234 



accompanying stresses both on the natural assimilative capacities of 

 these estuaries and the biofcic communities presently existing there. 

 Pressures for increased upstream diversion and use of fresh water 

 are certain to increase in all biophysical regions, but the relatively 

 arid and high-growth western gulf and the Southwest Pacific coasts 

 are projected to experience the greatest pressures on present estuarine 

 systems for at least three main reasons : 



(1) Much of the upstream water is used to support irrigation 

 with accompanying actual loss of water to the inflow systems by 

 evaporation, transpiration, and absorption, as well as mineraliza- 

 tion through leaching. 



(2) The amount of rainfall and snow pack is highly variable 

 and often results in extended periods of flooding and drought in 

 these regions. 



(3) Consumption of water other than for irrigation is bound 

 to increase at a high rate in response to expected population growth 

 considerably above the national average. 



It should be noted, however, that these diversion projects may also 

 allow increased control of water inflows that could be beneficial to 

 maintenance of existing estuarine productivity. Furthermore, some 

 proposed projects may merely shift the major portion of existing in- 

 flows from one area to another as in the case of the proposed diversion 

 of Delaware River inflow from Delaware Bay, through the Hudson 

 River, to Raritan Bay, and New York Harbor. 



Municipal wastes 



Municipal waste water disposal is the most frequently cited example 

 of water quality degradation. The major impact of municipal waste 

 water discharge is calculated on the basis of the amount of biological 

 oxygen demand (BOD), bacterial indicator organisms, generally coli- 

 forms, and suspended and dissolved solids reaching both fresh and 

 estuarine water. The magnitude of the future extent of the water pollu- 

 tion problem is indicated by the projection that, even if secondary 

 treatment were provided for all urban and sewered population in the 

 United States by 1980, the amount of residual wastes reaching the Na- 

 tion's waters would be about the same as today when much of this popu- 

 lation is not served by secondary treatment facilities. From approxi- 

 mate coefficients developed by the Federal Water Pollution Control 

 Administration for municipal wastes generated by man in areas served 

 by sewers, a rough estimate of the overall yearly municipal sewered 

 waste loads may be computed for the estuarine zone as shown in 

 table IV.4.9. 



TABLE IV.4.9.— APPROXIMATE MUNICIPAL WASTES GENERATED YEARLY BY THE ESTUARINE ZONE POPULATION, 



1960-80 



Note: These projections are based on formulae found in the FWPCA publication. The Cost of Clean Water, Vol. II, "De- 

 tailed Analysis" (Washington, D.C.: U.S. Government Printing Office, 1968), p. 68. 



