processes . 



The population of the Chesapeake 

 Bay Region is expected to nearly 

 double in the next 50 years. The 

 majority of these people will prob- 

 ably be served by central water sup- 

 ply systems and it has been demon- 

 strated that a typical community will 

 return to a stream only 75 to 90 per- 

 cent of the water withdrawn from it. 

 It is possible that none of the water 

 would be returned if an inter-basin 

 transfer is involved. 



An increasing population needs 

 more food. Because of limited land 

 resources and economic factors it 

 will probably be necessary to sub- 

 stantially increase irrigation prac- 

 tices. Almost all of the water used 

 for this purpose never returns to the 

 system or takes so long to return 

 that, for all practical purposes, it 

 is considered lost. 



As economic activity expands, 

 more water will be needed for in- 

 dustrial processes. This alone would 

 result in a substantial increase in 

 consumptive use. There is, however, 

 a definite trend toward an increased 

 use of processes such as cooling 

 towers, which involve the evaporation 

 of water. The consumptive use of 

 water associated with this is often 

 markedly greater than some other 

 types of processes. 



Nearly every tributary to Chesa- 

 peake Bay will be subjected to the 

 consequences of increased consumptive 

 uses of water. Table 1 has been pre- 

 pared in order to assist in placing 

 the magnitude of these uses in per- 

 spective. Shown on this table are 

 the actual discharges of the Susque- 

 hanna River during August, September, 

 and October of the drought year 1964, 

 the anticipated consumptive uses of 



water in the year 2020, and the con- 

 sequential reduced freshwater in- 

 flows. These reduced inflows have 

 been adjusted to reflect the influ- 

 ences of several dams which have 

 been constructed since 1964 and, 

 where appropriate, the discharges 

 from wastewater treatment plants. 



Under low flow conditions these 

 consumptive uses often constitute a 

 considerable portion of the natural 

 flow in a river. For instance, the 

 losses in the Susquehanna River dur- 

 ing this dry period constitute from 

 24 percent to 66 percent of the na- 

 tural river flow. Similarly, in the 

 Potomac River, consumptive losses are 

 from 40 percent to 70 percent and in 

 the James River 11 percent to 36 per- 

 cent of the natural river low flow. 



During periods of higher flows, 

 the consumptive uses are only a small 

 fraction of the total river flow. On 

 the average, consumptive uses consti- 

 tute 4 percent of the 39,000 cfs 

 average flow in the Susquehanna Riv- 

 er, 6 percent of the 7,900 cfs aver- 

 age flow in the James River, 7 per- 

 cent of the 11,000 cfs average flow 

 in the Potomac River and 5 percent of 

 the 76,600 cfs average contribution 

 of fresh water by all tributaries to 

 the bay. 



There is widespread concern 

 relative to the potential consequen- 

 ces of these reduced freshwater in- 

 flows. The Susquehanna River Basin 

 Report Coordinating Committee in its 

 1969 report identified this as a high 

 priority study item and both the 

 Susquehanna River Basin Commission 

 and the State of Maryland have 

 written to the Baltimore District 

 Engineer requesting that the Corps of 

 Engineers perform studies addressing 

 the problem. In addition, the Chesa- 

 peake Bay Study Advisory Group, 



117 



