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Enhanced Canal Recharge
Feasibility Report
Yolo County Flood Control and Water Conservation District
Woodland, California USA
December 2012
This report is part of an AB303 grant funded project from the Local Groundwater Assistance program of the California Department of Water Resources. This report is a combined report including both Enhanced Canal Recharge and Gravel Pit Recharge tasks. Cooperation and access to the Capay Mining Facility was kindly provided by Granite Construction, Inc.
34274 State Highway 16, Woodland, CA 95695 530-662-0265 www.ycfcwcd.org
1
Table of Contents
Introduction ............................................................................................................................. 1
Background Information: Inflatable Dam on Cache Creek at Capay ............................ 3
Map of soil infiltration rates by canal reach ...................................................................... 3
Canal Infiltration Rates in Ponded Sections (Percolation Tests) .................................... 4
Percolation Tests: Field Data Acquisition Methods ...................................................... 7
Percolation Tests: Results ................................................................................................ 8
Potential for Increased Groundwater Storage ................................................................... 9
Promising Canal Stretches for Recharge ......................................................................... 11
Wintertime Canal Recharge Feasibility: Administrative Costs and Other Factors .... 11
Gravel Pit Recharge ............................................................................................................. 12
Aggregate Industry Partnerships ....................................................................................... 13
Infiltration Rate Estimates from Canal Flow Measurement: Data Acquisition ...... 13
Infiltration Rate Estimates from Canal Flow Measurement: Results ...................... 14
Gravel Pit Water Level and nearby Groundwater Levels: Data Acquisition ............ 15
Gravel Pit Water Level and nearby Groundwater Levels: Results ............................ 20
Conclusions ........................................................................................................................... 22
Recommended Action Plan ............................................................................................... 22
Introduction
During the original construction of the District’s canal system in 1914, it was known
that some canal reaches were very “leak prone” and that other areas lost less to
groundwater. At the time, a few of the leaky canal stretches were lined with
concrete, but 95% of the canals were left as dirt lined. Presumably, only a portion of
the canal was lined to save money, as lining canals is very expensive. However,
today it is the policy of the District to leave the canals unlined, to promote
groundwater recharge during the irrigation season (summer).
“Losses from this system, as seepage and evaporation, vary from year to
year, but have ranged from 15 to 65 percent from 1970 to 1996... The
greatest part of the losses is the result of seepage and percolation along the
canals and laterals. It is important to note, however, that the major part of
these losses are recoverable from the groundwater basin. Over the years,
various parties have suggested that the District should concrete-line its water
2
delivery system to minimize seepage losses. From the standpoint of
managing the water supply available from the Cache Creek system, lining
the District's water delivery system is not deemed to be a prudent water
management measure.” (YCFCWCD Water Management Plan 2000
http://archive.org/details/watermanagementp00borcrich)
In between winter storms, the canals are dry. If during these dry times in winter,
water could be diverted from Cache Creek into the canals, increased recharge could
be realized.
For this study, infiltration of canal recharge water was measured or summarized
using the following methods:
1. Delivery amount by volume minus sales and spills. The difference is gain
to groundwater.
2. Instantaneous flow rate measurement upstream and downstream of two
points. The difference is gain to groundwater.
3. Percolation tests. Water was ponded in more than 6,600 linear feet of
canal. The rate of drop in water level can be converted to a volumetric
infiltration rate.
All three methods compared well showing similar results (as explained in the
section on Percolation Test Results).
A map was also made showing SURRGO Soil Survey infiltration rates on all reaches
of the canal system. Historical recharge rates and measurements were also
summarized and compared to current findings. Infiltration measurements in
sections of canal were scaled up to the entire canal system. (Of note, there exists
infiltration data from 1914 in the District Archives.)
In addition to groundwater recharge from the bottom of unlined canals, winter
water can be applied to land areas, such as gravel pits, to promote recharge.
Delivering winter water for groundwater recharge to a nearby gravel pit near the
town of Capay, CA, was planned. However, this task was modified. Instead of
delivering water to the gravel pit, losses from a stretch of canal near the pit were
very closely measured. The losses from the canal entered the pit through an
3
underground path. Water levels in the canal, the pond in the pit, and nearby
monitoring wells were measured. The responsiveness of the pond to water losses in
the canal was analyzed. The gravel pit near Capay was unexpectedly found to have
a low infiltration rate, as explained in the Gravel Pit Results section.
Background Information: Inflatable Dam on Cache Creek at
Capay
In 1994, a 500 foot long inflatable bladder was installed on the top of Capay Dam.
This dam raises the water level 5 feet during the irrigation season. Previously,
wooden boards had to be installed at the beginning of each summer, taking 9
workers two days to accomplish. The process was repeated to remove the boards
each fall. Today, the bladder can be raised or lowered in 20 minutes at the touch of
a button. The bladder can also be operated remotely during storms and safely
observed w/ video camera surveillance.
The bladder was installed for safety reasons, but the District also wanted to have
the ability to inflate the dam in winter or early spring, when water is still flowing in
the Creek. Inflating the bladder in the winter allows the diversion of water in to the
canals for recharge purposes. This operation of the dam could facilitate
implementing the District's proposed groundwater recharge / recovery projects in
the canal system.
Map of soil infiltration rates by canal reach
Soil map data from Soil Survey Geographic (SSURGO) Database from the NRCS,
showing infiltration rate of the upper horizon layer of soil, was overlaid on the canal
system. SSURGO data presents a high and low infiltration rate for each soil horizon
and the low infiltration rate was used for the map. The lowest rate should be the
limiting rate for overall infiltration rate and therefore this low rate was used. A new
map, titled Soil Permeability, was created showing the infiltration rate along all
sections of the canal. The Soil Permeability map is attached.
SSURGO: Natural Resources Conservation Service, United States Department of
Agriculture. Soil Survey Geographic (SSURGO). Available online at
http://soildatamart.nrcs.usda.gov. Accessed June 2010.
4
Table 1. below shows a summary of canal lengths by infiltration rate as shown in
the attached Soil Permeability map. The majority of the canals have an infiltration
rate of 0.57 in/hr or less, while only 4 percent of the canals have an infiltration rate
of 1.98 in/hr or higher.
Table 1. Summary of canal length by infiltration rate as presented in
the attached Soil Permeability Map.
Infiltration Rate Canal Length Percent Infiltration
in/hr ksat Miles Length Category
0 0.0 0.08% Low
0.06 45.3 27% Low
0.2 51.2 31% Low
0.57 64.5 39% Med
1.98 2.6 2% High
5.95 3.1 2% High
total 166.9 total miles
The Soil Permeability map was used to plan and identify good areas for
measurement of ponded infiltration rate: high, medium, and low flow rates. The
map can also be used to identify promising sections of canal for future recharge
projects. Areas of higher recharge, in red and orange, are more promising than
green areas, with lower infiltration rates. Short sections of red canal areas near the
Capay Dam historically have been lined with concrete and are not available for
recharge activities today.
The map was also used to scale up the pond tests on each canal section (low, med,
high) to the infiltration rate of the entire District. The percent of high, medium, and
low infiltration rate areas was calculated from the map, and the results of the high,
medium, and low pond test were used to multiply up to the entire District canal
system. The results are presented in the Canal Infiltration section.
Canal Infiltration Rates in Ponded Sections (Percolation Tests)
At the end of the 2010 irrigation a large construction repair project necessitated
ending the irrigation season early, Sept 15, 2010. Usually the season ends as
irrigation demand tapers off, but with the quick drawdown in the canals, we were
able to “pond up” sections of the canal and block all inflow and outflow to these
5
sections. With our SCADA flow monitoring system, the drop in water level was
automatically measured and logged by the data collection system. In this way,
static pond infiltration rates were measured on more the 6,600 feet of canal.
Twenty-two canal sites were evaluated for possible inclusion in the ponding tests
(Table 2). Fourteen sites were eliminated right away, as they were located in
sloughs, did not have a downstream check to pond water, or were concrete lined
and were likely to have a very low infiltration rate. The remaining 8 sites were
considered in depth. One major concern was the ability to stop all incoming water
into the ponding area during the test. This meant that any remaining water draining
out of the canal system, and any drain water from nearby fields, had to be diverted
out of the ponding area. Only 4 sites were able to be configured this way; West
Adams @ Granite, the Chapman Reservoir Inlet, the Yolo Central Spill, and the
Winters Canal @ the Fredericks Flume. The Fredericks Flume site was tested, but no
data was collected. The steepness of the canal and the position of the water level
sensor was too far upstream of the check, so no water was beneath the sensor
during the test and no measurements could be made.
The remaining three sites were successfully measured during the pond test. These
sites are listed in bold in Table 2.
6
Table 2. Twenty two canal sites were evaluated for the end of season percolation test. The three sites highlighted in bold
were selected.
Canal Monitoring Site Operational? Site Notes
Possible
Infiltration
site
Upstream
Check
Downstream
Check Measured?
Clover Spill X earthen lined x CLV 0543 CLV 0601 No
PLP Spill #1 x earthen lined x PLP 0965 PLP 1013 No
PLP @ Gayle Check broken earthen lined x PLP 0534 PLP 0593 No
West Adams Canal @ Granite x earthen lined x WEA 0170 WEA 0240 Sept. 18, 2010
Alder Canal @ Gordon Slough Heading x earthen lined x WEA 0970 ALD 0009 No
Winters Canal @ Fredricks x earthen lined x WIN 1119 WIN 1313 attempted
Chapman Inlet x earthen lined x WIN 1536 WIN 1603 Sept. 14-15, 2010
Yolo Central Spill x earthen lined x YOC 0970 YOC 1008 Sept. 28-29, 2010
Alder Drop x concrete lined
Chapman Outlet x concrete lined
Cottonwood Spill x in slough
Fairfield Ditch Heading no sensors earthen lined
Gordon Slough Heading x in slough
Hungry Hollow Spill x in slough
PLP Spill #2 x concrete lined
Salisbury Spill x in slough
University Spill x concrete lined
West Adams Canal Heading x concrete lined
Willow Slough @ 98 x in slough
Willow Slough Bypass x in slough
Winters Canal Heading x concrete lined
Yolo Central Heading x no d/s check
7
Percolation Tests: Field Data Acquisition Methods
Water depth in the canals is measured constantly with a network of telemeterized
non-contact ultrasonic sensors. These data are logged on a server at District HQ
running the ClearSCADA database. A duplicate “hot standby” server is
simultaneously running at a remote location to ensure no lost data. The main use of
this system is to monitor canal flows and to manage irrigation deliveries. For the
pond infiltration test, this system was used to monitor dropping water levels in
sections of ponded canal. Canals were visually monitored periodically during the
test to check for leaks or water entering to ensure that changes in water level were
due to losses to groundwater only (evaporation over the few hours of the test were
estimated and found to be very small and were ignored).
Hydrographs showing the water level were printed out and the slope of the line
during the ponding test was measured and converted to infiltration in inches/hour.
Table 3 shows the date and duration of the ponding test for each location.
Table 3. Dates and time of ponding tests in three sections of canal during
September 2011
Canal section name Date of Pond Test Length of time used for level
drop measurement (hours)
WEA @ Granite 9-18-2010 8
WIN Chapman inlet 9-14-2010 12
YOC Spill 9-29-2010 15
8
After the canals dried out, the canal cross section dimensions were measured with
a tag line stretched across the canal and a measuring tape was used to measure
canal depth at each station along the tag line. The beginning and end of each
ponded canal section was measured and a minimum of 5 intermediate cross
sections were used to model the geometry and volume of the canal. Figure 1 shows
how the top one inch of water surface in the canal can be modeled as long thin
slab, or volume, of water. The upstream depth of water eventually reaches zero, as
the canal drops over its length while the water surface stays level (Figure 1).
Figure 1. The top surface of the ponded canal water was modeled as a one inch
thick rectangular volume of water (blue line).
Percolation Tests: Results
Table 4 shows the results of the percolation test in inches/hour. The results are
compared to SSURGO database values. The infiltration rates are also converted to
losses in CFS/mile and acre feet/day mile. These loss data can be used to “scale
up” and estimate losses for the entire District canal system (Table 4).
Ponded canal versus full flow infiltration rate is presented in Figure 1. The water
surface during the pond test was level, while the canal floor drops along its length
(Figure 1.) Therefore, the dimension of the modeled “thin slab of water” is a
9
different size at the ponded water surface, versus a full flowing canal. The
difference in these dimension are reflected in “ponded” versus “full flow” volumes in
Table 4.
Table 4. Results of ponding tests in three sections of canal during September 2010 Canal
section
name
Length
of
section
(ft)
Average
width full
flow (ft)
Volume of
top one
inch
ponded (cf)
Volume
of top
one inch
full flow
(cf)
Ksat
inches/hr
Measured
Ksat
inches/hr
SSURGO
cfs/
mile
acre
feet
/
day
mile
WEA @
Granite
1,440 30.6 3,336 3,675 0.50 .32 - 20 1.87 3.7
WIN
Chapman
inlet
3,552 18.66 5,523 5,523 0.29 .12 - 1.2 0.66 1.3
YOC Spill 1,640 12 1,367 1,640 0.25 .12 - .50 0.31 0.62
Note: Ksat from SSURGO does not match the Soil Infiltration map exactly because the map used low
values from the uppermost soil horizon, where depth is variable depending on location, and this
table uses the low value for the top 20 cm of the soil profile, regardless of the depth to the first
horizon.
Potential for Increased Groundwater Storage
The farms and cities within the District depend on the groundwater recharge that
occurs because of the unlined canals. The amount of recharge has been quantified
over the years and is presented Figure 2. The additional amount of recharge
available from winter water diversion (Table 5) into the canals will be compared to
the current amount of recharge that occurs.
10
Figure 2. YCFCWCD Annual losses to recharge. These losses are calculated as the
total releases from storage, minus the sales. The result is losses and the total is
assumed to be losses to groundwater, although small amount of evaporation and
spill occur. In 1977 and 1990 there were no deliveries of irrigation water and hence zero losses.
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
year
rech
arg
e w
ate
r (a
f)
The water lost from the canal system is mostly recoverable from the groundwater.
Figure 2 shows the amount lost to range from ~18,000 af in 2009 to a maximum of
~64,000 af in 1989 and on average 38,264 af of water is lost. Other data, for
example, Table 3 of the 2000 Water Management Plan
(http://www.archive.org/download/watermanagementp00borcrich/watermanage
mentp00borcrich.pdf), show that on average 28,500 af are lost to recharge each
year from the District’s system.
Table 5. Recharge estimates using pond test infiltration data
Category Canal
length
(mi)
af/day
mile
af/
day days af
Large Main Canal Winters Canal 16.05 1.3 21 212 4,423
Medium Main Canal West Adams Canal 10.55 3.7 39 212 8,275
Small Lateral Canal Laterals (using YOC Spill as average loss rate) 140.3 0.62 87 212 18,441
Total 166.9 31,140
11
In Table 5, estimates of losses from the pond infiltration tests were multiplied by
total length of the canal and an assumed 212 day season. Two hundred and twelve
days is the average season length between 1981 and 2009 (with minimum length
of 171 and maximum of 280 days). This analysis of pond infiltration data shows
that 31,140 af would be lost in an average length season. This amount is in
between the two estimates of losses from sales data discussed above (Figure 2).
Promising Canal Stretches for Recharge
There are two main canals in the District’s system: the Winters Canal, which diverts
water south of Cache Creek at Capay, and the West Adams which diverts waters on
the north and opposite side of the Creek. All other canals in the system branch off
of one of these two main canals (the Soil Permeability map, attached, shows the
canal system).
Any winter time diversions into the canal system will, by design, pass first into the
Winters or West Adams Canals.
The volume of recharge water depends on both the infiltration rate and the size of
the canal. Two stretches of canal can have a similar infiltration rate, for example
canal sections ‘WIN Chapman inlet’ and “YOC Spill’ from Table 3, but very different
recharge rates due to differences in overall size of the canal.
In most stretches of canal, the infiltration rate is relatively low. But because there
are so many miles of canal (166.9) the total infiltration rate for the system can be
significant. In other words, there are no particularly promising sections of canal,
most of the system must be used to achieve significant amounts of recharge.
Wintertime Canal Recharge Feasibility: Administrative Costs
and Other Factors
The main factor limiting wintertime recharge is that the canal system has dual
modes: summer-mode and winter-mode. During summer-mode the canals are full
for irrigation deliveries. During winter-mode the canals are empty to accept storm
runoff. Changing the canal configuration from summer-mode (irrigation) to winter-
12
mode typically requires a crew of 10 people to work one week. If a storm comes in
the winter and the canal system is in summer-mode (full of water for recharge), the
canals could overtop and flooding and damage could result.
For wintertime recharge the canals must be in summer-mode. However, since
storms cannot be predicted more than a few days in advance, when storms are
predicted, there is not enough time to switch from summer to winter mode.
Therefore the canals must remain in the wintertime configuration for the duration of
the winter season and recharge water cannot be introduced into the canals.
It is possible to install a system of automated gates, which would allow the canals
to switch from winter to summer mode in minutes, instead of days, allowing
wintertime recharge to occur. Although these gates could preserve the ability of the
canals to carry flood flows at a moments notice, it would take many years to plan,
finance, and install this system.
Even with an automated gate system, the system must be managed in such a way
to monitor for approaching storms, protect against localized flooding, and protect
the headgates and diversion works at Capay from flood damage. There will be an
incremental increase in administrative costs for these activities. Additionally, the
financing of a capital improvement program to install automated gates will incur
additional administrative overhead.
Gravel Pit Recharge
The use of existing gravel pits for active groundwater recharge has been discussed
for many years in Yolo County (YCFCWCD Water Management Plan 2000). Active
recharge allows the opportunity to increase groundwater storage and optimize
conjunctive use of both surface and groundwater resources. Optimized conjunctive
use can provide more water for all uses, without creating new surface water
reservoirs.
In 2006, the Yolo County Flood Control and Water Conservation District (the District)
completed a Countywide groundwater simulation model, which specifically looked
at using gravel pits in a groundwater recharge and recovery scenario.
For this current grant project, we planned to deliver water to the pit at Capay for
active recharge. However, no wintertime deliveries of water were made. Certain
13
aspects of the District’s irrigation system made it difficult or impossible to deliver
the water during winter. Infrastructure improvements of more than $25,000 were
needed to deliver the water, but were not part of the original budget. Additionally,
the road to the canal heading is dirt and not passable at times during wet winter
weather and the control gates could not be reached. After the end of the study, the
District installed remote control on these gates, but this feature was not available at
the time for the gravel pit test.
The gravel pit at the Granite Capay Facility is a 10 acre excavation in the ground, left
over from extraction of aggregate resources (gravel) (see Map 1).
Aggregate Industry Partnerships
Both aggregate mining and the District (or predecessor water companies) have a
long history in Yolo County, starting with the first white settlements in the 1850’s.
The aggregate industry along Cache Creek has been mining for high quality
aggregate resources since the late 1800’s. (Irrigation diversions started in 1856 at
the Moore Dam, with a water right currently held by the District.) Historically, gravel
mining was generally in the main Creek channel itself, but off-stream mining is
documented starting around 1981.
For the current study, Granite Construction kindly agreed to provide access to their
mining facility near Capay, CA, the pond, monitoring wells, and other monitoring
data in exchange for a copy of this report, when completed.
Infiltration Rate near the Gravel Pit from Canal Flow
Measurement: Field Data Acquisition
During normal canal operations, losses to groundwater must be taken into account.
For example, if a canal has sales for a particular day of 75 cfs, 100 cfs of water
must be delivered to the canal heading, to account for losses. By carefully
measuring flows upstream and downstream of a particular point along the canal,
losses can be quantified.
14
From April 30, 2012 to June 17, 2010, canal flows were manually measured daily
at 6 locations in the West Adams Canal system near the Granite Capay aggregate
mining facility (Figure 3). The weir stick overpour method was used
(http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/). The flows after June 17,
2010 became too high for use of the weir stick method and those measurements
were stopped. Two sites, the uppermost WEA0170 and the lowermost WEA0240
were equipped with continuous flow measurement sensors and telemetry allowing
real-time collection of flow data at these two sites (Figure 4). Figure 4 is a screen
shot from the District’s Real-time SCADA system. For each day shown in Figure 4, a
single value for daily average difference in flow was estimated and used to make
the hydrograph shown in Figure 5. Figure 5 shows the losses in cfs between the two
sites.
Infiltration Rate Estimates from Canal Flow Measurement:
Results
Shown in Figure 3 are the acre feet of water lost per day in the West Adams canal,
during the early irrigation season, from late April until mid May of 2010.
Approximately 20 acre feet were lost per day along that 1.81 mile section of canal
(WEA0170 to WEA0351CK), or 5.5 cfs per mile.
Figures 4 and 5 shows the losses from the canal nearby the Granite gravel mining
facility, between the WEA0170 and the WEA0240, a distance of 0.7 miles. The
water that was leaving the canal due to infiltration was moving into the ground and
percolating to the groundwater surface, “filling the profile” and raising the
groundwater. The daily average losses from the data in Figure 5 are 9.4 cfs, or 13.4
cfs/mile.
The difference in losses to groundwater between Figures 3 and 5 do not match
because the measurements involved different sections of canal.
15
Gravel Pit Water Level and nearby Groundwater Levels: Field
Data Acquisition
The monitoring wells surrounding the pit were surveyed during installation by
Granite Construction Inc an unknown number of years ago and this well casing
elevation data was supplied to District. For this current study, a GPS Total Station
survey instrument, with sub centimeter accuracy, was used to tie the canal water
and pond water levels in with the monitoring well casing elevations. A U-10 Hobo
waterlevel data logger was deployed in each of the wells and the pond, while the
previously constructed SCADA station at WEA0240 measured the water levels in
the canal. Water level monitoring locations are summarized in Table 6 and shown
on Map 1.
Table 6. recharge amounts using current infiltration data
Location name Reference Elevation
ft msl (NGV27)
UTM
10 S
Easting
UTM
Northing Notes
MW1 204.02 582888.54 4285410.24 Monitoring Well #1 (MW1)
MW2 198.29 583698.40 4285985.65 Monitoring Well #2 (MW2)
MW3 194.22 583963.88 4285390.20 Monitoring Well #3 (MW3)
Pond 1A Pond surface variable
-- --
Pond size and surface elevation is variable, for location please see Map #1
WEA0240CK 201.715 583033.94 4285899.23 West Adams Canal 0240 Check
16
Figure 3. Daily flow at 6 locations on the West Adams Canal near the Granite Capay facility. The difference in flow between
the uppermost location (WEA0170) and the most downstream location (WEA0351CK) is converted to af/day.
0
20
40
60
80
100
120
140
160
180
4/30
/201
0
5/1/
2010
5/2/
2010
5/3/
2010
5/4/
2010
5/5/
2010
5/6/
2010
5/7/
2010
5/8/
2010
5/9/
2010
5/10
/201
0
5/11
/201
0
5/12
/201
0
5/13
/201
0
5/14
/201
0
5/15
/201
0
5/16
/201
0
5/17
/201
0
Date
cfs
(o
r a
f/d
ay
)
WEA0170
WEA0180CK
WEA0240
WEA0267CK
WEA0315CK
WEA0351CK
af/day lost
17
Figure 4. Screenshot showing upstream and downstream flows at two locations. The difference in flow between the green
(upstream) and blue (downstream) lines is loss to groundwater.
18
Figure 5. Losses to groundwater as measured by difference in flow between two SCADA stations. Manual overpours from
STORM are measurements taken with the weir stick method.
Losses between WEA170 and 240
0
2
4
6
8
10
12
14
16
5/11
/2010
5/18
/2010
5/25
/2010
6/1/
2010
6/8/
2010
6/15
/2010
6/22
/2010
6/29
/2010
7/6/
2010
7/13
/2010
Date
cfs
SCADA
manual overpours from STORM
19
20
Gravel Pit Water Level and nearby Groundwater Levels: Results
Figure 6 shows the response of groundwater level and the pond surface level to rain
and irrigation water present in the canal. The water level in the pond rose 10 feet
when irrigation water was placed in the canal at the beginning of May, 2010 (Figure
6.) The closest monitoring well to the canal (MW2) rose more than 30 feet. At the
end of the irrigation season in September 2010, the groundwater level in MW2
immediately dropped, while the pond dropped very slowly.
The phase 1A pond at the Granite Capay Facility is 10 acres in size. A rise of 10 feet
in water level is 100 acrefeet (af). One hundred af is a very small amount of water
for the District which delivers over 180,000 af per year. Although the pond looks
like a surface water reservoir, it would be very small if so and not much use to the
District if it only held 100 af. It is better to think of the pond as a very large diameter
well. The water level in the pond reflects the water level in the surrounding aquifer.
The water levels for the pond in Figure 6 show that during irrigation season, the
pond is intermediate between the canal and MW2, up gradient, and MW3, down
gradient. It is apparent that the pond is filling with water from the canal.
During the non-irrigation season, the pond water level stays higher than the
surrounding aquifer, as shown in the monitoring wells. If there was a good hydraulic
connection between the bottom of the pond and the surrounding aquifer, the pond
should quickly drain. This does not appear to happen.
The pond is used at the Granite facility to dispose of ‘fines’ from the gravel washing
process. Perhaps the bottom of pond is clogging up with silt. The sides of the pit,
above the pond high water level, may not be clogged with silt and high groundwater
from the surrounding aquifer can drain into the pond, filling it. However, when the
surrounding groundwater levels drop below the level of the pond, the pond drains
very slowly. For the 24 days after the end of irrigation season, when no water was
present in the canal, the pond level dropped only 6.2 inches, a rate of 0.01 inches
per hour. This rate is more than 10 times smaller than any infiltration rate
measured in the canals (Table 4). Of note, the water level is MW1 was still high after
the end of irrigation season and water could be coming from up gradient to keep
the pond high, perhaps lowering the measured infiltration rate.
21
Figure 6. Water levels (NGV27) at the Granite Capay Facility during 2010. Rain also shown in vertical bars.
begin
irrig.
end
irrig.
22
Gravel Pit Conclusions
It appears that using the gravel pit pond as a recharge basin would not be very
effective, as it drains slowly in its current configuration. If the pond were filled with
water, it would remain relatively static and not recharge the aquifer. These are
preliminary results. Perhaps if the pond was filled with water above its current level
and no fines were added, infiltration rates could be increased. However, the current
plan for this particular pond is to eventually fill it completely with fines from the
washing process, and reclaim the land. The canal bottoms in the District’s system
appear to have much higher infiltration rates. The canals and other opportunities in
the area for active recharge basin development should be explored.
Recommended Action Plan
The Granite Capay facility pond has a low capability as a recharge facility and likely
should not be used for an active recharge program, however other gravel mining
facilities may be appropriate. The District’s canal system should be the focus of
future active recharge systems. This is due to higher infiltration rates in the canals
versus the gravel pit and the large size overall of the District system. Other gravel
pits in the Cache Creek system may be more appropriate for active groundwater
recharge.
Although not discussed earlier, but mentioned here, the gravel pits along the Cache
Creek system involve large amounts of administrative overhead due to coordination
of mining operations and safety, unusual wintertime water delivery systems, and
important environmental concerns. In contrast, the District’s existing canal system
is already designed to accept water, is efficient with no pumps, and may be ideal for
wintertime recharge. Over the next decades, the District should continue upgrading
its canal infrastructure with automated gates for wintertime recharge operations.
WEST ADAMS CANAL
HUNGRY HOLLOW CANAL
YOLO CENTRAL CANAL
MOO RE CANAL
COTTONWOOD CANAL
WILLOW CANAL
WALNUT CANAL
WIN
TERS CANA
LFAIRFIELD DITCH
MAPLE CANAL
UNIVER SITY DITCH
SOU
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COTTONWOOD SOUTH CANAL
GIBSON DITCH
ULRICH
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MAGNOLIA CANAL
FLIG
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STURM CANAL
MU
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REIF
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CLOVER CANAL
BUCKEYE CANAL
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SOF 0644R
SOF 0627L
SOF 0624R
SOF 0594R
SOF 0589L
SOF 0582RSOF 0577L
SOF 0568L
SOF 0563L
SOF 0550LSOF 0542R
SOF 0519L
SOF 0517R
SOF 0494L
SOF 0482R
SOF 0481H
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SOF 0429L
SOF 0429R
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MAP 0242L
MAP 0209R
MAP 0209L
MAP 0195RMAP 0180H
MAP 0177LMAP 0139R
MAP 0140LMAP 0109R
MAP 0108H
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MAP 0056R
MAP 0055L
MAP 0038L
ROG 0024S
ROG 0023R
ROG 0021R
ROG 0005RMAG 0154R
MAG 0129HMAG 0129R
MAG 0100R
MAG 0067R
ROS 0171L
ROS 0143L
ROS 0099L
ROS 0086L
ROS 0069L
ROS 0040R
ROS 0039R
MOR 0957L
MOR 0957R
MOR 0922L
MOR 0908R
MOR 0908L
MOR 0889R
MOR 0888R
MOR 0846LMOR 0846R
MOR 0822L
MOR 0821L
MOR 0760R
MOR 0760LMOR 0758H
MOR 0758R
MOR 0682LMOR 0681R
MOR 0665R MOR 0640LMOR 0638R
MOR 0637R MOR 0636L
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MOR 0526RMOR 0511L
MOR 0498LMOR 0498R
MOR 0486LMOR 0486RMOR 0472L
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MOR 0471R
MOR 0437R
MOR 0437L
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MOR 0401R
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MOR 0353H
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RFL 0021R
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CLV 0064H
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GDN 0122H
GDN 0122R
GDN 0118RGDN 0117B
GDN 0068R
GDN 0013R
GDN 0012R
HUH 0900H
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HUH 0810P
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HUH 0800H
HUH 0750R
HUH 0600R
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HUH 0523LHUH 0517L
HUH 0516L
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MAT 0011R
HUH 0438RHUH 0438L
HUH 0438HHUH 0391R
HUH 0392L
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HUH 0331L
HUH 0263R
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HUH 0209R
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ACA 0084R
ACA 0083R
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ESA 0102L
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WIN 1536L
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WIN 1335R
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WIN 1168L
WIN 1104L
WIN 1101L
WIN 1072L
WIN 1047L
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WIN 0955P
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WIN 0849LWIN 0847R
WIN 0829LWIN 0797L
WIN 0794L
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WIN 0386H
WIN 0367R
WIN 0305R
WIN 0268L
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WIL 2469LWIL 2377L
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WIL 1895L
WIL 1885L
WIL 1885RWIL 1854R
WIL 1844R
WIL 1815L
WIL 1777L
WIL 1760L
WIL 1735LWIL 1725L
WIL XXXXX
WIL 1711L
WIL 1683R
WIL 1656H
ULR 0172RULR 0113R
ULR 0079RULR 0048R
ULR 0014R
ULR 0013R
HIN 0100A
HIN 0100R
HIN 0098L
HIN 0050R
COW 0894R
COW 0849L
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MAP 0208L
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MOR 0907R
MOR 0436L
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South Fork Willow Slough
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Willow Slough Bypass
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C hickahominy Slough
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Goodnow Slough
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LegendKSAT in inches per hour
0"
0.06"
0.2"
0.5"
1.9"
5.9"
Sloughs
District Canal or Slough
District Pipeline
Private