Hydrosphere ecology

Water, its circulation and its role in the biosphere. Water is the most common compound on the planet, the basis of all life processes, the main source of oxygen which process on Earth is photosynthesis. (As it is known, the flora consists of 90% water, animals and people is at 75%, while its loss at 10-12% for the latter means death.) Water can be in three aggregation States: liquid, solid and gaseous, and liquid-only fresh and salty, and the solid and gaseous — just fresh.
Permanent water cycle occurs on the following conventional pattern: precipitation, surface and underground run-off, infiltration and evaporation is the transfer of water vapor in the atmosphere and its condensation is the second rainfall. In close connection with the concept of "water cycle" there is the notion of "water". Under the last means the gradual change of water, its resurgence during the cycle. Water exchange occurs very slowly in the glaciers (8000 years) and groundwater (about 5000 years old), but thousands of times faster in pairs of the atmosphere, soil moisture and River (channel) waters.
The main condition of life on Earth is not just water, but clean, fresh drinking water, without which man cannot carry more than 3-4 days. Fresh water needed to extract nutrients from food, excretion of wastes and toxic substances from the body. With the help of water body gets rid of harmful bacteria and their toxins. However, the concept of "fresh water" is very relative. (Usually is not more than 1 g of salt per 1 liter, but salt may vary.) Many countries have their own requirements (Gosts) to water: it security epidemic, chemical composition, taste, smell, colour, transparency. By the way, the water standards, adopted in Russia, not the West. In reality, however, the quality of water in our taps leaves much to be desired.