Monitoring Nutrients in the Major Rivers Draining to Chesapeake

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Monitoring Nutrients in the Major Rivers Draining to Chesapeake Bay INTRODUCTION HIGHLIGHTS Chesapeake Bay is the largest • Collectively, the Susquehanna, the Potomac, and the James Rivers contributed estuary in the United States, sup- about 95 percent of the annual nitrogen load and about 87 percent of the porting an abundant and diverse annual phosphorus load from the nine major rivers draining to Chesapeake wildlife population and providing Bay from 1990 through 1998. thousands of jobs in fishing, ship- ping, and recreation. Intensive agri- • The concentration of total nitrogen decreased significantly in six of the nine culture and continued development monitored rivers from the mid-1980’s through 1998. in the region, however, have • The concentration of total phosphorus decreased significantly in four of the degraded the water quality of the nine monitored rivers from the mid-1980’s through 1998. Bay, threatening its value as an eco- nomic and recreational resource. • The cumulative effects of upgrades to wastewater treatment plants, the imple- Nutrients such as nitrogen and mentation of best-management practices for controlling nonpoint-source pol- phosphorus are the pollutants of lution, and the ban of phosphate detergents contributed to a decrease in greatest concern affecting the Bay. nutrient concentrations. Although nutrients are necessary for • Natural increases in streamflow from the mid-1980’s through 1998 offset some plant and animal life, in excess of these decreases in nutrient concentrations. quantities they overnourish algae, causing algal blooms. These blooms deprive deeper waters of the sunlight and oxygen needed by aquatic 77º 75º 43º organisms. Suspended sediment is another pollutant of concern; it 80º 75º 45º decreases water clarity and transports bound nutrients. NEW YORK PENNSYLVANIA In response to the environmental problems of the Bay, representatives of the Chesapeake Bay Commis- 40º EXPLANATION 41º sion, the District of Columbia, the Basin States of Maryland, Pennsylvania, Susquehanna Potomac and Virginia, and the U.S. Environ- James mental Protection Agency signed

79º Rappahannock the Chesapeake Bay Agreement in Appomattox MARYLAND 1987. This agreement committed Pamunkey DELAWARE Mattaponi Federal, State, and other agencies to OCEAN Patuxent work toward a 40-percent reduction 39º Choptank D.C. in controllable nitrogen and phos- WEST VIRGINIA VIRGINIA Chesapeake Bay drainage phorus inputs (based on 1985 levels) area boundary CHESAPEAKE to the Bay by the year 2000. River Input Monitoring station In the mid-1980’s, the U.S. Geo- logical Survey (USGS), the Mary- land Department of the Environment BAY (now part of the Maryland Depart- ATLANTIC 0 20 MILES ment of Natural Resources), the Vir- 0 20 KILOMETERS ginia Department of Environmental Quality (VDEQ), and the Metropoli- Figure 1. Locations of major river basins and River Input Monitoring stations in the tan Washington Council of Govern- Chesapeake Bay Basin. ments (MWCOG) established the

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 Program November 1999 River Input Monitoring (RIM) Pro- gram to quantify the loads and long-term trends in concentrations of nutrients and suspended sediment that enter the tidal part of the Chesapeake Bay Basin from its nine major tributaries (fig. 1). Results of the RIM program are being used to help Precipitation Dry evaluate the effectiveness of strategies Deposition aimed at reducing nutrients entering Industrial Chesapeake Bay from its tributaries. Emissions Between 1985 and 1998, the USGS Runoff collected water samples from nine RIM Wind Erosion stations, which collectively represent Spray Drift Discharge to about 93 percent of the streamflow from Stream the nontidal part of the 64,000-mi2 Runoff (square mile) Chesapeake Bay Basin. Infiltration In-stream Water samples were collected monthly or Processes Runoff bimonthly and during storms at each sta- Ground-water Infiltration tion for periods spanning from 8 to 14 Discharge to Stream years. In Virginia and Maryland, supple- mental water samples were collected by Figure 2. Nutrient movement in the hydrologic cycle. the VDEQ and MWCOG, respectively. Nutrient concentrations, loads, and ment in the water quality of Chesapeake distributed over an area, and may include trends observed at the RIM stations are an Bay and its tributaries. precipitation, runoff from fields and urban important gauge of progress in reducing areas, and ground water discharged to HOW DO NUTRIENTS AFFECT nutrient inputs to Chesapeake Bay from streams. In-stream processes affect THE BAY? its tributaries. These data also are used to concentrations of nutrients by calibrate the Chesapeake Bay Watershed Nutrients are required by all plant and transforming one chemical form to Model, a computer simulation of water- animal life. Sources of nutrients to another as a result of environmental shed processes encompassing the entire streams are both natural and conditions or biological activity in the Chesapeake Bay Basin. Progress towards human-derived, and include decaying stream. These transformations can make the 40-percent controllable nutrient organic material; fertilizers applied to it difficult to determine the specific reduction goal is estimated periodically crops, lawns, and golf courses; manure sources of the nutrients. Nutrients enter using this model, which accounts for both from fields or feedlots; atmospheric Chesapeake Bay from streams, ground point and nonpoint sources of nutrients. deposition in the form of precipitation or water that discharges to the Bay, and Data from the RIM stations and other dry deposition; ground-water discharge; atmospheric deposition. Elevated nutrient monitoring locations throughout the and municipal wastewater discharge concentrations cause excessive algae Chesapeake Bay Basin should be consid- (fig. 2). Point sources of nutrients can be growth, which decreases the amount of ered in conjunction with the results of attributed to a single location, such as a sunlight reaching the submerged aquatic model simulations to evaluate improve- wastewater discharge pipe. Nonpoint vegetation that provides an important sources of nutrients are widely habitat and food source for fish and

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]

Land use (percent) Major upstream USGS Upstream wastewater station land-surface Station name discharge number area (mi2) Urban Agricultural Forested Other (Mgal/d) 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 wildlife. Decaying algae consume HOW ARE NUTRIENTS QUANTIFIED point sources, and other factors in the dissolved oxygen; reduced oxygen levels AND COMPARED? drainage basin. The relative percentages will stress fish, crabs, molluscs, and other Several measures are used to quantify of different land uses and the estimated aquatic organisms. It is expected that amounts of nutrients, including concen- discharge from wastewater treatment achieving the 40-percent nutrient- tration, load, and yield. Concentration, plants upstream from each RIM station reduction goal will greatly reduce algal or analyzed mass of nutrient per volume (table 1) indicate how possible nutrient blooms in the Bay, resulting in improved of water (usually reported in milligrams sources in the nine major basins compare. water clarity, increased submerged per liter, or mg/L), is used to assess Load is the mass of nutrient transported aquatic vegetation acreage, and higher in-stream conditions at the monitoring by streamflow over time, and is estimated oxygen levels year round. stations. Nutrient concentrations can dif- as the product of nutrient concentration fer from stream to stream because of dif- and streamflow (reported here in pounds WHAT HAS BEEN DONE TO per year, or lbs/yr). The three rivers that REDUCE NUTRIENTS? ferences in land use, geology, streamflow, The major nutrient control strate- TOTAL NITROGEN TOTAL PHOSPHORUS gies that have been used in the Chesa- RANGE IN CONCENTRATION, 1985-1998 peake Bay Basin include the following: 8 0.5 Upgrades to wastewater treatment 90th percentile plants. Municipal and industrial waste- 75th percentile 0.4 6 median water treatment plants are the principal 25th percentile point sources of nutrients to streams. In 0.3 10th percentile response to the Federal Water Pollution 4 Control Act of 1972 and the Water Qual- 0.2 2 ity Act of 1987, State and local govern- 0.1 CONCENTRATION, IN CONCENTRATION, ments have increasingly supported MILLIGRAMS PER LITER consolidation of treatment plants and the 0 0 use of more effective technology in treatment of wastewater, including biological nutrient removal. LOAD AND STREAMFLOW, 1990-1998 The ban of phosphate detergents. 5,000,000 50,000 As replacements to phosphorus in deter- 150,000,000 4,000,000 40,000 gents were found, detergents containing Mean annual streamflow Mean annual streamflow phosphate were taken off the market. By Mean annual load of Mean annual load of 100,000,000 total nitrogen 3,000,000 total phosphorus 30,000 the late 1980’s, phosphate detergents were banned in all the States that sur- 2,000,000 20,000 round Chesapeake Bay. 50,000,000 The implementation of best man- 1,000,000 10,000 IN STREAMFLOW, CUBIC FEET PER SECOND agement practices (BMP’s). Engineer- IN POUNDS PERLOAD, YEAR 0 0 0 ing and agricultural BMP’s are designed to minimize surface runoff of nutrients and suspended material reaching streams YIELD, 1990-1998 from nonpoint sources such as highways, 800 construction sites, farms, and urban areas. 6,000

Some BMP’s, however, can increase 600 nutrient concentrations reaching streams 4,000 through ground water by diverting runoff 400 away from streams, instead allowing nutrient-rich water to infiltrate to ground 2,000 200 water that will eventually discharge to a MILE PER SQUARE stream. Because ground water moves YIELD, IN POUNDS PERYIELD, YEAR slowly, this process may take many years, 0 0 making the effect of the BMP difficult to James James Patuxent Patuxent Potomac Potomac Choptank Choptank Mattaponi Mattaponi Pamunkey assess. Additionally, BMP’s are voluntary Pamunkey Appomattox Appomattox Susquehanna for landowners, are not easily monitored, Susquehanna Rappahannock Rappahannock and have different impacts in different geographic settings, which further com- Figure 3. Nutrient concentration ranges, nutrient loads, streamflow, and nutrient yields for plicates this assessment. the River Input Monitoring stations.

3 have the highest flow—the Susquehanna, affected by nutrient control strategies, and the effects of nutrient control strate- the Potomac, and the James Rivers—con- which manage point and nonpoint sources gies to be assessed. These flow-adjusted tribute the largest nutrient loads to the in an effort to achieve downward trends. concentration trends are independent of tidal part of the Chesapeake Bay Basin. In many cases, concentration trends are variation in streamflow. When consider- Yield is the load per unit area of each also affected by natural processes, espe- ing the health of aquatic organisms in basin (reported in pounds per year per cially streamflow. If a point source, such Chesapeake Bay and its tributaries, how- square mile, or lbs/yr/mi2), and is com- as discharge from a wastewater treatment ever, trends due to both streamflow and puted by dividing load by basin area. plant, is the dominant nutrient source to a nutrient control strategies must be exam- Because the influence of basin area on stream, dilution from an increase in ined, as both influence the overall state of load is removed, yield is more useful than streamflow would cause a downward the ecosystem. These unadjusted con- load in comparing nutrient contributions trend in nutrient concentrations. In concentration trends account for all factors from basins of different sizes. The nutri- trast, if a nonpoint source, such as runoff that affect trends in nutrient concentra- ent concentration, load, and yield for the from agricultural land, is the dominant tions. nine major rivers draining to Chesapeake nutrient source, increased streamflow Data collected from the mid-to-late Bay are shown in figure 3 in order of from an increase in storm runoff would 1980’s through 1998 were used to identify decreasing basin area. cause an upward trend in nutrient concen- trends in total nitrogen and total phospho- trations. Often, a decrease in nutrient con- rus concentrations at the RIM stations. WHAT ARE THE NUTRIENT TRENDS IN centrations resulting from a BMP can be Trends in streamflow and concentrations THE NINE RIVERS DRAINING TO offset by an increase in concentrations of suspended material, which transports THE BAY? resulting from higher streamflow. bound nutrients, also were identified; Trends are overall increases or The removal of streamflow as a vari- these may provide additional insight into decreases in a measurement such as con- able affecting in-stream concentrations of nutrient trends. Both the unadjusted and centration during a specified period. nutrients in a trend analysis allows trends flow-adjusted concentration trends are Trends in nutrient concentrations can be caused by other factors to be identified, presented in figure 4 as 95-percent confidence intervals—the interval in TOTAL SUSPENDED which there is a 95-percent proba- TOTAL NITROGEN TOTAL PHOSPHORUS 5 MATERIALS bility that the true trend falls. DOWNWARD UPWARD DOWNWARD UPWARD DOWNWARD UPWARD Directions of flow-adjusted con- TREND TREND TREND TREND TREND TREND 1 centration trends are presented for SUSQUEHANNA 1 each drainage basin in figure 5, POTOMAC 2 and directions of unadjusted con- JAMES centration trends are presented in 2 RAPPAHANNOCK 150 figure 6. Directions of trends in 3 APPOMATTOX streamflow are presented for each 3 PAMUNKEY drainage basin in figure 7. A 4 MATTAPONI detailed discussion of the meth- 1 PATUXENT odologies and results of the trend 1 analyses is presented in Langland CHOPTANK -10000100 -100100 -100 0100 and others (1999). PERCENT CHANGE IN CONCENTRATION Susquehanna River EXPLANATION 6 The Susquehanna River moni- UNADJUSTED TREND FLOW-ADJUSTED TREND SIGNIFICANT SIGNIFICANT toring station is at the Conowingo Dam Hydroelectric Power Plant NONSIGNIFICANT NONSIGNIFICANT in Conowingo, Md. The station is approximately 10 miles from the Figure 4. Flow-adjusted and unadjusted trends in concentration of selected constituents at the river mouth and receives stream- River Input Monitoring stations. (Cross hatching indicates the trend was significant at the 95-percent confidence level.) flow from 99 percent of the 2 1 Sampling period was Jan. 1985-Dec. 1998. 27,510-mi Susquehanna River 2 Sampling period was July 1988-Dec. 1998. Basin. The Susquehanna River is 3 Sampling period was July 1989-Dec. 1998. the largest river draining to the 4 Sampling period was Oct. 1989-Dec. 1998. Bay and contributes about 60 percent of the total streamflow, 62 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 percent of the total nitrogen load, sample) was measured at the other stations. and 34 percent of the total phos- 6 Unadjusted concentration trends reported here are the same as flow-weighted concentration trends as phorus load from the nontidal part reported in Langland and others, 1999. of the Chesapeake Bay Basin.

4 The Susquehanna River (A) (B) drains parts of New York, EXPLANATION Pennsylvania, and Mary- Basin land, and includes some of Susquehanna the most productive agricul- Potomac tural land in the nation. James Agricultural activity is Rappahannock extensive in the lower Sus- Appomattox quehanna River Basin, con- Pamunkey tributing to the high yield of nitrogen (fig. 3). However, Mattaponi the phosphorus yield was Patuxent low, because phosphorus Choptank tends to bind to sediment Downward trend particles that settle to the No significant river bottom and become trend detected trapped behind Conowingo Dam (Langland and Hainly, 1997). The flow-adjusted con- Figure 5. Trends in flow-adjusted total nitrogen (A) and total phosphorus (B) concentrations in the centration of total nitrogen Chesapeake Bay Basin from the mid-to-late 1980’s through 1998. decreased about 12 to 25 percent at the Susquehanna River monitoring station during 1985-98 the total phosphorus load from the non- rus also were reduced. Because phospho- (fig. 4). The implementation of agricul- tidal part of the Chesapeake Bay Basin. rus tends to bind to sediment, the decrease tural and forestry BMP’s may be partly The Potomac River monitoring station, at in both phosphorus and suspended mate- responsible for the decrease in total nitro- Chain Bridge in Washington, D.C., rial (fig. 4) may indicate the effectiveness gen. The unadjusted concentration of total receives streamflow from 80 percent of of BMP’s aimed at controlling sediment nitrogen also decreased about 20 percent. the 14,670-mi2 Potomac River Basin. erosion. The success of these nutrient Trends in flow-adjusted and unadjusted Because the monitoring station lies control strategies on total phosphorus concentrations were comparable because upstream from the municipal wastewater concentration was offset by the increase there was no significant increase in flow discharges in the Metropolitan Washing- in flow, however, as the unadjusted total at this station during 1985-98 (fig. 7) to ton, D.C., area, water-quality characteris- phosphorus concentration did not offset the effects of nutrient control strate- tics and trends discussed in this report do decrease significantly. gies in the basin. not reflect contributions or changes in James River The flow-adjusted concentration of these wastewater discharges. total phosphorus decreased about 36 to 60 During the period 1985-98, the The James River monitoring station, at percent during the 14-year monitoring flow-adjusted concentration of total nitro- Cartersville, Va., receives streamflow period. Inputs from point sources, gen at the Potomac River monitoring sta- from about 60 percent of the 10,200-mi2 although not major contributors to the tion did not show a significant trend James River Basin. It is located upstream total phosphorus load at the Susquehanna (fig. 4), even though inputs from point from municipal wastewater discharges in River monitoring station, decreased by 56 sources of nitrogen above the station were the Richmond, Va., area. Of the nine riv- percent (Darrell and others, 1999). The reduced by about 10 percent during the ers monitored, it contributes about 12 per- decrease in phosphorus may be partly 14-year period (Darrell and others, 1999). cent of the streamflow, 5 percent of the attributed to the phosphate detergent ban The unadjusted concentration of total total nitrogen load, and 20 percent of the and to agricultural BMP’s. There was a 57 nitrogen also did not show a significant total phosphorus load, making it the third to 75 percent decrease in unadjusted total trend, even though streamflow increased largest nutrient and streamflow source phosphorus concentration. during that period (fig. 7). after the Susquehanna and the Potomac The flow-adjusted phosphorus con- Rivers. The James River Basin has the Potomac River centration decreased about 40 to 60 per- second largest yield of total phosphorus in The Potomac River is the second larg- cent during the 14-year period. Point the nontidal part of the Chesapeake Bay est river draining to the Bay and the sec- source inputs of phosphorus above the Basin (fig. 3). The relatively large phos- ond largest source of nitrogen and monitoring station were reduced by about phorus yield is caused by both point and phosphorus. It contributes about 20 per- 28 percent (Darrell and others, 1999), nonpoint sources, including wastewater cent of the total streamflow, 28 percent of largely due to the phosphate detergent treatment plants, high concentrations the total nitrogen load, and 33 percent of ban. Nonpoint source inputs of phospho- bound to sediment in agricultural runoff,

5 and naturally high concentrations from 3 percent of the total streamflow, 2 per- Any decrease in phosphorus concentra- soils and rocks. cent of the total nitrogen load, and 8 per- tion as a consequence of the phosphate A downward trend of about 44 to 69 cent of the total phosphorus load detergent ban probably would not have percent in the flow-adjusted concentration delivered annually from the nontidal part been evident because of the limited num- of total phosphorus was detected at the of the Chesapeake Bay Basin. The Rappa- ber of point sources in the basin upstream James River monitoring station during the hannock River Basin has the largest per- from the monitoring station. period 1988-98 (fig. 4). This downward centage of agricultural land among the The unadjusted concentrations of total trend was more evident in low-flow con- five monitored river basins in Virginia nitrogen and total phosphorus did not ditions than in high-flow conditions (Bell and the third largest of all nine basins change significantly during the 11-year and others, 1996), and most of the (table 3). Nonpoint sources contribute monitoring period, indicating that natural decrease occurred during 1988-90, soon more than 90 percent of the nutrient load streamflow variations and increasing after the phosphate detergent ban was in this basin, although a few point sources development in this basin may have offset implemented in Virginia. This suggests also are present. Steep slopes and abun- nutrient reductions resulting from the that point-source reductions were the dant pastureland in the basin cause the implementation of BMP’s. most effective nutrient control strategy in Rappahannock River to produce high Appomattox River this basin during the period monitored. yields of suspended material and the high- The unadjusted total phosphorus concen- est yield of total phosphorus (fig. 3). The Appomattox River monitoring tration decreased about 48 to 61 percent. The flow-adjusted concentrations of station, at Matoaca, Va., receives stream- During the 11-year monitoring period, total nitrogen and total phosphorus flow from approximately 84 percent of the flow-adjusted concentration of total decreased at the Rappahannock River the 1,600-mi2 Appomattox River Basin. nitrogen in the James River decreased monitoring station about 21 to 41 percent This river contributes about 2 percent of about 5 to 30 percent. With no significant and 41 to 76 percent, respectively, during the total streamflow, less than 1 percent of increase in streamflow (fig. 7) to offset the period 1988-98 (fig. 4). The imple- the total nitrogen load, and 1 percent of the effects of BMP’s, the unadjusted con- mentation of agricultural and forestry the total phosphorus load delivered annu- centration of total nitrogen also decreased BMP’s potentially was a major factor in ally from the nontidal part of the Chesa- about 4 to 34 percent. these trends. The Virginia Department of peake Bay Basin. Sediment with bound Conservation and Recreation estimates nutrients settles behind Lake Chesdin Rappahannock River that between 1985 and 1993 there was Dam, 2.8 miles upstream from the moni- The Rappahannock River monitoring about an 11 percent decrease in nitrogen toring station, contributing to the second station, upstream from Fredericksburg, and about an 18 percent decrease in phos- smallest yields of total phosphorus and Va., receives streamflow from about 57 phorus from nonpoint sources (Mark Ben- total nitrogen of the nine major basins percent of the 2,800-mi2 Rappahannock nett, Virginia Department of Conservation (fig 3). River Basin. This river contributes about and Recreation, written commun., 1996). Flow-adjusted total nitrogen concentrations decreased about 10 to 27 percent during the period (A) (B) 1989-98 (fig. 4). Unadjusted EXPLANATION total nitrogen concentrations Basin decreased about 14 to 22 per- Susquehanna cent. The similarity between Potomac these values results from a James lack of increase in streamflow Rappahannock during this period (fig. 7). The implementation of agri- Appomattox cultural BMP’s may be partly Pamunkey responsible for the decrease in Mattaponi total nitrogen. There were no Patuxent significant trends in either Choptank flow-adjusted or unadjusted Downward trend total phosphorus concentra-

No significant tions during the 10-year mon- trend detected itoring period. Because nonpoint sources contribute almost all of the nutrient load to the river, the phosphate detergent ban had little effect Figure 6. Trends in unadjusted total nitrogen (A) and total phosphorus (B) concentrations in the Ches- on phosphorus concentration apeake Bay Basin from the mid-to-late 1980’s through 1998. trends.

6 Pamunkey River during the 10-year mon- EXPLANATION The Pamunkey and Mattaponi Rivers itoring period. The simi- join below the Pamunkey River monitor- larity between these Basin ing station to form the York River, which values reflects the lack Susquehanna flows to Chesapeake Bay. The Pamunkey of a significant increase Potomac River monitoring station, near Hanover, in streamflow during James Va., receives streamflow from about 45 this period (fig. 7). Rappahannock 2 percent of the 2,400-mi York River Because of the small Appomattox Basin. The Pamunkey River contributes number of point sources Pamunkey about 2 percent of the total streamflow, in the Mattaponi River Mattaponi less than 1 percent of the total nitrogen Basin, the decreases in Patuxent load, and 2 percent of the total phospho- total nitrogen and total Choptank rus load delivered annually from the non- phosphorus concentra- tidal part of the Chesapeake Bay Basin. tions probably were Upward trend The basin has the third smallest yield of caused by changes in No significant trend detected total nitrogen and the fourth smallest nonpoint sources or yield of total phosphorus (fig. 3). The in-stream processes. basin is relatively flat, contains expanses of forested wetlands and marshes, and Patuxent River receives nutrients from both nonpoint and The Patuxent River Figure 7. Trends in streamflow (monthly mean discharge) in point sources, including agricultural run- monitoring station, in the Chesapeake Bay Basin from the mid-to-late 1980’s off and discharge from wastewater treat- Bowie, Md., receives through 1998. ment plants. streamflow from about No significant trends in flow-adjusted 37 percent of the 932-mi2 Patuxent River improvements. Unadjusted concentrations or unadjusted concentrations of total Basin. The basin lies completely within of total nitrogen also decreased about 63 nitrogen or total phosphorus were evident Maryland, between Baltimore and Wash- to 68 percent. at the Pamunkey River monitoring station ington, D.C., in an area of increasing The flow-adjusted concentration of during the period 1989-98 (fig. 4). urbanization. The Patuxent River contrib- total phosphorus decreased about 78 to 90 Mattaponi River utes less than 1 percent of the total percent during the 14-year monitoring streamflow, the total nitrogen load, and period (fig. 4). Inputs of phosphorus from The Mattaponi River monitoring sta- the total phosphorus load delivered annu- point sources were reduced by about 75 tion, near Beulahville, Va., receives ally from the nontidal part of the Chesa- percent during this period, largely due to streamflow from about 25 percent of the peake Bay Basin. Water quality is the phosphate detergent ban. Increased 2,400-mi2 York River Basin. The Mat- strongly affected by urban runoff and by streamflow (fig. 7) offset total phospho- taponi River contributes less than 1 per- eight wastewater treatment plants rus reductions more than total nitrogen cent of the total streamflow, the total upstream from the station. Because it is reductions, but the unadjusted total phos- nitrogen load, and the total phosphorus affected by relatively large number of phorus concentration still decreased about load delivered annually from the nontidal point sources, the Patuxent River has the 72 to 76 percent during the 14-year part of the Chesapeake Bay Basin. The highest median concentrations of total period. Mattaponi River Basin is relatively flat nitrogen and total phosphorus, as well as Choptank River and contains expanses of wetland areas. relatively large yields for both nutrients Because of the small area and low relief (fig. 3). The Choptank River monitoring sta- of this basin, the Mattaponi River has the The flow-adjusted concentration of tion, in Greensboro, Md., receives stream- second smallest annual load of both total total nitrogen decreased about 60 to 70 flow from about 14 percent of the 795-mi2 nitrogen and total phosphorus, after the percent during 1985-98 (fig. 4). Within Choptank River Basin. The Choptank Choptank River (fig. 3); however, yields the same period, point source inputs of River is the largest river on Maryland’s of total nitrogen and total phosphorus nitrogen were reduced by 53 percent Eastern Shore, but contributes less than 1 from the Mattaponi River are the small- (Darrell and others, 1999), largely as a percent of the streamflow, the total nitro- est. Nonpoint sources contribute most of result of implementation of biological gen load, and the total phosphorus load the nutrients to the river. nutrient removal at major wastewater delivered annually from the nontidal part Both flow-adjusted and unadjusted treatment plants between 1991 and 1993. of the Chesapeake Bay Basin. Land use in total nitrogen concentrations decreased Nutrient control strategies apparently the basin is primarily agricultural, pro- about 20 to 35 percent during the period have been particularly effective in this ducing the fourth largest yield of total 1989-1998 (fig. 4). Both flow-adjusted basin, as an increase in streamflow during nitrogen and the fifth largest yield of total and unadjusted total phosphorus concen- the 14-year period did not offset these phosphorus (fig. 3). trations decreased about 30 to 45 percent

7 For the period 1985-98, the SELECTED REFERENCES flow-adjusted concentration of total nitro- Bell, C.F., Belval, D.L., and Campbell, J.P., FOR MORE INFORMATION gen did not change significantly while the 1996, Trends in nutrients and suspended sol- unadjusted concentration of total nitrogen ids at the Fall Line of five tributaries to the For more information on USGS activi- decreased about 6 to 9 percent (fig. 4). Chesapeake Bay, Virginia, July 1988 The flow-adjusted concentration of total through June 1995: U.S. Geological Survey ties in Virginia and Maryland, please phosphorus decreased about 13 to 39 per- Water-Resources Investigations Report contact the following: cent during the 14-year period. This 96-4191, 37 p. decrease likely is a function of the District Chief approximately 50-percent decrease in the Darrell, L.C., Feit-Majedi, B., Lizarraga, J.S., U.S. Geological Survey flow-adjusted concentration of total sus- and Blomquist, J.D., 1999, Nutrient and sus- 1730 East Parham Road pended material (fig. 4). No known point pended-sediment concentrations, trends, Richmond, VA 23228 loads, and yields from the non-tidal part of sources of nutrients exist upstream of the Phone: 804-261-2600 the Susquehanna, Potomac, Patuxent, and or 800-684-1592 monitoring station on the Choptank Choptank Rivers, 1985-96: U.S. Geological River; therefore, these decreases are prob- Survey Water Resources Investigations District Chief ably due to nonpoint-source reductions. Report 98-4177, 39 p. The unadjusted total phosphorus concen- U.S. Geological Survey tration did not reflect the improvements Langland, M.J., and Hainly, R.A., 1997, 8987 Yellow Brick Road from these nutrient control strategies, as Changes in bottom-surface elevations in Baltimore, MD 21237 no significant decrease was detected. This three reservoirs on the lower Susquehanna Phone: 410-238-4200 was likely a result of increased stream- River, Pennsylvania and Maryland, follow- or 888-826-3130 flow during the monitoring period ing the January 1996 flood: Implications for (fig. 7). nutrient and sediment loads to the Chesa- Or visit our web sites at: peake Bay: U.S. Geological Survey http://va.water.usgs.gov/ WHAT PROGRESS IS BEING Water-Resources Investigations Report http://md.water.usgs.gov/ MADE TOWARD THE 97-4138, 34 p. 40-PERCENT NUTRIENT REDUCTION GOAL? Langland, M.J., Blomquist, J.D., Sprague, L.A., and Edwards, R.E., 1999, Trends and Additional information and data from Many of the major rivers draining to status of flow, nutrients, and sediments for the River Input Monitoring Program Chesapeake Bay are showing significant selected nontidal programs in the Chesa- can be found at: progress toward the goal of a 40-percent peake Bay Watershed, 1985-98: U.S. Geo- reduction in controllable nutrients man- logical Survey Open-File Report 99-451, http://va.water.usgs.gov/chesbay/RIMP/ dated by the Chesapeake Bay Agreement 64 p. in 1987. The effects of BMP’s are being observed across the Bay basin, but natural Maryland Department of Natural Resources, Information on USGS activities in the Maryland Department of Agriculture, Mary- increases in streamflow during the moni- Chesapeake Bay Region can be land Department of the Environment, Mary- found at: toring period have often counteracted land Office of Planning, and the University these improvements. In some rivers, how- of Maryland, 1999, Maryland’s tributary ever, significant reductions have not been teams: Annual Report 1998, 94 p. http://chesapeake.usgs.gov/chesbay/ achieved. As the States of Maryland, Pennsylva- Virginia Secretary of Natural Resources, Vir- nia, and Virginia, and the District of ginia Department of Conservation and Rec- Information on other Federal, State, Columbia assess their progress toward the reation, and Virginia Department of and Citizen Programs can be found on nutrient-reduction goal, they will imple- Environmental Quality, 1998, Third annual the EPA’s Chesapeake Bay Home ment tributary strategies for the nontidal report on the development and implementa- Page at: areas of Chesapeake Bay, including the tion of nutrient reduction strategies for Vir- ginia’s tributaries to the Chesapeake Bay, areas monitored by the River Input Moni- http://www.chesapeakebay.net/ 100 p. toring Program (Virginia Secretary of Natural Resources and others, 1998; Vogelmann, J.E., Sohl, T.L., Campbell, P.V., Maryland Department of Natural and Shaw, D.M., 1998, Regional land cover For more information on USGS ser- Resources and others, 1999). These strat- characterization using Landsat Thematic vices and products, call: egies contain specific plans for reducing Mapper data and ancillary data sources, nutrients in individual river basins, and Third EMAP Research Symposium, Albany, 1-888-ASK-USGS are expected to lead to substantial reduc- N.Y., April 8-11, 1997, Environmental Mon- tions in nutrients reaching Chesapeake itoring and Assessment, v. 51, p. 415-428. or visit the USGS Home Page at: Bay from its tributaries in coming years. By Donna L. Belval and http://www.usgs.gov/ Lori A. Sprague