Of the sources of water mentioned above, glaciers are the great store-houses of this resource that need to be carefully preserved by limiting developmental activities in their vicinity, and by reducing, if not eliminating, the process of global warning. The oceans are a vast resource, but de-salination is expensive, and as such its waters are considered as a last resort for human consumption. But towing of ice-bergs from polar regions to areas of scarcity has been suggested as a practical alternative. The most common and easily exploitable resources are those that lie between the glaciers or catchment areas and the oceans. Principally, these are

• Ground water
• Rivers and streams
• Lakes and artificial reservoirs and tanks.

Here it must be noted that the rivers and streams have important natural functions, one of the most crucial ones of which is the re-charging of the ground water resources, through the system of acquifers and aquitards that have evolved in each basin through millenniums and natural flow. In an important article in the Journal of Hydrology (No. 133/92, Amsterdam), Dr. W.Z. Zhang of the Wuhan University of Hydraulic and Electric Engg. has given details of his research and shown the direct relationship that exists between water level in a river and that in its aquitard , as well as the varying rates of the latter's re-charge depending on the various water levels in the river. Here it should be noted that water thus stored below the ground surface remains well preserved and free of evaporation losses. In addition, the streams bring down rich alluvial soil, spreading these during floods, maintain lakes and surface wetlands along with their respective bio- diversity (flora & fauna) and support various types of human activities, viz fishing, navigation, tourism and religious activities. Natural lakes and tanks are connected to ground water reserves, and are good sources of water if their re-charge system of aquifers is kept regularly supplied by the streams of the basin. Artificial reservoirs are created upstream of dams and barrages, which prevent the flow of rivers and streams, but are usually designed to store large quantities of waters, which however, are susceptible to evaporation.

Man made irrigation or water supply systems could be assigned two broad categories viz, those that:-

• (a) are in 'Consonance With Nature', whence withdrawal leaves the natural renewable system intact, somewhat like the milching of a cow after its own offspring has partaken of the resources, and
• (b) those that operate 'Contrary To Nature', which grossly interfere with the natural flows of rivers and stream,s and in the process, also distrupt the important natural functions of these water course, often in a self defeating manner.
• Writing in the reputed work, 'Indian Economy Since Independence', Mr. B. Sivaraman, an erstwhile Vice chairman of the Agriculture Commission, has pointed out that the famous Irrigation Commission of 1972 found that " ... if the benefit from the government surface irrigation scheme is one unit, the benefit from a government ground water scheme is two units and that from a private irrigation scheme- five units". He has also pointed to some of the inadequacies of the major and medium irrigation works (involving dams, barrages and canals} pertaining to siltation, poor maintenance and the inadequate system of water distribution, which being state managed, is often rife with corruption and a lackadaisical attitude of concerned officials. The government ground water schemes are usually located close to the command areas and distribution present fewer problems, though management by officials retains the handicaps of the major surface irrigation schemes. Private tubewells are the most cost-effective, but of late, the diversion of the re-charging river waters in canals is leading to much lowering of the water table, thereby increasing the capital and operational cost of farmers' investment in these schemes. We must also take note of the co-operative water panchayats that have been a great success in Maharashtra in harnessing water resources through minor surface and cooperative tubewell schemes.