Therefore, the entire picture of change is quite clear, the flora and fauna 

 disappear. 



The disappearance of valuable commercial species (which are usually 

 sensitive to chemical pollution) has been described for some time in the 

 literature. However, the scale of pollution and the variety of pollutants 

 have increased greatly in the present century and particularly since the 

 1940s. Therefore, maintenance of reservoirs in a state desirable for man 

 has become much more difficult. 



We must see clearly that the struggle for pure water of good quality and 

 containing valuable organisms is a difficult task, a long-term task requir- 

 ing significant effort of the entire state and of intergovernmental organi- 

 zations as well . 



In terms of preservation of hydrobiologic processes in reservoirs, which 

 assure the required quality of water and productivity of commercial species, 

 we must limit the arrival of toxic substances into bodies of water. Of 

 course, it would be quite good if we could completely eliminate any pollu- 

 tion (from the atmosphere, soil, waste and flood waters), but this is un- 

 realistic, at least for the foreseeable future. Therefore, regulation and 

 protection of reservoirs from toxic substances is a task of primary impor- 

 tance. 



In developing specific indexes to be used to limit toxins, it is usually 

 noted that, if a reservoir has a capacity for self-purification, it should 

 be used, or allowed to purify all the discharge dumped into the reservoir. 

 It is said that this is quite economical. This means of solution of the 

 problem is quite favorable to the industry doing the polluting, but not to 

 the nation, since other water users will be restricted or even denied the 

 ability to use the polluted water. Our laws and constitution note that na- 

 tural waters belong to the state and are used in a combined matter, i.e., by 

 various water usei^s. 



Yet another suggestion has been heard to ease the burden on industry. 

 Before waste waters are dumped into a reservoir, they should be diluted with 

 pure water, thus accelerating self-purification of the water. Actually, as 

 the concentration of organic substances and toxins decreases, the rate of 

 self-purification increases. However, from where is this pure water to be 

 taken for dilution at a time when the water consumption of industry is great 

 and increasing rapidly? Furthermore, studies which we have performed show 

 that the wastewaters of some chemical combines would have to be diluted by a 

 factor of 200-500 to eliminate their toxicity (Stroganov, et al^. 1978). 

 There is not enough pure water for this purpose, and the waTer, which would 

 be used, is not completely pure. Therefore, even the water in the deltas of 

 large rivers is not completely pure, not completely suitable for drinking 

 and fishing purposes. What is the answer? 



The only effective answer to this problem is to decrease the quantity of 

 toxins entering bodies of water. The achievements of science and tech- 

 nology, all technical progress, allow this to be done, but economic diffi- 

 culties arise. The techniques needed to decrease the concentration on 



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