Water covering approximately three-fourth of the surface of the earth. In spite of this apparent abundance, several factors serve to limit the amount of water available for human consumption/use.

As shown in the table-2, over 97 per cent of the total water supply is contained in the oceans and other saline bodies of water and is not readily usable for most purposes. Of the remaining 3%, a little over 2% is tied up in ice cap and glaciers and along with atmospheric and soil moisture, is inaccessible.

Thus, for their general livelihood and the support of their varied technical and agricultural activities, human must depend upon the remaining 0.62% found in fresh water lakes, rivers and groundwater supplies. Water is mostly used for industrial and municipal purposes. In order to ensure the quality, it is important to monitor water supply throughout taking all the aspects.

Rain water is the purest forms of naturally occurring water. However, water is distributed in nature in different forms such as river water, spring water, rain water and mineral water.