Water Conservation

The hydrosphere refers to that portion of the earth that is made of water, including all oceans, lakes, rivers, streams, glaciers, and underground water. Less than 3% of the water of Earth is freshwater, an amount that includes polar ice caps, glaciers, groundwater, surface water of rivers and freshwater lakes, and even atmospheric water. However, the amount of freshwater useable by people and other members of the biosphere is less than 0.5% of the total (this is water in rivers and lakes, and in the ground). This relatively small amount of available freshwater is recycled and purified by the action of processes within the hydrologic cycle, including evaporation, condensation, precipitation, and percolation through the ground. All life depends on the availability of freshwater.

Of all the freshwater used directly by humans, agricultural irrigation accounts for about 70% of the total. The remainder is used for industrial and domestic purposes. However, these proportions vary widely due to the climatic and economic conditions of the particular locality. Within this century, one third of the countries situated in areas of water scarcity may encounter severe water shortages. By 2025, two thirds of the world's population is likely to live in areas of moderate or severe water shortage. The need for more effective conservation of the limited supplies of water that are available for use by people and required by natural ecosystems will intensify as water stress grows.