corrosive effects. When water is to be supplied by underground wells, 

 the reservoir capacity must be known and withdrawal controlled to avoid 

 excessive losses from groundwater supplies. The lowering of the water 

 table could cause land subsidence or induce saltwater intrusion into 

 the groundwater system in estuarine and oceanic areas. 



4.15.3 Discharge Design and Operation 



Heated effluent may adversely affect the natural patterns of life and 

 the behavior of aquatic species. How pervasive this thermal pollution may 

 be and how damaging depends on the temperature, volume of output, and size 

 and flushing characteristics of the water basin. Thermal discharges can 

 alter the chemical nature of receiving waters in many ways. Solubility 

 of dissolved oxygen, toxicity of heavy metals, and metabolic rates of 

 aquatic organisms are affected by changes in water temperatures [7]. In- 

 jury to organisms is dependent upon a variety of actors, including ambient 

 water temperature, biocide dosage, previous thermal history, physiological 

 state, organism size and life stage. 



The influence of heat on the stationary elements of the ecosystem 

 is often far simpler to detect than that of mobile elements. Studies 

 on aquatic animal and plant life have typically shown adverse effects 

 in the vicinity of the discharge plumes of plants with open-cycle cooling. 

 Thermal pollution from industrial cooling discharge is not so much the 

 leading cause of damage to aquatic ecosystems as was once believed. If 

 the heat builds up in a confined area of water, one can expect localized 

 loss of life which may be accelerated in summer by thermal shock and the 

 synergizing effect of temperature on mechanical or chemical factors. 

 The following general guidelines are applicable to estuaries of the Mid 

 Atlantic [138]: 



Discharge 



Temperature (F) Effect on Zooplankton 



80 Death or damage to a high proportion 



of the more sensitive species. 



85 Mortality and high damage to more 



sensitive species; significant but 

 lower for more resistant species. 



90 Widespread high mortality and damage 



to all but the more resistant species. 



95 Nearly complete mortality among most 



species. 



171 



