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| MD-DE-DC Water Science Center |
U.S. GEOLOGICAL SURVEY
Scientific Investigation Report 2004-5125
Excess nutrient and sediment loads in the Chesapeake Bay can cause unbalanced water-quality conditions that reduce the amount of oxygen and sunlight available to aquatic plants and organisms. Nutrient and sediment loads and trends were analyzed at four nontidal tributaries in the Chesapeake Bay watershed to collect additional data for the ongoing (since 1985) U.S. Geological Survey Chesapeake Bay River Input Monitoring Program. These sites were Chesterville Branch in Maryland, Conodoguinet Creek in Pennsylvania, North Fork Shenandoah River in Virginia, and South Fork Shenandoah River in Virginia. Monthly base-flow and stormflow water-quality samples were collected at each site, with a total of 90–120 samples collected at each site during the study period (1997–2001). These data were used to compute annual and monthly loads for selected nutrient and suspended-sediment constituents using a mass-load estimating model, ESTIMATOR, developed by the U.S. Geological Survey. Each of the four study sites in this report was characterized on the basis of land use and water-quality data. Basins with high percentages of agricultural land use had higher nitrogen and phosphorus loads and yields than basins with higher percentages of forested land and less agricultural land. No relation between land use and suspended-sediment loads and yields was evident. Study results also indicate that suspended-sediment loads were higher in years of high mean annual streamflow at Conodoguinet Creek, North Fork Shenandoah River, and South Fork Shenandoah River. The highest total suspended-sediment loads and yields at Chesterville Branch were caused by Hurricane Floyd in 1999, which was not a year with the highest annual total streamflow. Results of this study indicate that a 5-year period of record is too short a timeframe to characterize factors affecting trends. Moreover, a combination of extreme variability in climate and lack of recent land-use data made characterizing basin nutrient and sediment relations problematic. Although the data and analysis established a baseline of water quality at the four tributaries, additional monitoring and tracking of loads would help identify long-term trends and factors affecting trends.
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Abstract
Introduction
Background
Purpose and scope
Previous studies
Acknowledgments
Description of study sites
Chesterville Branch near Crumpton, Maryland
Conodoguinet Creek near Hogestown, Pennsylvania
North Fork Shenandoah River near Strasburg, Virginia
South Fork Shenandoah River at Front Royal, Virginia
Methods of study
Data collection
Measurement of streamflow
Water-quality samples
Collection technique and equipment
Sample processing and analysis
Quality-assurance program
Data analysis
Estimation of loads
Calculation of trends
Concentrations, loads, and trends at study sites
Concentrations of nutrients and suspended sediment
Chesterville Branch
Conodoguinet Creek
North Fork Shenandoah River
South Fork Shenandoah River
Loads of nutrients and suspended sediment
Chesterville Branch
Conodoguinet Creek
North Fork Shenandoah River
South Fork Shenandoah River
Trends of nutrients and suspended sediment
Chesterville Branch
Conodoguinet Creek
North Fork Shenandoah River
South Fork Shenandoah River
Comparison of study sites
Summary and conclusions
References cited
Appendix A
Appendix B
1–3. Maps showing:
1. Location of Chesapeake Bay watershed study area, study site basins, and Chesapeake Bay River Input Monitoring Program site basins
2. Location of Chesapeake Bay watershed study area showing land-use percentages of study site basins
3. Hydrogeomorphic regions in the Chesapeake Bay watershed
4–5. Photographs showing:
4. Stainless-steel weighted-bottle sampler and hand-reel with polyethylene rope
5. DH-95 isokinetic sampler with 1-liter Teflon bottle
6. Boxplots showing range of concentrations of (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at study sites
7–10. Graphs showing:
7. Daily mean discharge and observed concentrations for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at Chesterville Branch near Crumpton, Maryland, January 1997 through December 2001
8. Daily mean discharge and observed concentrations for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at Conodoguinet Creek near Hogestown, Pennsylvania, January 1997 through December 2001
9. Daily mean discharge and observed concentrations for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at North Fork Shenandoah River near Strasburg, Virginia, January 1997 through December 2001
10. Daily mean discharge and observed concentrations for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at South Fork Shenandoah River at Front Royal, Virginia, January 1997 through December 2001
11–12: Bar charts showing:
11. Mean annual streamflow at study sites, 1997–2001
12. Calculated yields for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment at study sites, 1997–2001
13–15: Plots showing:
13. Comparison of average annual yields for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment and percentage of agricultural land use at the study sites and River Input Monitoring Program sites, 1997–2001
14. Comparison of average annual yields for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment and percentage of forested land use at the study sites and River Input Monitoring Program sites, 1997–2001
15. Comparison of average annual yields for (A) total nitrogen, (B) total phosphorus, and (C) suspended sediment and percentage of developed land use at the study sites and River Input Monitoring Program sites, 1997–2001
1. Study site locations and land-use characteristics in the study basins, Chesapeake Bay watershed
2. Constituents and field parameters monitored at study sites in the Cheapeake Bay watershed, 1997–2001
3. Summary statistics for selected water-quality constituents monitored at the study sites in the Chesapeake Bay watershed, 1997–2001
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For more information about USGS activities in Maryland, Delaware, and the District of Columbia, contact:
Director
MD-DE-DC Water Science Center
U.S. Geological Survey
8987 Yellow Brick Road
Baltimore, MD 21237
Telephone: (410) 238-4200
or access the USGS Water Resources of Maryland, Delaware, and District of Columbia home page at: http://md.water.usgs.gov/.
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