Water scarcity is due to the following causes :— (i) Water availability varies over space and time mainly due to the variation in seasonal and annual precipitation. (ii) Rapid urbanisation is another factor for water scarcity. (iii) Rapid increase in population that demand more and more water. (iv) Industrialisation is another cause, large industrial houses are using more and more water,they also require more water to generate electricity. (v) Rising income levels also create more demand for water. (vi) 96.5 per cent of the total volume of world’s water is estimated to exist as oceans and only 2.5 per cent as fresh water. Nearly 70 per cent of this freshwater occurs as ice sheets and glaciers, while a litlle less than 30 per cent is stored as groundwater in the world’s aquifers.