Numerical Simulation of Groundwater Flow Regime in a Weathered Hard Rock Aquifer: A Case Study

Numerical simulation of groundwater flow regime in weathered hard rock region is a valuable tool to assess the groundwater resources and to understand its hydrodynamics of a basin. One such study was canied out in Bukdaleru River basin, a hard rock region in Nalgonda district, Andhra Pradesh, India. Recurring droughts and increased exploitation of groundwater to meet the growing needs of drinking water and irrigation had resulted in the decline of regional groundwater levels, causing deterioration of groundwater quality in the basin. In order to evolve future pumping schemes, a preliminary mathematical model of phreatic aquifer was conceptualised, constructed and calibrated in two stages viz., steady and transient conditions. The calibrated model was then used to predict the aquifer behaviour for the next five years. The model study indicates that the phreatic aquifer can sustain the present withdrawal of 28 x 10⁶ m³/year without furlher decline of water level. Any additional increase of withdrawal in the shallow aquifer will result in progressive decline of water level, as the average annual dynamic reserve is only about 28 x 10⁶ m³. If the present model is refined and validated through additional field data, then optimal utilisation schemes can be evolved.