of fishing and drinking water supply. Only a few industries require water 

 containing \jery low contents of salts. Such water users perform special 

 water preparation measures on the water taken from the reservoir. There- 

 fore, priority in the use of water is quite significant in the protection 

 of water. In our water law it is noted that priority in the use of water 

 must be given to organizations supplying water for drinking purposes and to 

 fishing. Evaluations of the quality of the water and testing of water are 

 performed by the Health Ministry and the Fishing Industry Ministry. This 

 principle essentially lies at the basis of our water law, adopted in 

 December 1970 (see sections 10, 15, 28, 31 and 37). Considering the great 

 sensitivity of many species to chemical pollution, the formation of pure 

 water of good quality by various species of aquatic organisms, and also con- 

 sidering the high sensitivity of valuable commercial species (fish, crabs, 

 mollusks), priority should be given first of all to the fishing industry, 

 with all of the results which follow from this (evaluation of water quality, 

 testing and development of quality standards of discharge, etc.). 



2. The principle of sufficient self-purification. This important 

 principle is the basis of all subsequent principles. It means that all of 

 the chemical pollutants which enter a reservoir must be mineralized to 

 limits of concentration such that the species forming pure water of good 

 quality and the species which are valuable commercial organisms can con- 

 tinue to exist. This means that for each region, climatic zone, the upper 

 limit of self -purifying capacity of the water of a reservoir, which must not 

 be exceeded, is the point of introduction of a greater quantity of pollu- 

 tants than the body of water can process. Increasing the load of chemical 

 pollution on a body of water above the limit of its self-purifying capacity 

 leads to disruption of the principle of sufficient self-purification, lead- 

 ing to pollution of the body of water and degradation of the entire ecologic 

 water system. 



Processes of self -purification always occur (Figure 4), but not always 

 with sufficient speed and completeness to assure the subsequent principles 

 (i.e., 3 and 4). Therefore, self -purification may be sufficient for insen- 

 sitive commercial species, but not sufficient for highly sensitive species 

 and not sufficient to assure good quality of drinking water (principle 4). 

 Consequently, the sufficiency of self-purification is evaluated on the basis 

 of principle 1 (priority). For some water users, the requirements for water 

 purity are lower and they may be satisfied with incomplete pur.if ication of 

 water. Fishing and drinking water supply require water of the highest 

 purity. Each water user can establish his own level of sufficiency of self- 

 purification. We shall analyze it on the basis of the priority indicated 

 earlier. 



The quantitative indicators used to evaluate sufficient self-purifica- 

 tion cannot be limited to BOD, COD AND O2 content. Since we must always ex- 

 pect toxins to be present in water, we must determine the rate of processes 

 of nitrification in both phases. As was noted earlier (Stroganov 1978), 

 toxins decrease the rates of these processes, thus delaying the time of suf- 

 ficient purification. In addition to these indexes, we must also have in- 

 formation on the toxicity of water for organisms. In most cases, nitrify- 

 ing organisms are more sensitive to toxins than are saprophytes, while most 



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