Waterways Experiment Station, Vicksburg MS.


49

Schneider, M. L., and Wilhelms, S. C. 1998b.“ Near-Field Study of Total Dissolved Gas in The Dalles Spillway Tailwater,” CEWES-HS-L, Memorandum for Record dated December 16, 1998, US Army Waterways Experiment Station, Coastal and Hydraulics Laboratory, Vicksburg, MS

Schneider, M.L. and Wilhelms, S.C. 1998c.“Proposed Ice Harbor Raised Tailrace Channel _ Total Dissolved Gas Estimates,” CEWES-CS-L Memorandum for Record dated 26 October 1998, US Army Waterways Experiment Station, Vicksburg, MS.

Schneider, M. L. and Carroll, J.C. 1999." TDG exchange during spillway releases at Chief Joseph Dam, near-field study, June 6-10, 1999," CE-ERDCCR-F, US Army Engineer Waterways Experiment Station, Vicksburg MS.

Schneider, M. L. 2003. “Total Dissolved Gas Exchange During Spillway Operations at Rocky Reach Dam, April 26-May 3, 2002,” Report to Public Utility District No. 1 of Chelan County, Wenatchee, WA USACE 2002.“Dissolved gas abatement study, final report,” US Army Engineer, District,

Portland and Walla Walla, North Pacific Region, Portland OR.

Wilhelms, S. C. 1997.“Self-Aerated Spillway Flow,” A Thesis in Partial Fulfillment for the degree pf Doctor of Philosophy, Department of Civil Engineering, University of Minnesota, Minneapolis, MN

Wilhelms, S. C. and Gulliver, J. S. 1994.“Self-Aerated Flow on Corps of Engineers Spillways”, TR W-94-2, US Army Corps of Engineers.

Wilhelms, S. C., Schneider, M. L., and Howington, S. E. 1987.“Improvement of Hydropower Release Dissolved Oxygen with Turbine Venting,” Technical Report E-87-3, US Army Engineer Waterways Experiment Station, Vicksburg, MS

Wilhelms, S.C. and Schneider, M. L. 1998." Documentation and Analysis of the Ice Harbor Near-Field Tailwater Study, March 1998, Post-Deflector Installation”, CEWES-CS-L Memorandum for Record, November 27, 1998, US Army Engineer Waterways Experiment Station, Vicksburg MS.


50

Figure 1. Aerated spillway flow at Rocky Reach Dam, May 2, 2002.

(Spill 47.6 kcfs during a standard spill pattern, generation flow 113 kcfs)


51

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

1011 12

32

1

45

67 8

9

Powerh

ouse

SpillwayStilling Basin

End Sill

Rocky Reach Dam

Tailrace Channel

Columbia River

EastFishLadder

West

Fish

Ladde

r

Figure 2. Aerial view of the Rocky Reach powerhouse and spillway.


52

Figure 3. Profile view of Rocky Reach spillway and stilling basin (section S3 profile).


53

590

580

580 600

S5S4 S4S2 S2 S2 S4

S1

Figure 4. Plan view of Rocky Reach spillway and stilling basin.


54

Figure 5. Rocky Reach tailwater channel bathymetry.

Figure 5. Rocky Reach tailwater channel bathymetry.


55

FB1

RockyReachDam

RRHDTD

SBP3SBP2

SBP1

FOP4

FOP3

FOP2FOP1

RockyReachDam

1

12

35

710

Figure 6. Near-field TDG sampling stations at Rocky Reach Dam.

Juvenile Fish

Bypass Outfall

Figure 6. Near-field TDG sampling stations at Rocky Reach Dam.


56

RockyReachDam

FOP4

FOP3

FOP2FOP1

LDP5LDP4

LDP3

LDP2 LDP1

Figure 7. TDG instrument deployment at Rocky Reach Dam, April 26-May 2, 2002.

Juvenile Fish

Bypass Outfall

Figure 7. TDG instrument deployment at Rocky Reach Dam, April 26-May 2, 2002.


57

105

110

115

120

125

130

135

140

4/26 4/27 4/28 4/29 4/30 5/1 5/2 5/3 5/4

TD

G S

atu

ratio

n (%

)

-400.0

-300.0

-200.0

-100.0

0.0

100.0

200.0

300.0

Flo

w (

kcfs

)

FBP1 SBP1 FOP1 LDP1 FMP1 RRDW Total Flow Total Spill

21

3 45

67

8

9

10

11

12

1314

15

1617

18

19

2021

2223

24 25

2627

2829

30 3132

33

34

Event Spill Pattern KeyColor Coded

Std Pattern Bays 2-5 Bays 9-12 Bays 5-8Bays 2-8 Bays 2-12

Figure 8. TDG saturation for left bank or spillway side station and project operations at Rocky Reach Dam, April 29-May 2, 2002.


58

y = 1.0551x - 5.8202R2 = 0.9674

110

115

120

125

130

110 115 120 125 130

TDG Saturation @ FOP1

TD

G S

atu

rati

on

@ S

BP

1SBP1Linear (SBP1)

Figure 9. Total Dissolved Gas Saturation at stations FOP1 and SBP1 during April 26-May 3, 2002 (Includes spill events with a duration of at least 1 hr excluding uniform spill over bays 9-12).


59

y = 0.1509x + 111.61R2 = 0.8594

y = 0.2573x + 109.67R2 = 0.816

y = 0.4024x + 108.17R2 = 0.9769

y = 0.3777x + 105.43R2 = 0.9889

110.0

115.0

120.0

125.0

130.0

0 10 20 30 40 50 60 70

Spill Discharge (kcfs)

To

tal D

isso

lved

Gas

Sat

ura

tion

(%)

Bays 2-12Bays 2-5Bays 2-8Bays 5-8Bays 9-12StdLinear (Std)Linear (Bays 2-5)Linear (Bays 9-12)Linear (Bays 2-8)

Figure 10. Maximum TDG saturation below the stilling basin at station SBP1 as a function of total spill flow, Rocky Reach Dam, April 26-May 3, 2002.


60

y = 0.2142x + 111.84R2 = 0.9569

y = 0.1355x + 111.5R2 = 0.866

y = 0.1835x + 111.14R2 = 0.9532

y = 0.2031x + 110.46R2 = 0.9327

110.0

115.0

120.0

125.0

130.0

0 10 20 30 40 50 60 70

Spillway Discharge (kcfs)

To

tal D

isso

lved

Gas

Sat

ura

tion

(%)

Bays 2-12

Bays 2-5Bays 9-12stdBays 2-8Linear (Bays 9-12)Linear (std)Linear (Bays 2-5)Linear (Bays 2-8)

Figure 11. Maximum TDG saturation below the stilling basin at station FOP1 as a function of total spill flow, Rocky Reach Dam, April 26-May 3, 2002.


61

105

110

115

120

125

130

135

140

4/26 4/27 4/28 4/29 4/30 5/1 5/2 5/3 5/4

TD

G S

atura

tion (%

)

-400.0

-300.0

-200.0

-100.0

0.0

100.0

200.0

300.0

Flo

w (k

cfs)

LD-avg FB LD-Calc RRDW FOP1l SBP1 Qtotal Qspill Qent

21

3 45

67

8

9

10

11

12

1314

15

1617

18

19

2021

2223

24 25

2627

2829

30 3132

33

34



Figure 12. Rocky Reach hourly operations and observed TDG saturation at stations SBP1. FOP1, FB, RRDW and Transect LD, April 26-May 3, 2002. (note: LD-avg was determined by flow weighting TDG levels from five stations and LD-calc was based

on a mass conservation statement with no added mass component)


62

105

110

115

120

125

130

135

140

4/26 4/27 4/28 4/29 4/30 5/1 5/2 5/3 5/4

TD

G S

atura

tion (%

)

-400.0

-300.0

-200.0

-100.0

0.0

100.0

200.0

300.0

Flo

w (k

cfs)

LD-avg FB LD-Calc RRDW FOP1l SBP1 Qtotal Qspill Qent

Figure 13. Rocky Reach hourly operations and observed TDG saturation at stations SBP1, FOP1, FB,

21

3 45

67

8

9

10

11

12

1314

15

1617

18

19

2021

2223

24 25

2627

2829

30 3132

33

34



Figure 13. Rocky Reach hourly operations and observed TDG saturation at stations SBP1, FOP1, FB, RRDW and Transect LD, April 26-May3, 2002. (note: LD-avg was determined by flow weighting TDG levels from five stations and LD-calc was based

on mass conservation statement with an added mass component equal to a fraction of the generation discharge)


63

105

110

115

120

125

130

135

140

4/30/02 0:00 4/30/02 6:00 4/30/02 12:00 4/30/02 18:00 5/1/02 0:00 5/1/02 6:00 5/1/02 12:00 5/1/02 18:00 5/2/02 0:00

TD

G S

atu

ratio

n (%

)

-400

-300

-200

-100

0

100

200

300

Flo

w (k

cfs)

LDP1 LDP2 LDP3 LDP4 LDP5 FBP1 LD-Avg Qtotal Qspill

19

2021

2223

24

2526

2728

29



Figure 14. TDG saturation at the loading dock (LD) transect and project operations at Rocky Reach Dam, April 30-May 1, 2002.


64

Figure 15. Spillway flow deflector and stilling basin circulation pattern.


65

100.0

105.0

110.0

115.0

120.0

125.0

130.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Specific Spillway Discharge (kcfs/bay)

TD

G S

atu

rati

on

(%

)

RRH

LWG-RSW

LWG-STD

Figure 16. Total dissolved gas saturation as a function of specific spillway discharge at Rocky Reach and Lower Granite Dams (Note: LWG-RSW Lower Granite spill pattern with removable spillway weir, LWG-STD Lower Granite spill with standard spill

pattern)


66

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

1011 12

32

1

45

67 8

9

Powerh

ouse


End Sill

Rocky Reach Dam

Tailrace Channel

Columbia River

EastFishLadderW

estFis

hLad

der

Entra

inmen

t Cuto

ff W

all

Figure 17. Aerial view of the Rocky Reach powerhouse and spillway with entrainment cutoff wall

(dashed line).


67

y = 1.0939x + 97.291R2 = 0.8972

y = 0.693x + 99.385R2 = 0.4276

100

105

110

115

120

125

130

135

15 20 25 30 35

Stilling Basin Depth (ft)

TD

G S

atu

ratio

n (%

)

TDA-JP RRH-STD RRH U9-12 Linear (TDA-JP) Linear (RRH-STD)

Figure 18. Total Dissolved Gas Saturation in Spillway Flows as a function of Stilling Basin Depth at The Dalles Dam and Rocky Reach Dam (TDA-JP The Dalles Dam Juvenile Spill Pattern 2000, RRH-STD Rocky Reach Dam Standard Spill Pattern 2002,

RRH U9-12 Rocky Reach Dam Uniform Spill Pattern over bays 9-12, 2002)


68

100

105

110

115

120

125

130

0 5 10 15 20 25 30 35 40

Tailwater Channel Depth (ft)

TDG

Sat

urat

ion

(%)

IHRRRH-STDTDA-JP

Figure 19. Total Dissolved Gas Saturation as a function of Tailwater Channel Depth at Rocky Reach, Ice Harbor, and The Dalles Dams, (RRH standard pattern 2002, IHR Standard and Bulk Pattern, 2004, TDA Juvenile patter 2000)


69

y = 3E-05x2 + 0.052x + 611.57R2 = 0.9842

610

612

614

616

618

620

622

624

626

628

630

0 50 100 150 200 250 300

Total River Flow (kcfs)

Tai

lwat

er E

leva

tio

n (

ft)

Figure 20. Tailwater Elevation versus Total River Flow at Rocky Reach Dam, 2002

(note: Flow duration of 2 hours of greater)


70

100.0

105.0

110.0

115.0

120.0

125.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Specific Spillway Discharge (kcfs/bay)

TD

G S

atu

ratio

n (

%)

rrhihr

Figure 21. Total Dissolved Gas Saturation as a function of Specific Spillway Discharge at Rocky Reach and Ice Harbor Dams, (RRH standard pattern 2002, IHR Standard and Bulk Pattern, 2004)


71

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

1011 12

32

1

45

67 8

9

Powerh

ouse


Rocky Reach Dam

Tailrace Channel

Columbia RiverWest

FishLad

der

EastFishLadder

End Sill

Raised Tailwater

Channel El. 608.

Figure 22. Aerial view of the Rocky Reach powerhouse and spillway with a raised tailrace channel.

Appendix A

Table A1. Total Dissolved Gas Saturation estimate as a function of structural alternative, spill policy, river flow, and background TDG saturation for Rocky Reach Dam

Case Structure Alternative1 Spill Policy2 (Qsp/Qtotal)

Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 1 Base 0.00 220 150 150.0 0.0 0.0 105 111.5 105.0 0.0 2 Base 0.00 220 200 200.0 0.0 0.0 105 111.5 105.0 0.0 3 Base 0.00 220 250 220.0 30.0 30.0 105 115.6 107.5 2.5 4 Base 0.00 220 150 150.0 0.0 0.0 110 111.5 110.0 0.0 5 Base 0.00 220 200 200.0 0.0 0.0 110 111.5 110.0 0.0 6 Base 0.00 220 250 220.0 30.0 30.0 110 115.6 111.3 1.3 7 Base 0.00 220 150 150.0 0.0 0.0 115 111.5 115.0 0.0 8 Base 0.00 220 200 200.0 0.0 0.0 115 111.5 115.0 0.0 9 Base 0.00 220 250 220.0 30.0 30.0 115 115.6 115.1 0.1

10 Base 0.00 220 150 150.0 0.0 0.0 120 111.5 120.0 0.0 11 Base 0.00 220 200 200.0 0.0 0.0 120 111.5 120.0 0.0 12 Base 0.00 220 250 220.0 30.0 30.0 120 115.6 118.9 -1.1 13 Base 0.00 220 150 150.0 0.0 0.0 125 111.5 125.0 0.0 14 Base 0.00 220 200 200.0 0.0 0.0 125 111.5 125.0 0.0 15 Base 0.00 220 250 220.0 30.0 30.0 125 115.6 122.7 -2.3 16 Base 0.05 220 150 142.5 7.5 7.5 105 112.5 105.8 0.8 17 Base 0.05 220 200 190.0 10.0 10.0 105 112.9 105.8 0.8 18 Base 0.05 220 250 220.0 30.0 30.0 105 115.6 107.5 2.5 19 Base 0.05 220 150 142.5 7.5 7.5 110 112.5 110.3 0.3 20 Base 0.05 220 200 190.0 10.0 10.0 110 112.9 110.3 0.3 21 Base 0.05 220 250 220.0 30.0 30.0 110 115.6 111.3 1.3 22 Base 0.05 220 150 142.5 7.5 7.5 115 112.5 114.8 -0.2



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 23 Base 0.05 220 200 190.0 10.0 10.0 115 112.9 114.8 -0.2 24 Base 0.05 220 250 220.0 30.0 30.0 115 115.6 115.1 0.1 25 Base 0.05 220 150 142.5 7.5 7.5 120 112.5 119.3 -0.7 26 Base 0.05 220 200 190.0 10.0 10.0 120 112.9 119.3 -0.7 27 Base 0.05 220 250 220.0 30.0 30.0 120 115.6 118.9 -1.1 28 Base 0.05 220 150 142.5 7.5 7.5 125 112.5 123.8 -1.2 29 Base 0.05 220 200 190.0 10.0 10.0 125 112.9 123.8 -1.2 30 Base 0.05 220 250 220.0 30.0 30.0 125 115.6 122.7 -2.3 31 Base 0.10 220 150 135.0 15.0 15.0 105 113.5 106.7 1.7 32 Base 0.10 220 200 180.0 20.0 20.0 105 114.2 106.8 1.8 33 Base 0.10 220 250 220.0 30.0 30.0 105 115.6 107.5 2.5 34 Base 0.10 220 150 135.0 15.0 15.0 110 113.5 110.7 0.7 35 Base 0.10 220 200 180.0 20.0 20.0 110 114.2 110.8 0.8 36 Base 0.10 220 250 220.0 30.0 30.0 110 115.6 111.3 1.3 37 Base 0.10 220 150 135.0 15.0 15.0 115 113.5 114.7 -0.3 38 Base 0.10 220 200 180.0 20.0 20.0 115 114.2 114.8 -0.2 39 Base 0.10 220 250 220.0 30.0 30.0 115 115.6 115.1 0.1 40 Base 0.10 220 150 135.0 15.0 15.0 120 113.5 118.7 -1.3 41 Base 0.10 220 200 180.0 20.0 20.0 120 114.2 118.8 -1.2 42 Base 0.10 220 250 220.0 30.0 30.0 120 115.6 118.9 -1.1 43 Base 0.10 220 150 135.0 15.0 15.0 125 113.5 122.7 -2.3 44 Base 0.10 220 200 180.0 20.0 20.0 125 114.2 122.8 -2.2 45 Base 0.10 220 250 220.0 30.0 30.0 125 115.6 122.7 -2.3 46 Base 0.15 220 150 127.5 22.5 22.5 105 114.5 107.9 2.9 47 Base 0.15 220 200 170.0 30.0 30.0 105 115.6 108.2 3.2 48 Base 0.15 220 250 212.5 37.5 37.5 105 116.6 108.5 3.5



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 49 Base 0.15 220 150 127.5 22.5 22.5 110 114.5 111.4 1.4 50 Base 0.15 220 200 170.0 30.0 30.0 110 115.6 111.7 1.7 51 Base 0.15 220 250 212.5 37.5 37.5 110 116.6 112.0 2.0 52 Base 0.15 220 150 127.5 22.5 22.5 115 114.5 114.9 -0.1 53 Base 0.15 220 200 170.0 30.0 30.0 115 115.6 115.2 0.2 54 Base 0.15 220 250 212.5 37.5 37.5 115 116.6 115.5 0.5 55 Base 0.15 220 150 127.5 22.5 22.5 120 114.5 118.4 -1.6 56 Base 0.15 220 200 170.0 30.0 30.0 120 115.6 118.7 -1.3 57 Base 0.15 220 250 212.5 37.5 37.5 120 116.6 119.0 -1.0 58 Base 0.15 220 150 127.5 22.5 22.5 125 114.5 121.9 -3.1 59 Base 0.15 220 200 170.0 30.0 30.0 125 115.6 122.2 -2.8 60 Base 0.15 220 250 212.5 37.5 37.5 125 116.6 122.5 -2.5 61 Base 0.25 220 150 112.5 37.5 22.7 105 116.6 109.6 4.6 62 Base 0.25 220 200 150.0 50.0 32.0 105 118.3 110.4 5.4 63 Base 0.25 220 250 187.5 62.5 41.4 105 120.0 111.2 6.2 64 Base 0.25 220 150 112.5 37.5 22.7 110 116.6 112.6 2.6 65 Base 0.25 220 200 150.0 50.0 32.0 110 118.3 113.4 3.4 66 Base 0.25 220 250 187.5 62.5 41.4 110 120.0 114.1 4.1 67 Base 0.25 220 150 112.5 37.5 22.7 115 116.6 115.6 0.6 68 Base 0.25 220 200 150.0 50.0 32.0 115 118.3 116.3 1.3 69 Base 0.25 220 250 187.5 62.5 41.4 115 120.0 117.1 2.1 70 Base 0.25 220 150 112.5 37.5 22.7 120 116.6 118.6 -1.4 71 Base 0.25 220 200 150.0 50.0 32.0 120 118.3 119.3 -0.7 72 Base 0.25 220 250 187.5 62.5 41.4 120 120.0 120.0 0.0 73 Base 0.25 220 150 112.5 37.5 22.7 125 116.6 121.6 -3.4 74 Base 0.25 220 200 150.0 50.0 32.0 125 118.3 122.2 -2.8



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 75 Base 0.25 220 250 187.5 62.5 41.4 125 120.0 122.9 -2.1 76 Base 0.35 220 150 97.5 52.5 18.9 105 118.6 111.5 6.5 77 Base 0.35 220 200 130.0 70.0 27.0 105 121.0 112.8 7.8 78 Base 0.35 220 250 162.5 87.5 35.2 105 123.4 114.0 9.0 79 Base 0.35 220 150 97.5 52.5 18.9 110 118.6 114.1 4.1 80 Base 0.35 220 200 130.0 70.0 27.0 110 121.0 115.3 5.3 81 Base 0.35 220 250 162.5 87.5 35.2 110 123.4 116.6 6.6 82 Base 0.35 220 150 97.5 52.5 18.9 115 118.6 116.7 1.7 83 Base 0.35 220 200 130.0 70.0 27.0 115 121.0 117.9 2.9 84 Base 0.35 220 250 162.5 87.5 35.2 115 123.4 119.1 4.1 85 Base 0.35 220 150 97.5 52.5 18.9 120 118.6 119.3 -0.7 86 Base 0.35 220 200 130.0 70.0 27.0 120 121.0 120.5 0.5 87 Base 0.35 220 250 162.5 87.5 35.2 120 123.4 121.6 1.6 88 Base 0.35 220 150 97.5 52.5 18.9 125 118.6 122.0 -3.0 89 Base 0.35 220 200 130.0 70.0 27.0 125 121.0 123.1 -1.9 90 Base 0.35 220 250 162.5 87.5 35.2 125 123.4 124.2 -0.8 91 Base 0.00 200 150 150.0 0.0 0.0 105 111.5 105.0 0.0 92 Base 0.00 200 200 200.0 0.0 0.0 105 111.5 105.0 0.0 93 Base 0.00 200 250 200.0 50.0 44.5 105 118.3 110.0 5.0 94 Base 0.00 200 150 150.0 0.0 0.0 110 111.5 110.0 0.0 95 Base 0.00 200 200 200.0 0.0 0.0 110 111.5 110.0 0.0 96 Base 0.00 200 250 200.0 50.0 44.5 110 118.3 113.1 3.1 97 Base 0.00 200 150 150.0 0.0 0.0 115 111.5 115.0 0.0 98 Base 0.00 200 200 200.0 0.0 0.0 115 111.5 115.0 0.0 99 Base 0.00 200 250 200.0 50.0 44.5 115 118.3 116.2 1.2 100 Base 0.00 200 150 150.0 0.0 0.0 120 111.5 120.0 0.0



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 101 Base 0.00 200 200 200.0 0.0 0.0 120 111.5 120.0 0.0 102 Base 0.00 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 103 Base 0.00 200 150 150.0 0.0 0.0 125 111.5 125.0 0.0 104 Base 0.00 200 200 200.0 0.0 0.0 125 111.5 125.0 0.0 105 Base 0.00 200 250 200.0 50.0 44.5 125 118.3 122.5 -2.5 106 Base 0.05 200 150 142.5 7.5 7.5 105 112.5 105.8 0.8 107 Base 0.05 200 200 190.0 10.0 10.0 105 112.9 105.8 0.8 108 Base 0.05 200 250 200.0 50.0 44.5 105 118.3 110.0 5.0 109 Base 0.05 200 150 142.5 7.5 7.5 110 112.5 110.3 0.3 110 Base 0.05 200 200 190.0 10.0 10.0 110 112.9 110.3 0.3 111 Base 0.05 200 250 200.0 50.0 44.5 110 118.3 113.1 3.1 112 Base 0.05 200 150 142.5 7.5 7.5 115 112.5 114.8 -0.2 113 Base 0.05 200 200 190.0 10.0 10.0 115 112.9 114.8 -0.2 114 Base 0.05 200 250 200.0 50.0 44.5 115 118.3 116.2 1.2 115 Base 0.05 200 150 142.5 7.5 7.5 120 112.5 119.3 -0.7 116 Base 0.05 200 200 190.0 10.0 10.0 120 112.9 119.3 -0.7 117 Base 0.05 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 118 Base 0.05 200 150 142.5 7.5 7.5 125 112.5 123.8 -1.2 119 Base 0.05 200 200 190.0 10.0 10.0 125 112.9 123.8 -1.2 120 Base 0.05 200 250 200.0 50.0 44.5 125 118.3 122.5 -2.5 121 Base 0.10 200 150 135.0 15.0 15.0 105 113.5 106.7 1.7 122 Base 0.10 200 200 180.0 20.0 20.0 105 114.2 106.8 1.8 123 Base 0.10 200 250 200.0 50.0 44.5 105 118.3 110.0 5.0 124 Base 0.10 200 150 135.0 15.0 15.0 110 113.5 110.7 0.7 125 Base 0.10 200 200 180.0 20.0 20.0 110 114.2 110.8 0.8 126 Base 0.10 200 250 200.0 50.0 44.5 110 118.3 113.1 3.1



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 127 Base 0.10 200 150 135.0 15.0 15.0 115 113.5 114.7 -0.3 128 Base 0.10 200 200 180.0 20.0 20.0 115 114.2 114.8 -0.2 129 Base 0.10 200 250 200.0 50.0 44.5 115 118.3 116.2 1.2 130 Base 0.10 200 150 135.0 15.0 15.0 120 113.5 118.7 -1.3 131 Base 0.10 200 200 180.0 20.0 20.0 120 114.2 118.8 -1.2 132 Base 0.10 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 133 Base 0.10 200 150 135.0 15.0 15.0 125 113.5 122.7 -2.3 134 Base 0.10 200 200 180.0 20.0 20.0 125 114.2 122.8 -2.2 135 Base 0.10 200 250 200.0 50.0 44.5 125 118.3 122.5 -2.5 136 Base 0.15 200 150 127.5 22.5 22.5 105 114.5 107.9 2.9 137 Base 0.15 200 200 170.0 30.0 30.0 105 115.6 108.2 3.2 138 Base 0.15 200 250 200.0 50.0 44.5 105 118.3 110.0 5.0 139 Base 0.15 200 150 127.5 22.5 22.5 110 114.5 111.4 1.4 140 Base 0.15 200 200 170.0 30.0 30.0 110 115.6 111.7 1.7 141 Base 0.15 200 250 200.0 50.0 44.5 110 118.3 113.1 3.1 142 Base 0.15 200 150 127.5 22.5 22.5 115 114.5 114.9 -0.1 143 Base 0.15 200 200 170.0 30.0 30.0 115 115.6 115.2 0.2 144 Base 0.15 200 250 200.0 50.0 44.5 115 118.3 116.2 1.2 145 Base 0.15 200 150 127.5 22.5 22.5 120 114.5 118.4 -1.6 146 Base 0.15 200 200 170.0 30.0 30.0 120 115.6 118.7 -1.3 147 Base 0.15 200 250 200.0 50.0 44.5 120 118.3 119.3 -0.7 148 Base 0.15 200 150 127.5 22.5 22.5 125 114.5 121.9 -3.1 149 Base 0.15 200 200 170.0 30.0 30.0 125 115.6 122.2 -2.8 150 Base 0.15 200 250 200.0 50.0 44.5 125 118.3 122.5 -2.5 151 Base 0.25 200 150 112.5 37.5 22.7 105 116.6 109.6 4.6 152 Base 0.25 200 200 150.0 50.0 32.0 105 118.3 110.4 5.4



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 153 Base 0.25 200 250 187.5 62.5 41.4 105 120.0 111.2 6.2 154 Base 0.25 200 150 112.5 37.5 22.7 110 116.6 112.6 2.6 155 Base 0.25 200 200 150.0 50.0 32.0 110 118.3 113.4 3.4 156 Base 0.25 200 250 187.5 62.5 41.4 110 120.0 114.1 4.1 157 Base 0.25 200 150 112.5 37.5 22.7 115 116.6 115.6 0.6 158 Base 0.25 200 200 150.0 50.0 32.0 115 118.3 116.3 1.3 159 Base 0.25 200 250 187.5 62.5 41.4 115 120.0 117.1 2.1 160 Base 0.25 200 150 112.5 37.5 22.7 120 116.6 118.6 -1.4 161 Base 0.25 200 200 150.0 50.0 32.0 120 118.3 119.3 -0.7 162 Base 0.25 200 250 187.5 62.5 41.4 120 120.0 120.0 0.0 163 Base 0.25 200 150 112.5 37.5 22.7 125 116.6 121.6 -3.4 164 Base 0.25 200 200 150.0 50.0 32.0 125 118.3 122.2 -2.8 165 Base 0.25 200 250 187.5 62.5 41.4 125 120.0 122.9 -2.1 166 Base 0.35 200 150 97.5 52.5 18.9 105 118.6 111.5 6.5 167 Base 0.35 200 200 130.0 70.0 27.0 105 121.0 112.8 7.8 168 Base 0.35 200 250 162.5 87.5 35.2 105 123.4 114.0 9.0 169 Base 0.35 200 150 97.5 52.5 18.9 110 118.6 114.1 4.1 170 Base 0.35 200 200 130.0 70.0 27.0 110 121.0 115.3 5.3 171 Base 0.35 200 250 162.5 87.5 35.2 110 123.4 116.6 6.6 172 Base 0.35 200 150 97.5 52.5 18.9 115 118.6 116.7 1.7 173 Base 0.35 200 200 130.0 70.0 27.0 115 121.0 117.9 2.9 174 Base 0.35 200 250 162.5 87.5 35.2 115 123.4 119.1 4.1 175 Base 0.35 200 150 97.5 52.5 18.9 120 118.6 119.3 -0.7 176 Base 0.35 200 200 130.0 70.0 27.0 120 121.0 120.5 0.5 177 Base 0.35 200 250 162.5 87.5 35.2 120 123.4 121.6 1.6 178 Base 0.35 200 150 97.5 52.5 18.9 125 118.6 122.0 -3.0



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 179 Base 0.35 200 200 130.0 70.0 27.0 125 121.0 123.1 -1.9 180 Base 0.35 200 250 162.5 87.5 35.2 125 123.4 124.2 -0.8 181 Entrainment Cutoff Wall 0.00 220 150 150.0 0.0 0.0 105 111.5 105.0 0.0 182 Entrainment Cutoff Wall 0.00 220 200 200.0 0.0 0.0 105 111.5 105.0 0.0 183 Entrainment Cutoff Wall 0.00 220 250 220.0 30.0 0.0 105 115.6 106.3 1.3 184 Entrainment Cutoff Wall 0.00 220 150 150.0 0.0 0.0 110 111.5 110.0 0.0 185 Entrainment Cutoff Wall 0.00 220 200 200.0 0.0 0.0 110 111.5 110.0 0.0 186 Entrainment Cutoff Wall 0.00 220 250 220.0 30.0 0.0 110 115.6 110.7 0.7 187 Entrainment Cutoff Wall 0.00 220 150 150.0 0.0 0.0 115 111.5 115.0 0.0 188 Entrainment Cutoff Wall 0.00 220 200 200.0 0.0 0.0 115 111.5 115.0 0.0 189 Entrainment Cutoff Wall 0.00 220 250 220.0 30.0 0.0 115 115.6 115.1 0.1 190 Entrainment Cutoff Wall 0.00 220 150 150.0 0.0 0.0 120 111.5 120.0 0.0 191 Entrainment Cutoff Wall 0.00 220 200 200.0 0.0 0.0 120 111.5 120.0 0.0 192 Entrainment Cutoff Wall 0.00 220 250 220.0 30.0 0.0 120 115.6 119.5 -0.5 193 Entrainment Cutoff Wall 0.00 220 150 150.0 0.0 0.0 125 111.5 125.0 0.0 194 Entrainment Cutoff Wall 0.00 220 200 200.0 0.0 0.0 125 111.5 125.0 0.0 195 Entrainment Cutoff Wall 0.00 220 250 220.0 30.0 0.0 125 115.6 123.9 -1.1 196 Entrainment Cutoff Wall 0.05 220 150 142.5 7.5 0.0 105 112.5 105.4 0.4 197 Entrainment Cutoff Wall 0.05 220 200 190.0 10.0 0.0 105 112.9 105.4 0.4 198 Entrainment Cutoff Wall 0.05 220 250 220.0 30.0 0.0 105 115.6 106.3 1.3 199 Entrainment Cutoff Wall 0.05 220 150 142.5 7.5 0.0 110 112.5 110.1 0.1 200 Entrainment Cutoff Wall 0.05 220 200 190.0 10.0 0.0 110 112.9 110.1 0.1 201 Entrainment Cutoff Wall 0.05 220 250 220.0 30.0 0.0 110 115.6 110.7 0.7 202 Entrainment Cutoff Wall 0.05 220 150 142.5 7.5 0.0 115 112.5 114.9 -0.1 203 Entrainment Cutoff Wall 0.05 220 200 190.0 10.0 0.0 115 112.9 114.9 -0.1 204 Entrainment Cutoff Wall 0.05 220 250 220.0 30.0 0.0 115 115.6 115.1 0.1



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 205 Entrainment Cutoff Wall 0.05 220 150 142.5 7.5 0.0 120 112.5 119.6 -0.4 206 Entrainment Cutoff Wall 0.05 220 200 190.0 10.0 0.0 120 112.9 119.6 -0.4 207 Entrainment Cutoff Wall 0.05 220 250 220.0 30.0 0.0 120 115.6 119.5 -0.5 208 Entrainment Cutoff Wall 0.05 220 150 142.5 7.5 0.0 125 112.5 124.4 -0.6 209 Entrainment Cutoff Wall 0.05 220 200 190.0 10.0 0.0 125 112.9 124.4 -0.6 210 Entrainment Cutoff Wall 0.05 220 250 220.0 30.0 0.0 125 115.6 123.9 -1.1 211 Entrainment Cutoff Wall 0.10 220 150 135.0 15.0 0.0 105 113.5 105.9 0.9 212 Entrainment Cutoff Wall 0.10 220 200 180.0 20.0 0.0 105 114.2 105.9 0.9 213 Entrainment Cutoff Wall 0.10 220 250 220.0 30.0 0.0 105 115.6 106.3 1.3 214 Entrainment Cutoff Wall 0.10 220 150 135.0 15.0 0.0 110 113.5 110.4 0.4 215 Entrainment Cutoff Wall 0.10 220 200 180.0 20.0 0.0 110 114.2 110.4 0.4 216 Entrainment Cutoff Wall 0.10 220 250 220.0 30.0 0.0 110 115.6 110.7 0.7 217 Entrainment Cutoff Wall 0.10 220 150 135.0 15.0 0.0 115 113.5 114.9 -0.1 218 Entrainment Cutoff Wall 0.10 220 200 180.0 20.0 0.0 115 114.2 114.9 -0.1 219 Entrainment Cutoff Wall 0.10 220 250 220.0 30.0 0.0 115 115.6 115.1 0.1 220 Entrainment Cutoff Wall 0.10 220 150 135.0 15.0 0.0 120 113.5 119.4 -0.6 221 Entrainment Cutoff Wall 0.10 220 200 180.0 20.0 0.0 120 114.2 119.4 -0.6 222 Entrainment Cutoff Wall 0.10 220 250 220.0 30.0 0.0 120 115.6 119.5 -0.5 223 Entrainment Cutoff Wall 0.10 220 150 135.0 15.0 0.0 125 113.5 123.9 -1.1 224 Entrainment Cutoff Wall 0.10 220 200 180.0 20.0 0.0 125 114.2 123.9 -1.1 225 Entrainment Cutoff Wall 0.10 220 250 220.0 30.0 0.0 125 115.6 123.9 -1.1 226 Entrainment Cutoff Wall 0.15 220 150 127.5 22.5 0.0 105 114.5 106.4 1.4 227 Entrainment Cutoff Wall 0.15 220 200 170.0 30.0 0.0 105 115.6 106.6 1.6 228 Entrainment Cutoff Wall 0.15 220 250 212.5 37.5 0.0 105 116.6 106.7 1.7 229 Entrainment Cutoff Wall 0.15 220 150 127.5 22.5 0.0 110 114.5 110.7 0.7 230 Entrainment Cutoff Wall 0.15 220 200 170.0 30.0 0.0 110 115.6 110.8 0.8



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 231 Entrainment Cutoff Wall 0.15 220 250 212.5 37.5 0.0 110 116.6 111.0 1.0 232 Entrainment Cutoff Wall 0.15 220 150 127.5 22.5 0.0 115 114.5 114.9 -0.1 233 Entrainment Cutoff Wall 0.15 220 200 170.0 30.0 0.0 115 115.6 115.1 0.1 234 Entrainment Cutoff Wall 0.15 220 250 212.5 37.5 0.0 115 116.6 115.2 0.2 235 Entrainment Cutoff Wall 0.15 220 150 127.5 22.5 0.0 120 114.5 119.2 -0.8 236 Entrainment Cutoff Wall 0.15 220 200 170.0 30.0 0.0 120 115.6 119.3 -0.7 237 Entrainment Cutoff Wall 0.15 220 250 212.5 37.5 0.0 120 116.6 119.5 -0.5 238 Entrainment Cutoff Wall 0.15 220 150 127.5 22.5 0.0 125 114.5 123.4 -1.6 239 Entrainment Cutoff Wall 0.15 220 200 170.0 30.0 0.0 125 115.6 123.6 -1.4 240 Entrainment Cutoff Wall 0.15 220 250 212.5 37.5 0.0 125 116.6 123.7 -1.3 241 Entrainment Cutoff Wall 0.25 220 150 112.5 37.5 0.0 105 116.6 107.9 2.9 242 Entrainment Cutoff Wall 0.25 220 200 150.0 50.0 0.0 105 118.3 108.3 3.3 243 Entrainment Cutoff Wall 0.25 220 250 187.5 62.5 0.0 105 120.0 108.7 3.7 244 Entrainment Cutoff Wall 0.25 220 150 112.5 37.5 0.0 110 116.6 111.6 1.6 245 Entrainment Cutoff Wall 0.25 220 200 150.0 50.0 0.0 110 118.3 112.1 2.1 246 Entrainment Cutoff Wall 0.25 220 250 187.5 62.5 0.0 110 120.0 112.5 2.5 247 Entrainment Cutoff Wall 0.25 220 150 112.5 37.5 0.0 115 116.6 115.4 0.4 248 Entrainment Cutoff Wall 0.25 220 200 150.0 50.0 0.0 115 118.3 115.8 0.8 249 Entrainment Cutoff Wall 0.25 220 250 187.5 62.5 0.0 115 120.0 116.2 1.2 250 Entrainment Cutoff Wall 0.25 220 150 112.5 37.5 0.0 120 116.6 119.1 -0.9 251 Entrainment Cutoff Wall 0.25 220 200 150.0 50.0 0.0 120 118.3 119.6 -0.4 252 Entrainment Cutoff Wall 0.25 220 250 187.5 62.5 0.0 120 120.0 120.0 0.0 253 Entrainment Cutoff Wall 0.25 220 150 112.5 37.5 0.0 125 116.6 122.9 -2.1 254 Entrainment Cutoff Wall 0.25 220 200 150.0 50.0 0.0 125 118.3 123.3 -1.7 255 Entrainment Cutoff Wall 0.25 220 250 187.5 62.5 0.0 125 120.0 123.7 -1.3 256 Entrainment Cutoff Wall 0.35 220 150 97.5 52.5 0.0 105 118.6 109.8 4.8



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 257 Entrainment Cutoff Wall 0.35 220 200 130.0 70.0 0.0 105 121.0 110.6 5.6 258 Entrainment Cutoff Wall 0.35 220 250 162.5 87.5 0.0 105 123.4 111.4 6.4 259 Entrainment Cutoff Wall 0.35 220 150 97.5 52.5 0.0 110 118.6 113.0 3.0 260 Entrainment Cutoff Wall 0.35 220 200 130.0 70.0 0.0 110 121.0 113.8 3.8 261 Entrainment Cutoff Wall 0.35 220 250 162.5 87.5 0.0 110 123.4 114.7 4.7 262 Entrainment Cutoff Wall 0.35 220 150 97.5 52.5 0.0 115 118.6 116.3 1.3 263 Entrainment Cutoff Wall 0.35 220 200 130.0 70.0 0.0 115 121.0 117.1 2.1 264 Entrainment Cutoff Wall 0.35 220 250 162.5 87.5 0.0 115 123.4 117.9 2.9 265 Entrainment Cutoff Wall 0.35 220 150 97.5 52.5 0.0 120 118.6 119.5 -0.5 266 Entrainment Cutoff Wall 0.35 220 200 130.0 70.0 0.0 120 121.0 120.3 0.3 267 Entrainment Cutoff Wall 0.35 220 250 162.5 87.5 0.0 120 123.4 121.2 1.2 268 Entrainment Cutoff Wall 0.35 220 150 97.5 52.5 0.0 125 118.6 122.8 -2.2 269 Entrainment Cutoff Wall 0.35 220 200 130.0 70.0 0.0 125 121.0 123.6 -1.4 270 Entrainment Cutoff Wall 0.35 220 250 162.5 87.5 0.0 125 123.4 124.4 -0.6 271 Entrainment Cutoff Wall 0.00 200 150 150.0 0.0 0.0 105 111.5 105.0 0.0 272 Entrainment Cutoff Wall 0.00 200 200 200.0 0.0 0.0 105 111.5 105.0 0.0 273 Entrainment Cutoff Wall 0.00 200 250 200.0 50.0 0.0 105 118.3 107.7 2.7 274 Entrainment Cutoff Wall 0.00 200 150 150.0 0.0 0.0 110 111.5 110.0 0.0 275 Entrainment Cutoff Wall 0.00 200 200 200.0 0.0 0.0 110 111.5 110.0 0.0 276 Entrainment Cutoff Wall 0.00 200 250 200.0 50.0 0.0 110 118.3 111.7 1.7 277 Entrainment Cutoff Wall 0.00 200 150 150.0 0.0 0.0 115 111.5 115.0 0.0 278 Entrainment Cutoff Wall 0.00 200 200 200.0 0.0 0.0 115 111.5 115.0 0.0 279 Entrainment Cutoff Wall 0.00 200 250 200.0 50.0 0.0 115 118.3 115.7 0.7 280 Entrainment Cutoff Wall 0.00 200 150 150.0 0.0 0.0 120 111.5 120.0 0.0 281 Entrainment Cutoff Wall 0.00 200 200 200.0 0.0 0.0 120 111.5 120.0 0.0 282 Entrainment Cutoff Wall 0.00 200 250 200.0 50.0 0.0 120 118.3 119.7 -0.3



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 283 Entrainment Cutoff Wall 0.00 200 150 150.0 0.0 0.0 125 111.5 125.0 0.0 284 Entrainment Cutoff Wall 0.00 200 200 200.0 0.0 0.0 125 111.5 125.0 0.0 285 Entrainment Cutoff Wall 0.00 200 250 200.0 50.0 0.0 125 118.3 123.7 -1.3 286 Entrainment Cutoff Wall 0.05 200 150 142.5 7.5 0.0 105 112.5 105.4 0.4 287 Entrainment Cutoff Wall 0.05 200 200 190.0 10.0 0.0 105 112.9 105.4 0.4 288 Entrainment Cutoff Wall 0.05 200 250 200.0 50.0 0.0 105 118.3 107.7 2.7 289 Entrainment Cutoff Wall 0.05 200 150 142.5 7.5 0.0 110 112.5 110.1 0.1 290 Entrainment Cutoff Wall 0.05 200 200 190.0 10.0 0.0 110 112.9 110.1 0.1 291 Entrainment Cutoff Wall 0.05 200 250 200.0 50.0 0.0 110 118.3 111.7 1.7 292 Entrainment Cutoff Wall 0.05 200 150 142.5 7.5 0.0 115 112.5 114.9 -0.1 293 Entrainment Cutoff Wall 0.05 200 200 190.0 10.0 0.0 115 112.9 114.9 -0.1 294 Entrainment Cutoff Wall 0.05 200 250 200.0 50.0 0.0 115 118.3 115.7 0.7 295 Entrainment Cutoff Wall 0.05 200 150 142.5 7.5 0.0 120 112.5 119.6 -0.4 296 Entrainment Cutoff Wall 0.05 200 200 190.0 10.0 0.0 120 112.9 119.6 -0.4 297 Entrainment Cutoff Wall 0.05 200 250 200.0 50.0 0.0 120 118.3 119.7 -0.3 298 Entrainment Cutoff Wall 0.05 200 150 142.5 7.5 0.0 125 112.5 124.4 -0.6 299 Entrainment Cutoff Wall 0.05 200 200 190.0 10.0 0.0 125 112.9 124.4 -0.6 300 Entrainment Cutoff Wall 0.05 200 250 200.0 50.0 0.0 125 118.3 123.7 -1.3 301 Entrainment Cutoff Wall 0.10 200 150 135.0 15.0 0.0 105 113.5 105.9 0.9 302 Entrainment Cutoff Wall 0.10 200 200 180.0 20.0 0.0 105 114.2 105.9 0.9 303 Entrainment Cutoff Wall 0.10 200 250 200.0 50.0 0.0 105 118.3 107.7 2.7 304 Entrainment Cutoff Wall 0.10 200 150 135.0 15.0 0.0 110 113.5 110.4 0.4 305 Entrainment Cutoff Wall 0.10 200 200 180.0 20.0 0.0 110 114.2 110.4 0.4 306 Entrainment Cutoff Wall 0.10 200 250 200.0 50.0 0.0 110 118.3 111.7 1.7 307 Entrainment Cutoff Wall 0.10 200 150 135.0 15.0 0.0 115 113.5 114.9 -0.1 308 Entrainment Cutoff Wall 0.10 200 200 180.0 20.0 0.0 115 114.2 114.9 -0.1



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 309 Entrainment Cutoff Wall 0.10 200 250 200.0 50.0 0.0 115 118.3 115.7 0.7 310 Entrainment Cutoff Wall 0.10 200 150 135.0 15.0 0.0 120 113.5 119.4 -0.6 311 Entrainment Cutoff Wall 0.10 200 200 180.0 20.0 0.0 120 114.2 119.4 -0.6 312 Entrainment Cutoff Wall 0.10 200 250 200.0 50.0 0.0 120 118.3 119.7 -0.3 313 Entrainment Cutoff Wall 0.10 200 150 135.0 15.0 0.0 125 113.5 123.9 -1.1 314 Entrainment Cutoff Wall 0.10 200 200 180.0 20.0 0.0 125 114.2 123.9 -1.1 315 Entrainment Cutoff Wall 0.10 200 250 200.0 50.0 0.0 125 118.3 123.7 -1.3 316 Entrainment Cutoff Wall 0.15 200 150 127.5 22.5 0.0 105 114.5 106.4 1.4 317 Entrainment Cutoff Wall 0.15 200 200 170.0 30.0 0.0 105 115.6 106.6 1.6 318 Entrainment Cutoff Wall 0.15 200 250 200.0 50.0 0.0 105 118.3 107.7 2.7 319 Entrainment Cutoff Wall 0.15 200 150 127.5 22.5 0.0 110 114.5 110.7 0.7 320 Entrainment Cutoff Wall 0.15 200 200 170.0 30.0 0.0 110 115.6 110.8 0.8 321 Entrainment Cutoff Wall 0.15 200 250 200.0 50.0 0.0 110 118.3 111.7 1.7 322 Entrainment Cutoff Wall 0.15 200 150 127.5 22.5 0.0 115 114.5 114.9 -0.1 323 Entrainment Cutoff Wall 0.15 200 200 170.0 30.0 0.0 115 115.6 115.1 0.1 324 Entrainment Cutoff Wall 0.15 200 250 200.0 50.0 0.0 115 118.3 115.7 0.7 325 Entrainment Cutoff Wall 0.15 200 150 127.5 22.5 0.0 120 114.5 119.2 -0.8 326 Entrainment Cutoff Wall 0.15 200 200 170.0 30.0 0.0 120 115.6 119.3 -0.7 327 Entrainment Cutoff Wall 0.15 200 250 200.0 50.0 0.0 120 118.3 119.7 -0.3 328 Entrainment Cutoff Wall 0.15 200 150 127.5 22.5 0.0 125 114.5 123.4 -1.6 329 Entrainment Cutoff Wall 0.15 200 200 170.0 30.0 0.0 125 115.6 123.6 -1.4 330 Entrainment Cutoff Wall 0.15 200 250 200.0 50.0 0.0 125 118.3 123.7 -1.3 331 Entrainment Cutoff Wall 0.25 200 150 112.5 37.5 0.0 105 116.6 107.9 2.9 332 Entrainment Cutoff Wall 0.25 200 200 150.0 50.0 0.0 105 118.3 108.3 3.3 333 Entrainment Cutoff Wall 0.25 200 250 187.5 62.5 0.0 105 120.0 108.7 3.7 334 Entrainment Cutoff Wall 0.25 200 150 112.5 37.5 0.0 110 116.6 111.6 1.6



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 335 Entrainment Cutoff Wall 0.25 200 200 150.0 50.0 0.0 110 118.3 112.1 2.1 336 Entrainment Cutoff Wall 0.25 200 250 187.5 62.5 0.0 110 120.0 112.5 2.5 337 Entrainment Cutoff Wall 0.25 200 150 112.5 37.5 0.0 115 116.6 115.4 0.4 338 Entrainment Cutoff Wall 0.25 200 200 150.0 50.0 0.0 115 118.3 115.8 0.8 339 Entrainment Cutoff Wall 0.25 200 250 187.5 62.5 0.0 115 120.0 116.2 1.2 340 Entrainment Cutoff Wall 0.25 200 150 112.5 37.5 0.0 120 116.6 119.1 -0.9 341 Entrainment Cutoff Wall 0.25 200 200 150.0 50.0 0.0 120 118.3 119.6 -0.4 342 Entrainment Cutoff Wall 0.25 200 250 187.5 62.5 0.0 120 120.0 120.0 0.0 343 Entrainment Cutoff Wall 0.25 200 150 112.5 37.5 0.0 125 116.6 122.9 -2.1 344 Entrainment Cutoff Wall 0.25 200 200 150.0 50.0 0.0 125 118.3 123.3 -1.7 345 Entrainment Cutoff Wall 0.25 200 250 187.5 62.5 0.0 125 120.0 123.7 -1.3 346 Entrainment Cutoff Wall 0.35 200 150 97.5 52.5 0.0 105 118.6 109.8 4.8 347 Entrainment Cutoff Wall 0.35 200 200 130.0 70.0 0.0 105 121.0 110.6 5.6 348 Entrainment Cutoff Wall 0.35 200 250 162.5 87.5 0.0 105 123.4 111.4 6.4 349 Entrainment Cutoff Wall 0.35 200 150 97.5 52.5 0.0 110 118.6 113.0 3.0 350 Entrainment Cutoff Wall 0.35 200 200 130.0 70.0 0.0 110 121.0 113.8 3.8 351 Entrainment Cutoff Wall 0.35 200 250 162.5 87.5 0.0 110 123.4 114.7 4.7 352 Entrainment Cutoff Wall 0.35 200 150 97.5 52.5 0.0 115 118.6 116.3 1.3 353 Entrainment Cutoff Wall 0.35 200 200 130.0 70.0 0.0 115 121.0 117.1 2.1 354 Entrainment Cutoff Wall 0.35 200 250 162.5 87.5 0.0 115 123.4 117.9 2.9 355 Entrainment Cutoff Wall 0.35 200 150 97.5 52.5 0.0 120 118.6 119.5 -0.5 356 Entrainment Cutoff Wall 0.35 200 200 130.0 70.0 0.0 120 121.0 120.3 0.3 357 Entrainment Cutoff Wall 0.35 200 250 162.5 87.5 0.0 120 123.4 121.2 1.2 358 Entrainment Cutoff Wall 0.35 200 150 97.5 52.5 0.0 125 118.6 122.8 -2.2 359 Entrainment Cutoff Wall 0.35 200 200 130.0 70.0 0.0 125 121.0 123.6 -1.4 360 Entrainment Cutoff Wall 0.35 200 250 162.5 87.5 0.0 125 123.4 124.4 -0.6



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 361 SD&RTW 0.00 220 150 150.0 0.0 0.0 105 105.0 105.0 0.0 362 SD&RTW 0.00 220 200 200.0 0.0 0.0 105 105.0 105.0 0.0 363 SD&RTW 0.00 220 250 220.0 30.0 30.0 105 114.1 107.2 2.2 364 SD&RTW 0.00 220 150 150.0 0.0 0.0 110 110.0 110.0 0.0 365 SD&RTW 0.00 220 200 200.0 0.0 0.0 110 110.0 110.0 0.0 366 SD&RTW 0.00 220 250 220.0 30.0 30.0 110 114.1 111.0 1.0 367 SD&RTW 0.00 220 150 150.0 0.0 0.0 115 115.0 115.0 0.0 368 SD&RTW 0.00 220 200 200.0 0.0 0.0 115 115.0 115.0 0.0 369 SD&RTW 0.00 220 250 220.0 30.0 30.0 115 114.1 114.8 -0.2 370 SD&RTW 0.00 220 150 150.0 0.0 0.0 120 120.0 120.0 0.0 371 SD&RTW 0.00 220 200 200.0 0.0 0.0 120 120.0 120.0 0.0 372 SD&RTW 0.00 220 250 220.0 30.0 30.0 120 114.1 118.6 -1.4 373 SD&RTW 0.00 220 150 150.0 0.0 0.0 125 125.0 125.0 0.0 374 SD&RTW 0.00 220 200 200.0 0.0 0.0 125 125.0 125.0 0.0 375 SD&RTW 0.00 220 250 220.0 30.0 30.0 125 114.1 122.4 -2.6 376 SD&RTW 0.05 220 150 142.5 7.5 7.5 105 112.4 105.7 0.7 377 SD&RTW 0.05 220 200 190.0 10.0 10.0 105 113.2 105.8 0.8 378 SD&RTW 0.05 220 250 220.0 30.0 30.0 105 114.1 107.2 2.2 379 SD&RTW 0.05 220 150 142.5 7.5 7.5 110 112.4 110.2 0.2 380 SD&RTW 0.05 220 200 190.0 10.0 10.0 110 113.2 110.3 0.3 381 SD&RTW 0.05 220 250 220.0 30.0 30.0 110 114.1 111.0 1.0 382 SD&RTW 0.05 220 150 142.5 7.5 7.5 115 112.4 114.7 -0.3 383 SD&RTW 0.05 220 200 190.0 10.0 10.0 115 113.2 114.8 -0.2 384 SD&RTW 0.05 220 250 220.0 30.0 30.0 115 114.1 114.8 -0.2 385 SD&RTW 0.05 220 150 142.5 7.5 7.5 120 112.4 119.2 -0.8 386 SD&RTW 0.05 220 200 190.0 10.0 10.0 120 113.2 119.3 -0.7



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 387 SD&RTW 0.05 220 250 220.0 30.0 30.0 120 114.1 118.6 -1.4 388 SD&RTW 0.05 220 150 142.5 7.5 7.5 125 112.4 123.7 -1.3 389 SD&RTW 0.05 220 200 190.0 10.0 10.0 125 113.2 123.8 -1.2 390 SD&RTW 0.05 220 250 220.0 30.0 30.0 125 114.1 122.4 -2.6 391 SD&RTW 0.10 220 150 135.0 15.0 15.0 105 112.4 106.5 1.5 392 SD&RTW 0.10 220 200 180.0 20.0 20.0 105 113.2 106.6 1.6 393 SD&RTW 0.10 220 250 220.0 30.0 30.0 105 114.1 107.2 2.2 394 SD&RTW 0.10 220 150 135.0 15.0 15.0 110 112.4 110.5 0.5 395 SD&RTW 0.10 220 200 180.0 20.0 20.0 110 113.2 110.6 0.6 396 SD&RTW 0.10 220 250 220.0 30.0 30.0 110 114.1 111.0 1.0 397 SD&RTW 0.10 220 150 135.0 15.0 15.0 115 112.4 114.5 -0.5 398 SD&RTW 0.10 220 200 180.0 20.0 20.0 115 113.2 114.6 -0.4 399 SD&RTW 0.10 220 250 220.0 30.0 30.0 115 114.1 114.8 -0.2 400 SD&RTW 0.10 220 150 135.0 15.0 15.0 120 112.4 118.5 -1.5 401 SD&RTW 0.10 220 200 180.0 20.0 20.0 120 113.2 118.6 -1.4 402 SD&RTW 0.10 220 250 220.0 30.0 30.0 120 114.1 118.6 -1.4 403 SD&RTW 0.10 220 150 135.0 15.0 15.0 125 112.4 122.5 -2.5 404 SD&RTW 0.10 220 200 180.0 20.0 20.0 125 113.2 122.6 -2.4 405 SD&RTW 0.10 220 250 220.0 30.0 30.0 125 114.1 122.4 -2.6 406 SD&RTW 0.15 220 150 127.5 22.5 22.5 105 112.4 107.2 2.2 407 SD&RTW 0.15 220 200 170.0 30.0 30.0 105 113.2 107.5 2.5 408 SD&RTW 0.15 220 250 212.5 37.5 37.5 105 114.1 107.7 2.7 409 SD&RTW 0.15 220 150 127.5 22.5 22.5 110 112.4 110.7 0.7 410 SD&RTW 0.15 220 200 170.0 30.0 30.0 110 113.2 111.0 1.0 411 SD&RTW 0.15 220 250 212.5 37.5 37.5 110 114.1 111.2 1.2 412 SD&RTW 0.15 220 150 127.5 22.5 22.5 115 112.4 114.2 -0.8



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 413 SD&RTW 0.15 220 200 170.0 30.0 30.0 115 113.2 114.5 -0.5 414 SD&RTW 0.15 220 250 212.5 37.5 37.5 115 114.1 114.7 -0.3 415 SD&RTW 0.15 220 150 127.5 22.5 22.5 120 112.4 117.7 -2.3 416 SD&RTW 0.15 220 200 170.0 30.0 30.0 120 113.2 118.0 -2.0 417 SD&RTW 0.15 220 250 212.5 37.5 37.5 120 114.1 118.2 -1.8 418 SD&RTW 0.15 220 150 127.5 22.5 22.5 125 112.4 121.2 -3.8 419 SD&RTW 0.15 220 200 170.0 30.0 30.0 125 113.2 121.5 -3.5 420 SD&RTW 0.15 220 250 212.5 37.5 37.5 125 114.1 121.7 -3.3 421 SD&RTW 0.25 220 150 112.5 37.5 22.7 105 112.4 108.0 3.0 422 SD&RTW 0.25 220 200 150.0 50.0 32.0 105 113.7 108.6 3.6 423 SD&RTW 0.25 220 250 187.5 62.5 41.4 105 116.0 109.6 4.6 424 SD&RTW 0.25 220 150 112.5 37.5 22.7 110 112.4 111.0 1.0 425 SD&RTW 0.25 220 200 150.0 50.0 32.0 110 113.7 111.5 1.5 426 SD&RTW 0.25 220 250 187.5 62.5 41.4 110 116.0 112.5 2.5 427 SD&RTW 0.25 220 150 112.5 37.5 22.7 115 112.4 114.0 -1.0 428 SD&RTW 0.25 220 200 150.0 50.0 32.0 115 113.7 114.5 -0.5 429 SD&RTW 0.25 220 250 187.5 62.5 41.4 115 116.0 115.4 0.4 430 SD&RTW 0.25 220 150 112.5 37.5 22.7 120 112.4 117.0 -3.0 431 SD&RTW 0.25 220 200 150.0 50.0 32.0 120 113.7 117.4 -2.6 432 SD&RTW 0.25 220 250 187.5 62.5 41.4 120 116.0 118.3 -1.7 433 SD&RTW 0.25 220 150 112.5 37.5 22.7 125 112.4 119.9 -5.1 434 SD&RTW 0.25 220 200 150.0 50.0 32.0 125 113.7 120.4 -4.6 435 SD&RTW 0.25 220 250 187.5 62.5 41.4 125 116.0 121.2 -3.8 436 SD&RTW 0.35 220 150 97.5 52.5 18.9 105 113.0 108.8 3.8 437 SD&RTW 0.35 220 200 130.0 70.0 27.0 105 115.4 110.1 5.1 438 SD&RTW 0.35 220 250 162.5 87.5 35.2 105 118.5 111.6 6.6



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 439 SD&RTW 0.35 220 150 97.5 52.5 18.9 110 113.0 111.4 1.4 440 SD&RTW 0.35 220 200 130.0 70.0 27.0 110 115.4 112.6 2.6 441 SD&RTW 0.35 220 250 162.5 87.5 35.2 110 118.5 114.2 4.2 442 SD&RTW 0.35 220 150 97.5 52.5 18.9 115 113.0 114.0 -1.0 443 SD&RTW 0.35 220 200 130.0 70.0 27.0 115 115.4 115.2 0.2 444 SD&RTW 0.35 220 250 162.5 87.5 35.2 115 118.5 116.7 1.7 445 SD&RTW 0.35 220 150 97.5 52.5 18.9 120 113.0 116.7 -3.3 446 SD&RTW 0.35 220 200 130.0 70.0 27.0 120 115.4 117.8 -2.2 447 SD&RTW 0.35 220 250 162.5 87.5 35.2 120 118.5 119.3 -0.7 448 SD&RTW 0.35 220 150 97.5 52.5 18.9 125 113.0 119.3 -5.7 449 SD&RTW 0.35 220 200 130.0 70.0 27.0 125 115.4 120.3 -4.7 450 SD&RTW 0.35 220 250 162.5 87.5 35.2 125 118.5 121.8 -3.2 451 SD&RTW 0.00 200 150 150.0 0.0 0.0 105 105.0 105.0 0.0 452 SD&RTW 0.00 200 200 200.0 0.0 0.0 105 105.0 105.0 0.0 453 SD&RTW 0.00 200 250 200.0 50.0 44.5 105 114.7 108.7 3.7 454 SD&RTW 0.00 200 150 150.0 0.0 0.0 110 110.0 110.0 0.0 455 SD&RTW 0.00 200 200 200.0 0.0 0.0 110 110.0 110.0 0.0 456 SD&RTW 0.00 200 250 200.0 50.0 44.5 110 114.7 111.8 1.8 457 SD&RTW 0.00 200 150 150.0 0.0 0.0 115 115.0 115.0 0.0 458 SD&RTW 0.00 200 200 200.0 0.0 0.0 115 115.0 115.0 0.0 459 SD&RTW 0.00 200 250 200.0 50.0 44.5 115 114.7 114.9 -0.1 460 SD&RTW 0.00 200 150 150.0 0.0 0.0 120 120.0 120.0 0.0 461 SD&RTW 0.00 200 200 200.0 0.0 0.0 120 120.0 120.0 0.0 462 SD&RTW 0.00 200 250 200.0 50.0 44.5 120 114.7 118.0 -2.0 463 SD&RTW 0.00 200 150 150.0 0.0 0.0 125 125.0 125.0 0.0 464 SD&RTW 0.00 200 200 200.0 0.0 0.0 125 125.0 125.0 0.0



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 465 SD&RTW 0.00 200 250 200.0 50.0 44.5 125 114.7 121.1 -3.9 466 SD&RTW 0.05 200 150 142.5 7.5 7.5 105 112.4 105.7 0.7 467 SD&RTW 0.05 200 200 190.0 10.0 10.0 105 113.2 105.8 0.8 468 SD&RTW 0.05 200 250 200.0 50.0 44.5 105 114.7 108.7 3.7 469 SD&RTW 0.05 200 150 142.5 7.5 7.5 110 112.4 110.2 0.2 470 SD&RTW 0.05 200 200 190.0 10.0 10.0 110 113.2 110.3 0.3 471 SD&RTW 0.05 200 250 200.0 50.0 44.5 110 114.7 111.8 1.8 472 SD&RTW 0.05 200 150 142.5 7.5 7.5 115 112.4 114.7 -0.3 473 SD&RTW 0.05 200 200 190.0 10.0 10.0 115 113.2 114.8 -0.2 474 SD&RTW 0.05 200 250 200.0 50.0 44.5 115 114.7 114.9 -0.1 475 SD&RTW 0.05 200 150 142.5 7.5 7.5 120 112.4 119.2 -0.8 476 SD&RTW 0.05 200 200 190.0 10.0 10.0 120 113.2 119.3 -0.7 477 SD&RTW 0.05 200 250 200.0 50.0 44.5 120 114.7 118.0 -2.0 478 SD&RTW 0.05 200 150 142.5 7.5 7.5 125 112.4 123.7 -1.3 479 SD&RTW 0.05 200 200 190.0 10.0 10.0 125 113.2 123.8 -1.2 480 SD&RTW 0.05 200 250 200.0 50.0 44.5 125 114.7 121.1 -3.9 481 SD&RTW 0.10 200 150 135.0 15.0 15.0 105 112.4 106.5 1.5 482 SD&RTW 0.10 200 200 180.0 20.0 20.0 105 113.2 106.6 1.6 483 SD&RTW 0.10 200 250 200.0 50.0 44.5 105 114.7 108.7 3.7 484 SD&RTW 0.10 200 150 135.0 15.0 15.0 110 112.4 110.5 0.5 485 SD&RTW 0.10 200 200 180.0 20.0 20.0 110 113.2 110.6 0.6 486 SD&RTW 0.10 200 250 200.0 50.0 44.5 110 114.7 111.8 1.8 487 SD&RTW 0.10 200 150 135.0 15.0 15.0 115 112.4 114.5 -0.5 488 SD&RTW 0.10 200 200 180.0 20.0 20.0 115 113.2 114.6 -0.4 489 SD&RTW 0.10 200 250 200.0 50.0 44.5 115 114.7 114.9 -0.1 490 SD&RTW 0.10 200 150 135.0 15.0 15.0 120 112.4 118.5 -1.5



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 491 SD&RTW 0.10 200 200 180.0 20.0 20.0 120 113.2 118.6 -1.4 492 SD&RTW 0.10 200 250 200.0 50.0 44.5 120 114.7 118.0 -2.0 493 SD&RTW 0.10 200 150 135.0 15.0 15.0 125 112.4 122.5 -2.5 494 SD&RTW 0.10 200 200 180.0 20.0 20.0 125 113.2 122.6 -2.4 495 SD&RTW 0.10 200 250 200.0 50.0 44.5 125 114.7 121.1 -3.9 496 SD&RTW 0.15 200 150 127.5 22.5 22.5 105 112.4 107.2 2.2 497 SD&RTW 0.15 200 200 170.0 30.0 30.0 105 113.2 107.5 2.5 498 SD&RTW 0.15 200 250 200.0 50.0 44.5 105 114.7 108.7 3.7 499 SD&RTW 0.15 200 150 127.5 22.5 22.5 110 112.4 110.7 0.7 500 SD&RTW 0.15 200 200 170.0 30.0 30.0 110 113.2 111.0 1.0 501 SD&RTW 0.15 200 250 200.0 50.0 44.5 110 114.7 111.8 1.8 502 SD&RTW 0.15 200 150 127.5 22.5 22.5 115 112.4 114.2 -0.8 503 SD&RTW 0.15 200 200 170.0 30.0 30.0 115 113.2 114.5 -0.5 504 SD&RTW 0.15 200 250 200.0 50.0 44.5 115 114.7 114.9 -0.1 505 SD&RTW 0.15 200 150 127.5 22.5 22.5 120 112.4 117.7 -2.3 506 SD&RTW 0.15 200 200 170.0 30.0 30.0 120 113.2 118.0 -2.0 507 SD&RTW 0.15 200 250 200.0 50.0 44.5 120 114.7 118.0 -2.0 508 SD&RTW 0.15 200 150 127.5 22.5 22.5 125 112.4 121.2 -3.8 509 SD&RTW 0.15 200 200 170.0 30.0 30.0 125 113.2 121.5 -3.5 510 SD&RTW 0.15 200 250 200.0 50.0 44.5 125 114.7 121.1 -3.9 511 SD&RTW 0.25 200 150 112.5 37.5 22.7 105 112.4 108.0 3.0 512 SD&RTW 0.25 200 200 150.0 50.0 32.0 105 113.7 108.6 3.6 513 SD&RTW 0.25 200 250 187.5 62.5 41.4 105 116.0 109.6 4.6 514 SD&RTW 0.25 200 150 112.5 37.5 22.7 110 112.4 111.0 1.0 515 SD&RTW 0.25 200 200 150.0 50.0 32.0 110 113.7 111.5 1.5 516 SD&RTW 0.25 200 250 187.5 62.5 41.4 110 116.0 112.5 2.5



Qph-max3

(kcfs) Qtotal

4

(kcfs) Qph

5

(kcfs) Qsp

6

(kcfs) Qent

7

(kcfs) TDGfb

8

(%) TDGsp

9

(%) TDGavg

10

(%) TDG-change11

(%) 517 SD&RTW 0.25 200 150 112.5 37.5 22.7 115 112.4 114.0 -1.0 518 SD&RTW 0.25 200 200 150.0 50.0 32.0 115 113.7 114.5 -0.5 519 SD&RTW 0.25 200 250 187.5 62.5 41.4 115 116.0 115.4 0.4 520 SD&RTW 0.25 200 150 112.5 37.5 22.7 120 112.4 117.0 -3.0 521 SD&RTW 0.25 200 200 150.0 50.0 32.0 120 113.7 117.4 -2.6 522 SD&RTW 0.25 200 250 187.5 62.5 41.4 120 116.0 118.3 -1.7 523 SD&RTW 0.25 200 150 112.5 37.5 22.7 125 112.4 119.9 -5.1 524 SD&RTW 0.25 200 200 150.0 50.0 32.0 125 113.7 120.4 -4.6 525 SD&RTW 0.25 200 250 187.5 62.5 41.4 125 116.0 121.2 -3.8 526 SD&RTW 0.35 200 150 97.5 52.5 18.9 105 113.0 108.8 3.8 527 SD&RTW 0.35 200 200 130.0 70.0 27.0 105 115.4 110.1 5.1 528 SD&RTW 0.35 200 250 162.5 87.5 35.2 105 118.5 111.6 6.6 529 SD&RTW 0.35 200 150 97.5 52.5 18.9 110 113.0 111.4 1.4 530 SD&RTW 0.35 200 200 130.0 70.0 27.0 110 115.4 112.6 2.6 531 SD&RTW 0.35 200 250 162.5 87.5 35.2 110 118.5 114.2 4.2 532 SD&RTW 0.35 200 150 97.5 52.5 18.9 115 113.0 114.0 -1.0 533 SD&RTW 0.35 200 200 130.0 70.0 27.0 115 115.4 115.2 0.2 534 SD&RTW 0.35 200 250 162.5 87.5 35.2 115 118.5 116.7 1.7 535 SD&RTW 0.35 200 150 97.5 52.5 18.9 120 113.0 116.7 -3.3 536 SD&RTW 0.35 200 200 130.0 70.0 27.0 120 115.4 117.8 -2.2 537 SD&RTW 0.35 200 250 162.5 87.5 35.2 120 118.5 119.3 -0.7 538 SD&RTW 0.35 200 150 97.5 52.5 18.9 125 113.0 119.3 -5.7 539 SD&RTW 0.35 200 200 130.0 70.0 27.0 125 115.4 120.3 -4.7 540 SD&RTW 0.35 200 250 162.5 87.5 35.2 125 118.5 121.8 -3.2

1 Base-Structural configuration as of 2004, Entrainment Cutoff Wall- EC Wall, spillway deflectors with raised tailwater channel (SD&RTW). 2 Spill policy fraction of river spilled subject to powerhouse capacity

3 Powerhouse flow capacity 4 Total river flow. 5 Powerhouse flow 6 Spillway flow at standard spill pattern 7 Powerhouse flow entrained into aerated spillway release 8 Total dissolved gas saturation in the forebay 9 Total dissolved gas saturation in spillway flow 10 Flow weighted total dissolved gas saturation 11 Total dissolved gas saturation change from forebay (TDGavg-TDGfb)

Documents

Rocky Reach Dam: Operational and Structural Total ... · Rocky Reach Dam: Operational and Structural Total Dissolved Gas Management by Michael L. Schneider and Steven C. Wilhelms