EXPLANATION

Susquehanna

Potomac

James

Rappahannock

Appomattox

Pamunkey

Mattaponi

Patuxent

Choptank

River Input Monitoring station

Chesapeake Bay drainagearea boundary

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Monitoring Nutrients in the Major Rivers Draining to Chesapeake Bay

U.S. Department of the Interior, U.S. Geological Survey Prepared in cooperation with the Maryland Department of Natural Resources and Water-Resources Investigations Report 99-4238 the Virginia Department of Environmental Quality, Chesapeake Bay ProgramNovember 1999

Figure 1. Locations of major river basins and River Input Monitoring stations in the Chesapeake Bay Basin.

INTRODUCTION

Chesapeake Bay is the largestestuary in the United States, sup-porting an abundant and diversewildlife population and providingthousands of jobs in fishing, ship-ping, and recreation. Intensive agri-culture and continued developmentin the reg io n , ho weve r, h avedegraded the water quality of theBay, threatening its value as an eco-nomic and recreational resource.

Nutrients such as nitrogen andphosphorus are the pollutants ofgreatest concern affecting the Bay.Although nutrients are necessary forplant and animal life, in excessquantities they overnourish algae,causing algal blooms. These bloomsdeprive deeper waters of the sun-light and oxygen needed by aquaticorganisms. Suspended sediment isanother pollutant of concern; itdecreases water clarity and trans-ports bound nutrients.

In response to the environmentalproblems of the Bay, representativesof the Chesapeake Bay Commis-sion, the District of Columbia, theStates of Maryland, Pennsylvania,and Virginia, and the U.S. Environ-mental Protection Agency signedthe Chesapeake Bay Agreement in1987. This agreement committedFederal, State, and other agencies towork toward a 40-percent reductionin controllable nitrogen and phos-phorus inputs (based on 1985 levels)to the Bay by the year 2000.

In the mid-1980’s, the U.S. Geo-logical Survey (USGS), the Mary-land Department of the Environment(now part of the Maryland Depart-ment of Natural Resources), the Vir-ginia Department of EnvironmentalQuality (VDEQ), and the Metropoli-tan Washington Council of Govern-ments (MWCOG) established the

HIGHLIGHTS

• Collectively, the Susquehanna, the Potomac, and the James Rivers contributedabout 95 percent of the annual nitrogen load and about 87 percent of theannual phosphorus load from the nine major rivers draining to ChesapeakeBay from 1990 through 1998.

• The concentration of total nitrogen decreased significantly in six of the ninemonitored rivers from the mid-1980’s through 1998.

• The concentration of total phosphorus decreased significantly in four of thenine monitored rivers from the mid-1980’s through 1998.

• The cumulative effects of upgrades to wastewater treatment plants, the imple-mentation of best-management practices for controlling nonpoint-source pol-lution, and the ban of phosphate detergents contributed to a decrease innutrient concentrations.

• Natural increases in streamflow from the mid-1980’s through 1998 offset someof these decreases in nutrient concentrations.

Precipitation

IndustrialEmissions

DryDeposition

Infiltration

InfiltrationGround-waterDischarge to Stream

Discharge toStream

In-stream

ProcessesRunoff

Runoff

Runoff

Wind ErosionSpray Drift

River Input Monitoring (RIM) Pro-gram to quantify the loads and long-termtrends in concentrations of nutrients andsuspended sediment that enter the tidalpart of the Chesapeake Bay Basin from itsnine major tributaries (fig. 1). Results ofthe RIM program are being used to helpevaluate the effectiveness of strategiesaimed at reducing nutrients enteringChesapeake Bay from its tributaries.

Between 1985 and 1998, the USGScollected water samples from nine RIMstations, which collectively representabout 93 percent of the streamflow fromthe nontidal part of the 64,000-mi2

(square mile) Chesapeake Bay Basin.Water samples were collected monthly orbimonthly and during storms at each sta-tion for periods spanning from 8 to 14years. In Virginia and Maryland, supple-mental water samples were collected bythe VDEQ and MWCOG, respectively.

Nutrient concentrations, loads, andtrends observed at the RIM stations are animportant gauge of progress in reducingnutrient inputs to Chesapeake Bay fromits tributaries. These data also are used tocalibrate the Chesapeake Bay WatershedModel, a computer simulation of water-shed processes encompassing the entireChesapeake Bay Basin. Progress towardsthe 40-percent controllable nutrientreduction goal is estimated periodicallyusing this model, which accounts for bothpoint and nonpoint sources of nutrients.Data from the RIM stations and othermonitoring locations throughout theChesapeake Bay Basin should be consid-ered in conjunction with the results ofmodel simulations to evaluate improve-

ment in the water quality of ChesapeakeBay and its tributaries.

HOW DO NUTRIENTS AFFECTTHE BAY?

Nutrients are required by all plant andanimal life. Sources of nutrients tos t r e ams a r e b o th na tu r a l andhuman-derived, and include decayingorganic material; fertilizers applied tocrops, lawns, and golf courses; manurefrom fields or feedlots; atmosphericdeposition in the form of precipitation ordry deposition; ground-water discharge;and municipal wastewater discharge(fig. 2). Point sources of nutrients can beattributed to a single location, such as awastewater discharge pipe. Nonpoints o urc es o f n u t r i e n t s a r e w id e ly

distributed over an area, and may includeprecipitation, runoff from fields and urbanareas, and ground water discharged tostreams. In-stream processes affectc o n c e n t r a t i o n s o f n u t r i e n t s b ytransforming one chemical form toanother as a result of environmentalconditions or biological activity in thestream. These transformations can makeit difficult to determine the specificsources of the nutrients. Nutrients enterChesapeake Bay from streams, groundwater that discharges to the Bay, andatmospheric deposition. Elevated nutrientconcentrations cause excessive algaegrowth, which decreases the amount ofsunlight reaching the submerged aquaticvegetation that provides an importanthabitat and food source for fish and

Figure 2. Nutrient movement in the hydrologic cycle.

Table 1. Land area, land use, and major wastewater discharge upstream of the River Input Monitoring stations in Maryland and Virginia[mi2, square mile; Mgal/d, million gallons per day; land-use data from Vogelmann and others, 1998; land use as percentage of total land-surface area above each monitoring station; other land use includes barren/transitional and water]

USGS station number

Station name

Upstream land-surface

area (mi2)

Land use (percent) Major upstream wastewater discharge (Mgal/d)

Urban Agricultural Forested Other

01578310 Susquehanna River at Conowingo, Md. 27,100 2 29 67 2 437

01646580 Potomac River at Chain Bridge, Washington, D.C. 11,600 3 35 61 1 126

02035000 James River at Cartersville, Va. 6,260 1 16 80 3 89.4

01668000 Rappahannock River near Fredericksburg, Va. 1,600 1 36 61 2 4.7

02041650 Appomattox River at Matoaca, Va. 1,340 1 20 72 7 1.1

01673000 Pamunkey River near Hanover, Va. 1,081 1 24 68 7 5.0

01674500 Mattaponi River near Beulahville, Va. 601 1 19 69 11 .1

01594440 Patuxent River at Bowie, Md. 348 13 41 38 8 30

01491000 Choptank River near Greensboro, Md. 113 1 50 29 20 0

Table 1. Land area, land use, and major wastewater discharge upstream of the River Input Monitoring stations in Maryland and Virginia[mi2, square mile; Mgal/d, million gallons per day; land-use data from Vogelmann and others, 1998; land use as percentage of total land-surface area above each monitoring station; other land use includes barren/transitional and water]

USGS station number

Station name

Upstream land-surface

area (mi2)

Land use (percent) Major upstream wastewater discharge (Mgal/d)

Urban Agricultural Forested Other

01578310 Susquehanna River at Conowingo, Md. 27,100 2 29 67 2 437

01646580 Potomac River at Chain Bridge, Washington, D.C. 11,600 3 35 61 1 126

02035000 James River at Cartersville, Va. 6,260 1 16 80 3 89.4

01668000 Rappahannock River near Fredericksburg, Va. 1,600 1 36 61 2 4.7

02041650 Appomattox River at Matoaca, Va. 1,340 1 20 72 7 1.1

01673000 Pamunkey River near Hanover, Va. 1,081 1 24 68 7 5.0

01674500 Mattaponi River near Beulahville, Va. 601 1 19 69 11 .1

01594440 Patuxent River at Bowie, Md. 348 13 41 38 8 30

01491000 Choptank River near Greensboro, Md. 113 1 50 29 20 0

2

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IndustrialEmissions

DryDeposition

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Discharge toStream

In-stream

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Runoff

Runoff

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RANGE IN CONCENTRATION, 1985-1998

LOAD AND STREAMFLOW, 1990-1998

YIELD, 1990-1998

Mean annual streamflow

Mean annual load oftotal nitrogen

Mean annual streamflow

Mean annual load oftotal phosphorus

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90th percentile

75th percentile

25th percentile

10th percentile

median

wildl i fe . Decaying a lgae consumedissolved oxygen; reduced oxygen levelswill stress fish, crabs, molluscs, and otheraquatic organisms. It is expected thatachieving the 40-percent nut rient-reduction goal will greatly reduce algalblooms in the Bay, resulting in improvedwater clarity, increased submergedaquatic vegetation acreage, and higheroxygen levels year round.

WHAT HAS BEEN DONE TOREDUCE NUTRIENTS?

The major nutrient control strate-gies that have been used in the Chesa-peake Bay Basin include the following:

Upgrades to wastewater treatmentplants. Municipal and industrial waste-water treatment plants are the principalpoint sources of nutrients to streams. Inresponse to the Federal Water PollutionControl Act of 1972 and the Water Qual-ity Act of 1987, State and local govern-ments have increasingly supportedconsolidation of treatment plants and theuse of more effective technology in treat-ment of wastewater, including biologicalnutrient removal.

The ban of phosphate detergents.As replacements to phosphorus in deter-gents were found, detergents containingphosphate were taken off the market. Bythe late 1980’s, phosphate detergentswere banned in all the States that sur-round Chesapeake Bay.

The implementation of best man-agement practices (BMP’s). Engineer-ing and agricultural BMP’s are designedto minimize surface runoff of nutrientsand suspended material reaching streamsfrom nonpoint sources such as highways,construction sites, farms, and urban areas.Some BMP’s, however, can increasenutrient concentrations reaching streamsthrough ground water by diverting runoffaway from streams, instead allowingnutrient-rich water to infiltrate to groundwater that will eventually discharge to astream. Because ground water movesslowly, this process may take many years,making the effect of the BMP difficult toassess. Additionally, BMP’s are voluntaryfor landowners, are not easily monitored,and have different impacts in differentgeographic settings, which further com-plicates this assessment.

HOW ARE NUTRIENTS QUANTIFIEDAND COMPARED?

Several measures are used to quantifyamounts of nutrients, including concen-tration, load, and yield. Concentration,or analyzed mass of nutrient per volumeof water (usually reported in milligramsper liter, or mg/L), is used to assessin-stream conditions at the monitoringstations. Nutrient concentrations can dif-fer from stream to stream because of dif-ferences in land use, geology, streamflow,

point sources, and other factors in thedrainage basin. The relative percentagesof different land uses and the estimateddischarge from wastewater treatmentplants upstream from each RIM station(table 1) indicate how possible nutrientsources in the nine major basins compare.Load is the mass of nutrient transportedby streamflow over time, and is estimatedas the product of nutrient concentrationand streamflow (reported here in poundsper year, or lbs/yr). The three rivers that

Figure 3. Nutrient concentration ranges, nutrient loads, streamflow, and nutrient yields for the River Input Monitoring stations.

3

SUSQUEHANNA1

POTOMAC1

JAMES2

RAPPAHANNOCK2

APPOMATTOX3

PAMUNKEY3

MATTAPONI4

PATUXENT1

CHOPTANK1

-100 -100 -1000 0 0100 100 100

UPWARDTREND

UPWARDTREND

UPWARDTREND

DOWNWARDTREND

DOWNWARDTREND

DOWNWARDTREND

TOTAL PHOSPHORUSTOTAL NITROGENTOTAL SUSPENDED

MATERIALS5

150

PERCENT CHANGE IN CONCENTRATION

EXPLANATION

SIGNIFICANT

NONSIGNIFICANT

SIGNIFICANT

NONSIGNIFICANT

UNADJUSTED TREND6

FLOW-ADJUSTED TREND

have the highest flow—the Susquehanna,the Potomac, and the James Rivers—con-tribute the largest nutrient loads to thetidal part of the Chesapeake Bay Basin.Yield is the load per unit area of eachbasin (reported in pounds per year persquare mile, or lbs/yr/mi2), and is com-puted by dividing load by basin area.Because the influence of basin area onload is removed, yield is more useful thanload in comparing nutrient contributionsfrom basins of different sizes. The nutri-ent concentration, load, and yield for thenine major rivers draining to ChesapeakeBay are shown in figure 3 in order ofdecreasing basin area.

WHAT ARE THE NUTRIENT TRENDS INTHE NINE RIVERS DRAINING TO

THE BAY?

Trends are overal l increases ordecreases in a measurement such as con-centration during a specified period.Trends in nutrient concentrations can be

affected by nutrient control strategies,which manage point and nonpoint sourcesin an effort to achieve downward trends.In many cases, concentration trends arealso affected by natural processes, espe-cially streamflow. If a point source, suchas discharge from a wastewater treatmentplant, is the dominant nutrient source to astream, dilution from an increase instreamflow would cause a downwardtrend in nutrient concentrations. In con-trast, if a nonpoint source, such as runofffrom agricultural land, is the dominantnutrient source, increased streamflowfrom an increase in storm runoff wouldcause an upward trend in nutrient concen-trations. Often, a decrease in nutrient con-centrations resulting from a BMP can beoffset by an increase in concentrationsresulting from higher streamflow.

The removal of streamflow as a vari-able affecting in-stream concentrations ofnutrients in a trend analysis allows trendscaused by other factors to be identified,

and the effects of nutrient control strate-gies to be assessed. These flow-adjustedconcentration trends are independent ofvariation in streamflow. When consider-ing the health of aquatic organisms inChesapeake Bay and its tributaries, how-ever, trends due to both streamflow andnutrient control strategies must be exam-ined, as both influence the overall state ofthe ecosystem. These unadjusted con-centration trends account for all factorsthat affect trends in nutrient concentra-tions.

Data collected from the mid-to-late1980’s through 1998 were used to identifytrends in total nitrogen and total phospho-rus concentrations at the RIM stations.Trends in streamflow and concentrationsof suspended material, which transportsbound nutrients, also were identified;these may provide additional insight intonutrient trends. Both the unadjusted andflow-adjusted concentration trends arepresented in figure 4 as 95-percent confi-

dence intervals—the interval inwhich there is a 95-percent proba-bility that the true trend falls.Directions of flow-adjusted con-centration trends are presented foreach drainage basin in figure 5,and directions of unadjusted con-centration trends are presented infigure 6. Directions of trends instreamflow are presented for eachdrainage basin in figure 7. Adetailed discussion of the meth-odologies and results of the trendanalyses is presented in Langlandand others (1999).

Susquehanna River

The Susquehanna River moni-toring station is at the ConowingoDam Hydroelectric Power Plantin Conowingo, Md. The station isapproximately 10 miles from theriver mouth and receives stream-flow from 99 percent of the27,510-mi2 Susquehanna RiverBasin. The Susquehanna River isthe largest river draining to theBay and contributes about 60 per-cent of the total streamflow, 62percent of the total nitrogen load,and 34 percent of the total phos-phorus load from the nontidal partof the Chesapeake Bay Basin.

Figure 4. Flow-adjusted and unadjusted trends in concentration of selected constituents at the River Input Monitoring stations. (Cross hatching indicates the trend was significant at the 95-percent confidence level.)1 Sampling period was Jan. 1985-Dec. 1998.2 Sampling period was July 1988-Dec. 1998.3 Sampling period was July 1989-Dec. 1998.4 Sampling period was Oct. 1989-Dec. 1998.5 Total suspended sediment (analyzed using the entire sample) was measured at stations on the Susquehanna, the Potomac, the Patuxent, and the Choptank Rivers. Total suspended solids (analyzed using part of the sample) was measured at the other stations.6 Unadjusted concentration trends reported here are the same as flow-weighted concentration trends as reported in Langland and others, 1999.

4

EXPLANATION

Basin

Rappahannock

Appomattox

Pamunkey

Mattaponi

Patuxent

Choptank

Downward trend

No significanttrend detected

Susquehanna

Potomac

James

(A) (B)The Susquehanna Riverdrains parts of New York,Pennsylvania, and Mary-land, and includes some ofthe most productive agricul-tural land in the nation.Agricultural act ivi ty isextensive in the lower Sus-quehanna River Basin, con-tributing to the high yield ofnitrogen (fig. 3). However,the phosphorus yield waslow, because phosphorustends to bind to sedimentparticles that settle to theriver bottom and becometrapped behind ConowingoDam (Langland and Hainly,1997).

The flow-adjusted con-centration of total nitrogendecreased about 12 to 25percent at the SusquehannaRiver monitoring station during 1985-98(fig. 4). The implementation of agricul-tural and forestry BMP’s may be partlyresponsible for the decrease in total nitro-gen. The unadjusted concentration of totalnitrogen also decreased about 20 percent.Trends in flow-adjusted and unadjustedconcentrations were comparable becausethere was no significant increase in flowat this station during 1985-98 (fig. 7) tooffset the effects of nutrient control strate-gies in the basin.

The flow-adjusted concentration oftotal phosphorus decreased about 36 to 60percent during the 14-year monitoringper iod. Inputs f rom point sources,although not major contributors to thetotal phosphorus load at the SusquehannaRiver monitoring station, decreased by 56percent (Darrell and others, 1999). Thedecrease in phosphorus may be partlyattributed to the phosphate detergent banand to agricultural BMP’s. There was a 57to 75 percent decrease in unadjusted totalphosphorus concentration.

Potomac River

The Potomac River is the second larg-est river draining to the Bay and the sec-ond largest source of nitrogen andphosphorus. It contributes about 20 per-cent of the total streamflow, 28 percent ofthe total nitrogen load, and 33 percent of

the total phosphorus load from the non-tidal part of the Chesapeake Bay Basin.The Potomac River monitoring station, atChain Bridge in Washington, D.C.,receives streamflow from 80 percent ofthe 14,670-mi2 Potomac River Basin.Because the monitoring station liesupstream from the municipal wastewaterdischarges in the Metropolitan Washing-ton, D.C., area, water-quality characteris-tics and trends discussed in this report donot reflect contributions or changes inthese wastewater discharges.

Dur ing the per iod 1985-98, theflow-adjusted concentration of total nitro-gen at the Potomac River monitoring sta-tion did not show a significant trend(fig. 4), even though inputs from pointsources of nitrogen above the station werereduced by about 10 percent during the14-year period (Darrell and others, 1999).The unadjusted concentration of totalnitrogen also did not show a significanttrend, even though streamflow increasedduring that period (fig. 7).

The flow-adjusted phosphorus con-centration decreased about 40 to 60 per-cent during the 14-year period. Pointsource inputs of phosphorus above themonitoring station were reduced by about28 percent (Darrell and others, 1999),largely due to the phosphate detergentban. Nonpoint source inputs of phospho-

rus also were reduced. Because phospho-rus tends to bind to sediment, the decreasein both phosphorus and suspended mate-rial (fig. 4) may indicate the effectivenessof BMP’s aimed at controlling sedimenterosion. The success of these nutrientcontrol strategies on total phosphorusconcentration was offset by the increasein flow, however, as the unadjusted totalphosphorus concentra t ion did notdecrease significantly.

James River

The James River monitoring station, atCartersville, Va., receives streamflowfrom about 60 percent of the 10,200-mi2

James River Basin. It is located upstreamfrom municipal wastewater discharges inthe Richmond, Va., area. Of the nine riv-ers monitored, it contributes about 12 per-cent of the streamflow, 5 percent of thetotal nitrogen load, and 20 percent of thetotal phosphorus load, making it the thirdlargest nutrient and streamflow sourceafter the Susquehanna and the PotomacRivers. The James River Basin has thesecond largest yield of total phosphorus inthe nontidal part of the Chesapeake BayBasin (fig. 3). The relatively large phos-phorus yield is caused by both point andnonpoint sources, including wastewatertreatment plants, high concentrationsbound to sediment in agricultural runoff,

Figure 5. Trends in flow-adjusted total nitrogen (A) and total phosphorus (B) concentrations in the Chesapeake Bay Basin from the mid-to-late 1980’s through 1998.

5

Rappahannock

Appomattox

Pamunkey

Mattaponi

Patuxent

Choptank

Downward trend

No significanttrend detected

Susquehanna

Potomac

James

(A) (B)EXPLANATION

Basin

and naturally high concentrations fromsoils and rocks.

A downward trend of about 44 to 69percent in the flow-adjusted concentrationof total phosphorus was detected at theJames River monitoring station during theperiod 1988-98 (fig. 4). This downwardtrend was more evident in low-flow con-ditions than in high-flow conditions (Belland others, 1996), and most of thedecrease occurred during 1988-90, soonafter the phosphate detergent ban wasimplemented in Virginia. This suggeststhat point-source reductions were themost effective nutrient control strategy inthis basin during the period monitored.The unadjusted total phosphorus concen-tration decreased about 48 to 61 percent.

During the 11-year monitoring period,the flow-adjusted concentration of totalnitrogen in the James River decreasedabout 5 to 30 percent. With no significantincrease in streamflow (fig. 7) to offsetthe effects of BMP’s, the unadjusted con-centration of total nitrogen also decreasedabout 4 to 34 percent.

Rappahannock River

The Rappahannock River monitoringstation, upstream from Fredericksburg,Va., receives streamflow from about 57percent of the 2,800-mi2 RappahannockRiver Basin. This river contributes about

3 percent of the total streamflow, 2 per-cent of the total nitrogen load, and 8 per-cent o f the to ta l phosphorus loaddelivered annually from the nontidal partof the Chesapeake Bay Basin. The Rappa-hannock River Basin has the largest per-centage of agricultural land among thefive monitored river basins in Virginiaand the third largest of all nine basins(table 3). Nonpoint sources contributemore than 90 percent of the nutrient loadin this basin, although a few point sourcesalso are present. Steep slopes and abun-dant pastureland in the basin cause theRappahannock River to produce highyields of suspended material and the high-est yield of total phosphorus (fig. 3).

The flow-adjusted concentrations oftotal nitrogen and total phosphorusdecreased at the Rappahannock Rivermonitoring station about 21 to 41 percentand 41 to 76 percent, respectively, duringthe period 1988-98 (fig. 4). The imple-mentation of agricultural and forestryBMP’s potentially was a major factor inthese trends. The Virginia Department ofConservation and Recreation estimatesthat between 1985 and 1993 there wasabout an 11 percent decrease in nitrogenand about an 18 percent decrease in phos-phorus from nonpoint sources (Mark Ben-nett, Virginia Department of Conservationand Recreation, written commun., 1996).

Any decrease in phosphorus concentra-tion as a consequence of the phosphatedetergent ban probably would not havebeen evident because of the limited num-ber of point sources in the basin upstreamfrom the monitoring station.

The unadjusted concentrations of totalnitrogen and total phosphorus did notchange significantly during the 11-yearmonitoring period, indicating that naturalstreamflow variations and increasingdevelopment in this basin may have offsetnutrient reductions resulting from theimplementation of BMP’s.

Appomattox River

The Appomattox River monitoringstation, at Matoaca, Va., receives stream-flow from approximately 84 percent ofthe 1,600-mi2 Appomattox River Basin.This river contributes about 2 percent ofthe total streamflow, less than 1 percent ofthe total nitrogen load, and 1 percent ofthe total phosphorus load delivered annu-ally from the nontidal part of the Chesa-peake Bay Basin. Sediment with boundnutrients settles behind Lake ChesdinDam, 2.8 miles upstream from the moni-toring station, contributing to the secondsmallest yields of total phosphorus andtotal nitrogen of the nine major basins(fig 3).

Flow-adjusted total nitrogen concen-trations decreased about 10 to27 percent during the period1989-98 (fig. 4). Unadjustedtotal nitrogen concentrationsdecreased about 14 to 22 per-cent. The similarity betweenthese values results from alack of increase in streamflowduring this period (fig. 7).The implementation of agri-cultural BMP’s may be partlyresponsible for the decrease intotal nitrogen. There were nosignificant trends in eitherflow-adjusted or unadjustedtotal phosphorus concentra-tions during the 10-year mon-i t o r ing pe r iod . Becausenonpoint sources contributealmost all of the nutrient loadto the river, the phosphatedetergent ban had little effecton phosphorus concentrationtrends.

Figure 6. Trends in unadjusted total nitrogen (A) and total phosphorus (B) concentrations in the Ches-apeake Bay Basin from the mid-to-late 1980’s through 1998.

6

Rappahannock

Appomattox

Pamunkey

Mattaponi

Patuxent

Choptank

Upward trend

No significanttrend detected

Susquehanna

Potomac

EXPLANATION

James

Basin

Pamunkey River

The Pamunkey and Mattaponi Riversjoin below the Pamunkey River monitor-ing station to form the York River, whichflows to Chesapeake Bay. The PamunkeyRiver monitoring station, near Hanover,Va., receives streamflow from about 45percent of the 2,400-mi2 York RiverBasin. The Pamunkey River contributesabout 2 percent of the total streamflow,less than 1 percent of the total nitrogenload, and 2 percent of the total phospho-rus load delivered annually from the non-tidal part of the Chesapeake Bay Basin.The basin has the third smallest yield oftotal nitrogen and the fourth smallestyield of total phosphorus (fig. 3). Thebasin is relatively flat, contains expansesof forested wetlands and marshes, andreceives nutrients from both nonpoint andpoint sources, including agricultural run-off and discharge from wastewater treat-ment plants.

No significant trends in flow-adjustedor unadjusted concentrations of totalnitrogen or total phosphorus were evidentat the Pamunkey River monitoring stationduring the period 1989-98 (fig. 4).

Mattaponi River

The Mattaponi River monitoring sta-tion, near Beulahville, Va., receivesstreamflow from about 25 percent of the2,400-mi2 York River Basin. The Mat-taponi River contributes less than 1 per-cent of the total streamflow, the totalnitrogen load, and the total phosphorusload delivered annually from the nontidalpart of the Chesapeake Bay Basin. TheMattaponi River Basin is relatively flatand contains expanses of wetland areas.Because of the small area and low reliefof this basin, the Mattaponi River has thesecond smallest annual load of both totalnitrogen and total phosphorus, after theChoptank River (fig. 3); however, yieldsof total nitrogen and total phosphorusfrom the Mattaponi River are the small-est. Nonpoint sources contribute most ofthe nutrients to the river.

Both flow-adjusted and unadjustedtotal nitrogen concentrations decreasedabout 20 to 35 percent during the period1989-1998 (fig. 4). Both flow-adjustedand unadjusted total phosphorus concen-trations decreased about 30 to 45 percent

during the 10-year mon-itoring period. The simi-lar i ty between thesevalues reflects the lackof a significant increasein streamflow duringth i s p e r io d ( f i g . 7 ) .Because of the smallnumber of point sourcesin the Mattaponi RiverBasin, the decreases intotal nitrogen and totalphosphorus concentra-t ions probably werecaused by changes innonpoin t sources o rin-stream processes.

Patuxent River

The Patuxent Rivermonitoring station, inBowie, Md., receivesstreamflow from about37 percent of the 932-mi2 Patuxent RiverBasin. The basin lies completely withinMaryland, between Baltimore and Wash-ington, D.C., in an area of increasingurbanization. The Patuxent River contrib-utes less than 1 percent of the totalstreamflow, the total nitrogen load, andthe total phosphorus load delivered annu-ally from the nontidal part of the Chesa-peake Bay Basin. Water quali ty isstrongly affected by urban runoff and byeight was tewater t reatment plan tsupstream from the station. Because it isaffected by relatively large number ofpoint sources, the Patuxent River has thehighest median concentrations of totalnitrogen and total phosphorus, as well asrelatively large yields for both nutrients(fig. 3).

The flow-adjusted concentration oftotal nitrogen decreased about 60 to 70percent during 1985-98 (fig. 4). Withinthe same period, point source inputs ofnitrogen were reduced by 53 percent(Darrell and others, 1999), largely as aresult of implementation of biologicalnutrient removal at major wastewatertreatment plants between 1991 and 1993.Nutrient control strategies apparentlyhave been particularly effective in thisbasin, as an increase in streamflow duringthe 14-year period did not offset these

improvements. Unadjusted concentrationsof total nitrogen also decreased about 63to 68 percent.

The flow-adjusted concentration oftotal phosphorus decreased about 78 to 90percent during the 14-year monitoringperiod (fig. 4). Inputs of phosphorus frompoint sources were reduced by about 75percent during this period, largely due tothe phosphate detergent ban. Increasedstreamflow (fig. 7) offset total phospho-rus reductions more than total nitrogenreductions, but the unadjusted total phos-phorus concentration still decreased about72 to 76 percent during the 14-yearperiod.

Choptank River

The Choptank River monitoring sta-tion, in Greensboro, Md., receives stream-flow from about 14 percent of the 795-mi2

Choptank River Basin. The ChoptankRiver is the largest river on Maryland’sEastern Shore, but contributes less than 1percent of the streamflow, the total nitro-gen load, and the total phosphorus loaddelivered annually from the nontidal partof the Chesapeake Bay Basin. Land use inthe basin is primarily agricultural, pro-ducing the fourth largest yield of totalnitrogen and the fifth largest yield of totalphosphorus (fig. 3).

Figure 7. Trends in streamflow (monthly mean discharge) in the Chesapeake Bay Basin from the mid-to-late 1980’s through 1998.

7

Fo r t h e p e r i o d 1 9 8 5 - 9 8 , t h eflow-adjusted concentration of total nitro-gen did not change significantly while theunadjusted concentration of total nitrogendecreased about 6 to 9 percent (fig. 4).The flow-adjusted concentration of totalphosphorus decreased about 13 to 39 per-cent during the 14-year period. Thisdecrease likely is a function of theapproximately 50-percent decrease in theflow-adjusted concentration of total sus-pended material (fig. 4). No known pointsources of nutrients exist upstream of themonitoring station on the ChoptankRiver; therefore, these decreases are prob-ably due to nonpoint-source reductions.The unadjusted total phosphorus concen-tration did not reflect the improvementsfrom these nutrient control strategies, asno significant decrease was detected. Thiswas likely a result of increased stream-flow during the monitoring per iod(fig. 7).

WHAT PROGRESS IS BEINGMADE TOWARD THE

40-PERCENT NUTRIENTREDUCTION GOAL?

Many of the major rivers draining toChesapeake Bay are showing significantprogress toward the goal of a 40-percentreduction in controllable nutrients man-dated by the Chesapeake Bay Agreementin 1987. The effects of BMP’s are beingobserved across the Bay basin, but naturalincreases in streamflow during the moni-toring period have often counteractedthese improvements. In some rivers, how-ever, significant reductions have not beenachieved.

As the States of Maryland, Pennsylva-nia, and Virginia, and the District ofColumbia assess their progress toward thenutrient-reduction goal, they will imple-ment tributary strategies for the nontidalareas of Chesapeake Bay, including theareas monitored by the River Input Moni-toring Program (Virginia Secretary ofNatural Resources and others, 1998;Mary land Depa r tment o f Natu ra lResources and others, 1999). These strat-egies contain specific plans for reducingnutrients in individual river basins, andare expected to lead to substantial reduc-tions in nutrients reaching ChesapeakeBay from its tributaries in coming years.

SELECTED REFERENCES

Bell, C.F., Belval, D.L., and Campbell, J.P.,1996, Trends in nutrients and suspended sol-ids at the Fall Line of five tributaries to theChesapeake Bay, Virginia, July 1988through June 1995: U.S. Geological SurveyWater-Resources Investigations Report96-4191, 37 p.

Darrell, L.C., Feit-Majedi, B., Lizarraga, J.S.,and Blomquist, J.D., 1999, Nutrient and sus-pended-sediment concentrations, trends,loads, and yields from the non-tidal part ofthe Susquehanna, Potomac, Patuxent, andChoptank Rivers, 1985-96: U.S. GeologicalSurvey Water Resources InvestigationsReport 98-4177, 39 p.

Langland, M.J., and Hainly, R.A., 1997,Changes in bottom-surface elevations inthree reservoirs on the lower SusquehannaRiver, Pennsylvania and Maryland, follow-ing the January 1996 flood: Implications fornutrient and sediment loads to the Chesa-peake Bay: U.S. Geological SurveyWater-Resources Investigations Report97-4138, 34 p.

Langland, M.J., Blomquist, J.D., Sprague,L.A., and Edwards, R.E., 1999, Trends andstatus of flow, nutrients, and sediments forselected nontidal programs in the Chesa-peake Bay Watershed, 1985-98: U.S. Geo-logical Survey Open-File Report 99-451,64 p.

Maryland Department of Natural Resources,Maryland Department of Agriculture, Mary-land Department of the Environment, Mary-land Office of Planning, and the Universityof Maryland, 1999, Maryland’s tributaryteams: Annual Report 1998, 94 p.

Virginia Secretary of Natural Resources, Vir-ginia Department of Conservation and Rec-reation, and Virginia Department ofEnvironmental Quality, 1998, Third annualreport on the development and implementa-tion of nutrient reduction strategies for Vir-ginia’s tributaries to the Chesapeake Bay,100 p.

Vogelmann, J.E., Sohl, T.L., Campbell, P.V.,and Shaw, D.M., 1998, Regional land covercharacterization using Landsat ThematicMapper data and ancillary data sources,Third EMAP Research Symposium, Albany,N.Y., April 8-11, 1997, Environmental Mon-itoring and Assessment, v. 51, p. 415-428.

By Donna L. Belval and Lori A. Sprague

FOR MORE INFORMATION

For more information on USGS activi-ties in Virginia and Maryland, please contact the following:

District ChiefU.S. Geological Survey1730 East Parham RoadRichmond, VA 23228Phone: 804-261-2600or 800-684-1592

District ChiefU.S. Geological Survey8987 Yellow Brick RoadBaltimore, MD 21237Phone: 410-238-4200or 888-826-3130

Or visit our web sites at:http://va.water.usgs.gov/http://md.water.usgs.gov/

Additional information and data from the River Input Monitoring Program can be found at:

Information on USGS activities in the Chesapeake Bay Region can be found at:

http://chesapeake.usgs.gov/chesbay/

Information on other Federal, State, and Citizen Programs can be found on the EPA’s Chesapeake Bay Home Page at:

http://www.chesapeakebay.net/

For more information on USGS ser-vices and products, call:

1-888-ASK-USGS

or visit the USGS Home Page at:

http://www.usgs.gov/

http://va.water.usgs.gov/chesbay/RIMP/