Skip Links

USGS - science for a changing world

Scientific Investigations Report 2012–5185

Flux of Nitrogen, Phosphorus, and Suspended Sediment from the Susquehanna River Basin to the Chesapeake Bay during Tropical Storm Lee, September 2011, as an Indicator of the Effects of Reservoir Sedimentation on Water Quality

By Robert M. Hirsch

Thumbnail of and link to report PDF (2.43 MB)

Abstract

Concentrations of nitrogen, phosphorus, and suspended sediment are measured at the U.S. Geological Survey streamgage at Conowingo Dam at the downstream end of the Susquehanna River Basin in Maryland, where the river flows into the Chesapeake Bay. During the period September 7–15, 2011, in the aftermath of Tropical Storm Lee, concentrations of these three constituents were among the highest ever measured at this site. These measurements indicate that sediment-storage processes behind the three dams on the lower Susquehanna River are evolving. In particular, they indicate that scouring of sediment (and the nitrogen and phosphorus attached to that sediment) may be increasing with time. Trends in flow-normalized fluxes at the Susquehanna River at Conowingo, Maryland, streamgage during 1996–2011 indicate a 3.2-percent decrease in total nitrogen, but a 55-percent increase in total phosphorus and a 97-percent increase in suspended sediment. These large increases in the flux of phosphorus and sediment from the Susquehanna River to the Chesapeake Bay have occurred despite reductions in the fluxes of these constituents from the Susquehanna River watershed upstream from the reservoirs. Although the Tropical Storm Lee flood event contributed about 1.8 percent of the total streamflow from the Susquehanna River to the Chesapeake Bay over the past decade (water years 2002–11), it contributed about 5 percent of the nitrogen, 22 percent of the phosphorus, and 39 percent of the suspended sediment during the same period. These results highlight the importance of brief high-flow events in releasing nitrogen, phosphorus, and sediment derived from the Susquehanna River watershed and stored in the Conowingo Reservoir to the Chesapeake Bay.

First posted August 30, 2012

For additional information contact:
Robert Hirsch
Research Hydrologist
U.S. Geological Survey
12201 Sunrise Valley Drive
Reston, VA 20192
Email: rhirsch@usgs.gov
http://chesapeake.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Hirsch, R.M., 2012, Flux of nitrogen, phosphorus, and suspended sediment from the Susquehanna River Basin to the Chesapeake Bay during Tropical Storm Lee, September 2011, as an indicator of the effects of reservoir sedimentation on water quality: U.S. Geological Survey Scientific Investigations Report 2012–5185, 17 p.



Contents

Abstract

Introduction

Nitrogen

Total Phosphorus

Suspended Sediment

Overview of Tropical Storm Lee Fluxes for the Susquehanna River at Conowingo, Maryland

Implications for the Chesapeake Bay

Summary and Conclusions

Acknowledgments

References Cited

Appendix 1. Daily-mean discharge, average flux, and flow-normalized annual flux values from the Weighted Regressions on Time, Discharge, and Season (WRTDS) model for total nitrogen in the Susquehanna River at Conowingo, Maryland, water years 1978–2011

Appendix 2. Daily-mean discharge, average flux, and flow-normalized annual flux values from the Weighted Regressions on Time, Discharge, and Season (WRTDS) model for total phosphorus in the Susquehanna River at Conowingo, Maryland, water years 1978–2011

Appendix 3. Daily-mean discharge, average flux, and flow-normalized annual flux values from the Weighted Regressions on Time, Discharge, and Season (WRTDS) model for suspended sediment in the Susquehanna River at Conowingo, Maryland, water years 1978–2011


Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://pubs.usgs.gov/sir/2012/5185/
Page Contact Information: GS Pubs Web Contact
Page Last Modified: Thursday, January 10, 2013, 07:59:15 PM