the sediments return much of their nutrient burden to the aquatic systems, but a 

 portion remains in the long-term sink. 



Only limited and comparatively trivial efforts are yet underway to recapture 

 nutrients and use them advantageously, despite the abundance of soil in the region 

 impoverished by long cultivation of corn and tobacco. 



Efforts to model and budget the nutrient sequence in the Chesapeake and its tribu- 

 taries have been progressive and promise value in management. Among them: 



• A two-dimensional quasi-linearized steady-state model of nutrient-phytoplank- 

 ton interactions in the upper Bay was constructed to guide allocations (Hydro- 

 science, Inc., 1975). It indicates that phosphorus is thecontrolling nutrient above 

 the Potomac and that the primary nutrient sources are the Baltimore 

 metropolitan area and the Susquehanna River. Much of the introduced nutrient 

 is retained in sediments near the source. 



• A one-dimensional tidal-time model was employed. Its purpose was to assist esti- 

 mation of the environmental effects resulting from complete implementation of 

 the Water Quality Control Act of 1972 and its amendments (Kuo et al., 1975). 



• Applying model results to projection of biological impacts from changing the 

 loading of nutrients and from oxygen-demanding pollutants yielded estimates. 

 But this application also demonstrated the overwhelming complexity of such 

 efforts (Roberts et al., 1975). 



• From elementary raw data, a mass balance nutrient budget for the total Chesa- 

 peake Bay was constructed on a monthly basis (Laniak, 1979). Yearly loadings of 

 nitrogen and phosphorus from point sources (the principal source of phospho- 

 rus), the tributaries (principal for nitrogen), and the air were estimated, as were 

 outputs by advection and ocean loss. Seventy percent of the 1,212 X 10 s kg/yr 

 (2,666 X 10' lb/ yr) of total nitrogen received and 99 percent of the 164 X 10 s kg/yr 

 (360 X 10" lb/yr) of total phosphorus apparently remain in the Bay. Substantial 

 seasonal variation occurs. The results are interpreted in relation to adequate 

 monitoring of nutrient-related materials and processes. 



• A major analysis of the sources of nutrients and the scale of "eutrophication" 

 problems in estuaries included, among others, consideration of the external 

 budget of the Chesapeake (Jaworski, in press). In 1971, 41,400 kg day (91.080 

 lb day) of phosphorus (69 percent from wastewater discharges) and 297,900 

 kg/ day (655,380 lb day) of nitrogen (68 percent from upper basin land runoff) 

 entered the system. Variation between months and years, changes in the forms of 

 nitrogen and phosphorus, and the gradients with distance downstream are dis- 

 cussed and related to a suggested scale of"eutrophication"and related to parts of 

 the Bay and the total system. 



From its inception, the Environmental Protection Agency's Chesapeake Bay 

 Program has recognized and emphasized the importance of excessive nutrients in the 

 Bay system. Under the inappropriate term "eutrophication" it has arranged for an 

 important and valuable series of studies and research projects. None of the final 

 reports are yet available, but the studies include (Wells et al., 1979 and Davies, 1980): 



• Definition of Chesapeake Bay Problems of Excessive Enrichment or Eutrophi- 



cation 



• An Assessment on Nonpoint Source Discharge, Pequea Creek Basin, Lancaster 



County. Pennsylvania 



• Evaluation of Water Quality Management Tools in the Chester River Basin 



• Intensive Watershed Study (Patuxent River Basin) 



• Evaluation of Management Tools in Two Chesapeake Bay Watersheds in 



Virginia 



• Modeling Philosophy and Approach for Chesapeake Bay Program Watershed 



Studies 



• Fall Line Monitoring of the Potomac, Susquehanna, and James Rivers 



• Assessment of Nutrients from Various Sources 



26 



