Water is life. Survival of plant and animal kingdom depends on availability of utilizable water. Water resource potential of India has been assessed as 186.9 m ha-m (million hectare meter). Majority of this comes from rainfall. Out of countrys annual average rainfall of 400 m ha-m, utilizable water is only about 112.3 m ha-m comprising 69.0 m ha-m surface water and 43.3 m ha-m ground water. It is estimated that Indias water requirement will be about 84.3 m ha-m by 2025 and 118.4 m ha-m by 2050 due increase in population and significant expansion of water use in agriculture and industries. As annual availability is far more than the demand, researchers often (Kumar et al 2005) argue that there should not be any scarcity of water in near future. However, India is facing droughts in some parts or regions or others almost every year.
In India, more than 70 percent of annual rainfall takes place during three months South West monsoon. However, majority of this precipitation runs off to sea resulting water scarcity in dry seasons especially in regions where irrigation coverage is less (FAO, 2010).
Many resorts to ground water deployment to meet demands. However, non judicious exploitation of ground water for irrigation purposes in some parts of India is already showing signs of another crisis. Studies report that more than 26 cubic miles of groundwater has already disappeared from underground aquifers in large areas of Haryana, Punjab, Rajasthan and the nation's capital territory of Delhi, between 2002 and 2008 (NASA 2009).
Global Runoff Data Centre, University of Hampshire and International Earth Science Information Networks have projected that around 30% area of India falls in the extreme water scarce zone having less than 500 m3/person/year supply of renewable fresh water.
Though India is blessed with many major rivers and their tributaries but occurrences of flood and drought are regular causing tremendous adverse impact on food production besides yielding substantial loss of fertile top soil and countrys wealth. Therefore, both development and management of water resources with scientific data base is a pre-requisite for achieving sustainable development.
Water resource development has many faces. At macro level, it is primarily dealt through construction of large dams and reservoirs for irrigation and power generation. At micro level, watershed development programme plays a major role for conservation of soil and water resources. However, for both macro and micro level activities need basic hydrologic and topographic information such as drainage network, water availability,gradient etc. for deriving manageable units of interventions.