of water in reservoirs. It seems that theoretical problems of water 

 toxicology should be solved in the aspect of development of principles. 



In estimating the qualitative state of a reservoir, one can obtain 

 varying answers, depending on our requirements, i.e., the initial stand- 

 point. Among the many water users, the highest demands for water quality 

 are those of but two: fishermen and those who drink the water. Therefore, 

 all of the questions which are stated can be answered in terms of satis- 

 faction in the reservoir of the condition of high productivity of commercial 

 species and good quality of drinking water. If these standards are met, we 

 must call this body of water a normal one; if they are not met, it must be 

 considered an anomalous or even pathologic body of water. This last term is 

 used by hydrobiologists, although it is not really quite applicable to 

 bodies of water. 



As the economy becomes increasingly industrialized and "chemicalized", a 

 situation arises in which the need for fresh water of good quality increases 

 greatly, both for various branches of the economy and for water supply for 

 the population. However, the quality of fresh water is continually reduced, 

 a situation which has led to great difficulties in water supply. 



The Soviet Union has tremendous reserves of fresh water, but their dis- 

 tribution does not correspond to the needs of the regions with the greatest 

 concentration of industrial entities, agriculture and other branches of the 

 economy. Redistribution of fresh water over the territory of the country is 

 quite expensive, and furthermore has great effects on the ecology of large 

 areas. Therefore, various steps must be taken to preserve good quality of 

 fresh water (purification of industrial wastes, improvement of the tech- 

 nology of production in order to decrease the consumption of water and 

 dumping of wastewater into reservoirs, transition to closed cycles and dry 

 technologies). In order to preserve the water quality which is needed, it 

 is necessary to first of all limit the discharge of pollutants into reser- 

 voirs, i.e., standardize or regulate the discharge of chemical pollutants. 



Various indexes characterize the level of pollution in water: chemical, 

 bacteriologic, hydrobiologic and the MPC's for individual toxins. The 

 chemical and biologic factors are the most widely used, the MPC's being less 

 frequently used and hydrobiologic indexes being quite rarely used. However, 

 it is hydrobiologic processes in reservoirs which play the decisive role in 

 the formation of water quality. Aquatic organisms, on the one hand, develop 

 their vital activity on the basis of hydrochemical and hydrologic modes; 

 water for their habitation and, on the other hand, the predominance of 

 various species of aquatic organisms determines the direction of hydro- 

 biologic processes and thereby determines the nature of formation of water 

 quality. 



This interrelationship of water quality and hydrobiologic processes in a 

 reservoir causes definite difficulties in standardization of the discharge 

 of chemical pollutants into reservoirs and in the production of water qual- 

 ity. The necessity has arisen for indicating hydrologic principles which 

 must form the basis for development of standards for the protection of good 

 water quality, and for estimation of normal and pathologic states of reser- 



20 



