2-Characterization of Groundwater Recharge in a Crystalline Watershed Through Recharge Process and Groundwater Flow Models.

Abstract

Parkal watershed with an extent of about 12.35sq.km. is a hard rock granitic aquifer system and is situated in Warangal district, Andhra Pradesh. The recharge to the aquifer mainly occurs due to rainfall during monsoon season and has been estimated using a recharge process model. The recharge has been estimated as a balance component after accounting for interception losses, surface runoff, evapotranspiration based on agroclimatological conditions and soil moisture status. Surface runoff has been estimated from SCS (Soil Conservation Service) curve number model. Aquifer parameters viz., transmissivity and specific yield have been estimated through pump tests at four locations. The aquifer system has been modeled as a single weathered leaky aquifer using integrated finite difference method on a nested squares grid. Steady state condition of the aquifer system has been simulated assuming an equilibrium condition during June, 1981. The average annual recharge estimated over 10 years period has been fed as input to the aquifer. During the steady state calibration, the transmissivity values assigned at various meshes have been modified in some pockets to match the computed and observed water level contours. At some places minor changes have been resorted in the draft distribution arrived from well inventory and pumping hours. Irrigation return seepage has been found to be contributing significantly to the groundwater regime in the ayacut area of Damera cheruvu. The monthly recharge estimates of the recharge model have been fed as input to the aquifer model in the transient condition. The aquifer model has been refined after several trials and the monthly recharge estimates were found to be adequate for simulation of the water table behaviour.