Measurement of Natural Recharge in India

The broad pattern, emerging from recharge measurements in various basins ranging in area from few tens to few thousands of square km indicates an annual input of about 16% (or 100 mm) of the precipitation in the Indo-Gangetic alluvial tract and about 8% (or 60 mm) ofthe precipitation in the Peninsular hard-rock areas. The Tritium recharge measurements are compared with those obtained by using hydro-meteorological and hydrogeological methods. The relation between recharge values and water level fluctuations in open wells is studied and regression plots showing dependence of recharge rate on rainfall over granitic, basaltic, sedimentary and alluvial provinces are presented. Data on temporal variation in recharge due to variation in rainfall over three hydrological cycles in a granitic watershed in the semi-arid area is presented. The utility of such studies in prediction of recharge from rainfall data is illustrated.