• Land Use and Point Source Nutrient Loading in the Chesapeake Bay Region 



• Chesapeake Bay Circulation Model 



• Water Quality Laboratory for Chesapeake Bay and Its Subestuaries at Hampton 



Institute 



• Chesapeake Bay Nutrient Dynamics 



• Chesapeake Bay Circulation and Water Quality Mathematical Models (two 



projects) 



• Development of Assessment Tool to Evaluate Nutrient Transport and Fate in the 



Lower Susquehanna River 



• Intensive Watershed Study (Chester River Basin) 



• A Water Quality Modeling Study of the Chesapeake Bay Watersheds. 



Growth in understanding and in the ability to manage nutrients rationally in the 

 Chesapeake Bay region will be substantial. Since the population is predicted to 

 double within about 40 years — with probable further subsequent increases — the 

 need for adequate knowledge and effective management remains urgent. 



Sediments 



As in every estuary, there is continuous input of materials that become sediments. 

 These arise from transport from the total basin by river water, from erosion of 

 shores, from the products of biological activity, and, in some cases, from the sea. 

 Sediments are deleterious to uses through filling of channels, progressive deposition 

 in headwater areas, interference with light penetration, and smothering of benthic 

 biota. Smothering is an occasionally serious event (Chesapeake Research 

 Consortium, 1976), and reduced light penetration is under evaluation as a 

 contributor to the extensive diminution of submerged aquatic vegetation over much 

 of Chesapeake Bay since 1971 (Stevenson and Confer, 1978). 



Inputs into the Chesapeake system are not precisely known, but the main stem of 

 the Bay has been estimated to receive about 1.07 X 10 6 tons per year from the Sus- 

 quehanna, .60 X 10 6 tons from shoreline erosion, an unknown quantity from bio- 

 logical sources, and about .20 X 10 6 tons from the ocean (Schubel and Carter, 1976). 

 The large tributaries are sinks for their own materials, and part of the Bay load 

 moves into them. The Bay is filling at an average rate of about .8 mm/year — about 

 3.5 to 4.0 mm/ year at its head (Schubel and Carter, 1976). The reservoirs of the Sus- 

 quehanna River dams were long considered to be sinks, but Tropical Storm Agnes 

 flushed much of the accumulation in 3 days (Chesapeake Research Consortium, 

 1976). 



The contribution of human activity to the input, dispersion, deposition, and resus- 

 pension and redeposition of sediments is not clear. In general, land clearing for agri- 

 culture or construction increases riverine input. Excessive nutrients increase plank- 

 ton biological production, and wakes from ships and boats add to natural shoreline 

 erosion. Particulate industrial wastes and urban runoff add sediments, and upland 

 alterations that modify the "flashiness" of river flow will affect the sediment input 

 and distribution. These have not been quantified for this estuary, but some of these 

 human effects have been discussed (Schubel and Williams, 1976; Schubel and Wise, 

 |979). 



The most important problems related to sediments are those associated with the 

 continuous and external filling of channels where shipping or boating is desired and 

 with the remarkable affinity of sediments for chemicals. Sediments have long been 

 recognized as the source of large-scale economic and, more recently, environmental 

 problems in the Chesapeake Bay region, where major cities (Baltimore, Washington. 

 Richmond) lie on the fall line, above sites of natural deposition (Federal Water 

 Pollution Control Administration, 1969). Channels must be wide and deep enough 

 for shipping, and the beam, depth, and number of ships continue to increase (Villa et 

 al., 1977). Maintenance of depths is a cost of pollution to the degree that the 

 accumulating sediments result from human activities. In the Chesapeake, present 

 channels require maintenance dredging of about 7,600,000 m\ yr (10,000,000 



27 



