Growth of the population, expansion old and emergence of the new cities considerably increased receipt of household drains in internal reservoirs. These drains became a source of pollution of the rivers and lakes pathogenic bacteria and helminths. In even bigger degree pollute reservoirs the washing synthetic means which are widely used in life. They find broad application also in the industry and agriculture. The chemicals containing in them, coming with sewage to the rivers and lakes, have considerable impact on the biological and physical mode of reservoirs. As a result ability of waters to saturation by oxygen decreases, activity of the bacteria mineralizing organic substances will be paralyzed.
The sewage containing vegetable fibers, animal and vegetable fats, fecal weight, the remains of fruits and vegetables, waste tanning and pulp and paper industry, sugar and breweries, the enterprises of the meat-and-milk, canning and confectionery industry is the reason of organic pollution of reservoirs.
Growth of the cities, rapid development of the industry, agriculture intensification, considerable expansion of the areas of the irrigated lands, improvement of cultural and community conditions and some other factors complicates problems of providing with water more and more.