ASSESSMENT METHODOLOGIES FOR FRESHWATER INFLOWS 

 TO CHESAPEAKE BAY 



C. John Klein, Owen P. Bricker, David A. Flemer, Thomas H. Pheiffer, 

 James T. Smullen, and Richard E. Purdy 



Environmental Protection Agency, Annapolis, Maryland 



ABSTRACT 



The U.S. Environmental Protec- 

 tion Agency (EPA) Chesapeake Bay 

 program is conducting an in-depth 

 study to assess the principal factors 

 having adverse impacts on the water 

 quality of the bay. The program fo- 

 cuses on the point and nonpoint 

 sources of pollution including nu- 

 trients and toxic chemicals that are 

 associated with various land use 

 practices. Water quality data will 

 be evaluated through use of stochas- 

 tic and deterministic models. 



Field data collected on specific 

 land uses from five test basins will 

 be the basis for research to verify 

 nonpoint source runoff rates. The 

 field data will be used to calibrate 

 and verify mathematical models in the 

 test basins including nonpoint 

 source loading, stream transport and 

 estuarine processes. In particular, 

 the estuarine models will simulate 

 the impacts of nutrients on water 

 quality. Fall line water quality 

 data will serve as an independent 

 data set to compare the point and 

 nonpoint source projections associ- 

 ated with various land use activi- 

 ties . 



Mathematical models will be 

 employed on a bay-wide scale to gene- 

 rate nonpoint source loadings basin- 

 wide and to assess the impact from 

 those loading on the tidal bay for 

 the present (1980) and future (2000) 

 conditions. Several growth scenarios 

 that include consumptive freshwater 



use will be evaluated for their im- 

 pact on water quality in the bay. 



INTRODUCTION 



The Chesapeake Bay is one of the 

 largest estuarine complexes in North 

 America. It is a moderately strati- 

 fied system exhibiting temporally and 

 spatially complex hydrodynamics in 

 both the vertical and the horizontal 

 directions (Pritchard 1967). The 

 bay is 195 miles long with 8,000 

 miles of shoreline, a surface area of 

 (tidal estuarine system) about 4,300 

 square miles and a drainage basin of 

 64,000 square miles. The bay re- 

 ceives drainage water from six states 

 with the major supply contributed by 

 the states of Pennsylvania, Maryland 

 and Virginia (Figure 1). The Susque- 

 hanna River supplies about 50 percent 

 of the annual freshwater supply with 

 the Potomac and James Rivers account- 

 ing for another 35 percent. 



Because of the bay's size, its 

 wealth of natural and economic re- 

 sources and the need for a continued 

 stewardship, the U.S. Environmental 

 Protection Agency was authorized in 

 1976 to initiate the Chesapeake Bay 

 Program. The program is a five-year 

 study of the environmental quality 

 and resources management of the bay. 

 From a list of 10 candidate problem 

 areas, the program initially under- 

 took work in three technical areas; 

 (1) toxic chemicals in the food 

 chain, (2) eutrophication (the supply 



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