Water is the most vital substance in the natural world. Water occurs in three different state; these are solid, liquid and gas. All these forms occur naturally in various environments. Water in the natural state normally, contains various organic and inorganic minerals, but in its purest form it is a tasteless, odorless, colorless liquid that is made up of two hydrogen atoms and one oxygen atom as shown in the figure below:
             The freezing point of water is 0° C, and its boiling point is 100° C. Water reaches its maximum density at 4° C and expands upon freezing. Water is one of the best known ionizing agents. Water combines with certain salts to form hydrates and reacts with metal oxides to form acids.
             Water is the only substance that occurs at ordinary temperatures in all three states of matter. As a solid, ice, it forms glaciers, frozen lakes and rivers, snow, hail, and frost. It occurs in the liquid state as rain and dew, and it covers three-quarters of the Earth's surface, swamps, lakes, rivers, and oceans. Water also occurs in the soil and beneath the Earth's surface as a vast groundwater reservoir. As gas, or water vapor, it occurs as fog, steam, and clouds.
             A renewable resource is one that is replaced naturally faster than it is removed utilized. All forms of naturally occurring water are renewable; this is because of the effect of the hydrological cycle. Water vapor, evaporated from water and land surfaces and from living cells, circulate, through the atmosphere and falls as rain, hail or snow. When it reaches the E h, water either flows into streams and then into oceans or lakes, or it enters, or infiltrates the soil. Some water becomes soil moisture, which may evaporate directly or move up through the roots of plants and be released by leaves through transpiration. Some water percolates downwards, accumulating in the so-called zone of saturation to form the groundwater reservoir, the upper surface of which is known as ...