This chapter deals with ways and means of conservation and optimal utilisation of terrestrial freshwater and preventing its pollution. Non-availability of drinking water has caused immense hardship to whole communities in Africa and to a lesser extent, in Asia. Falkenmark believe that water scarcity may turn out to be the most serious constraint in the Third World Development, if not vigorously addressed. Water is different from other natural resources in being mobile. Most of the water on earth is involved in a continuous movement called the Hydrological Cycle, which is energised by solar energy and gravitation. Biomass growth and human activities are dependent upon the quality and quantity of surface and groundwater which are subject to change. Water quality criteria specify a concentration of constituents in water which, if not exceeded, are expected to result in an aquatic ecosystem suitable for higher use of water. Groundwater figures prominently in water resources planning in any country.