Water is an Amazing Liquid.
The presence of a useful and safe drinking and industrial water is by no means self-evident fact.
In our solar system, life is only possible within a very thin spherical shell that surrounds the heart as a star at a distance of about 150 million km. And only this layer, whose thickness in relation to the diameter of the solar system is no more than 4%, is so favorable that the water is present in all three forms: solid, liquid and gaseous. In the center of different features such a small region of space is our land, water resources, which account for 1.3 billion km3. However, only 2.8% of this amount accounted for by fresh water, and much of it centered on the Earth in the form of ice at both poles and the highlands. Slightly more than 0.5% of the total number of terrestrial water resources are fresh water in liquid or vapor state. It was only a hundredth of this number fills rivers and lakes or in the atmosphere as water vapor, the remaining part of the same - it's ground and other underground water, half of which lies at a depth of 800 m.
In turn, moisture in the air compared to water of rivers and lakes - only a negligible portion and is one-thousandth of the total water on our planet. However, this one thousandth still is 15 km3. Above our heads, in the atmospheric layer precipitation there is almost 20 times more water than it is contained in the Aral Sea. In a single storm cloud lies 100 thousand tons of water.
The huge water reserves are concentrated in the air, updated on average every 10 days. In the form of rain they fall to the ground and replenished again through evaporation. This process requires enormous in size energy. To return to vaporize all the precipitation that falls during the year worldwide and 0.5 million km 3, would need energy generated $ 450 million large power plants. One sixth of the total amount of precipitation falls on land. Slightly more than half this amount is carried away by the flow of rivers into the sea. The balance of 40 km3 of fresh water falls on the continents. It is not enough. But we must spend wisely and sparingly water, as the above energy balance, as well as the possibility of providing fresh water by precipitation clearly indicates that we will never be able to own a tangible increase the amount of fresh water. What is the point to completely contaminate wastewater, these huge masses of fresh water and then with unprecedented technical repair costs less than 1% of the volume of contaminated water? No less foolish pride for its outstanding achievements by industrial, Which lead to the production by means of costly desalination plants than half of one thousandth of the total number of abundant continental precipitation for 1975