RAIN WATER :
Rain water is the most important sources of water and the purest from of natral water. It is naurally distilled water as the water from sea, rivers etc. , first evaporates in the great heat of sun to form clouds which afterwards condense and water comes down in the form of rain. As the rain water falls on the surface of the earth and flows as streams or seep through through earth’s crust, it takes up dust particles, oxygen, carbon dioxide, nitrogen and other dissolved and suspended solids present in the atmosphere and solid.