ESTIMATION OF GROUNDWATER RECHARGE IN A BASALTIC AQUIFER

The Adila basin, located in the basaltic terrain of the Deccan Traps a round Solapur in Maharashtra state, India, covers about 585 km2 (latit ude 17-degrees-35' to 17-degrees-57'N and longitude 75-degrees-47' to 76-degrees-05'E). The soils in the basin are Vertisols and the soil th ickness ranges from 0.7 m along the boundaries to 1.5 m in the centre of the basin. Daily rainfall and open pan evaporation data have been c ollected from the hydrometeorological station at Solapur. These two hy drometeorological parameters, along with the local agroclimatological conditions and soil characteristics of the area have been used to esti mate surface runoff and groundwater recharge in the water balance mode l. Interception loss from the canopy cover has been assumed as 0.2 mm per rainfall event. The surface runoff has been calculated using the S oil Conservation Service runoff curve number model. A representative c urve number has been selected based on vegetation, land use and agricu ltural practices. Evapotranspiration coefficients of the general crops grown in the area, i.e. maize, millet, sorghum etc., have been used d epending on the time from the sowing date to the end of the harvest. T he average annual groundwater recharge is 51 and 23 mm for the two Ver tisol conditions of the uplands and valleys of the basin, respectively .