Water is one of the most important elements of the environment, it is necessary for human life, animals and plants. The body needs water more than anything else with the exception of oxygen. Without food, a person can live more than a month, and without water only a few days. Dehydration leads to irreversible effects and death.
All water reserves on the Earth are united by the concept of «hydrosphere». The hydrosphere means a complex of aqueous bodies including oceans, seas, rivers, lakes, reservoirs, swamps, groundwater, glaciers, snow cover, and drip-liquid water in the atmosphere. Hydrosphere is of great importance for the life and health of mankind. Water regulates the climate of the planet, provides economic and industrial activity of people, acting as its condition and object, is part of all living organisms that inhabit the Earth including the human body. In any living organism, water plays the role of a structural component, a solvent and a carrier of nutrients, participates in biochemical processes, regulates heat exchange with the environment.
The main problems associated with the hydrosphere of the planet are the conditions for providing the population with water, the quality of water and the possibilities for its improvement. Until recently, these problems have not been so acute due to the relative purity of natural water sources and their sufficient number, but in recent decades the situation has changed dramatically. Huge concentration of the urban population, a sharp increase in industrial, transport, agricultural, energy and other anthropogenic emissions have led to disruption of water quality, the emergence of chemical, radioactive, and biological agents unusual for the environment in water sources have been found. All this makes the effective water supply of the population the leading problem in the life of modern mankind.