Hydrogeological investigation and groundwater modeling in a weathered granitic rock region of southern India

In most parts of India especially in the southern part, groundwater forms the only source of water, due to limited availability of surface water resources and non perennial rivers. A study is being carried out on the hydrogeological charecterisation and groundwater modeling of hard region of southern Indian located 130 km south east of Hyderabad, India. The objectives of this study are to charecterise the hydrogeology and simulate the groundwater flow conditions by numerical modelling. Geologically this area mainly comprises of granite and granitic gneisses of late Archaen. Cuddapah formation overlies this basement rock. The annual groundwater level fluctuation in this area is around 8 m. The principle source of groundwater recharge is rainfall. The rainfall recharge is about 10% of rainfall. In general the groundwater flow is towards southeast direction. Ca-HCO3, Na-Cl, Ca-Na-HCO3 and Ca-Mg-Cl are the dominant groundwater types in this area. The uranium concentration in the groundwater of the area ranges from BDL to 205.3 ppb due to reasonably high uranium in granitic rocks here. About 22.15% of the groundwater samples have uranium concentration above the permissible limit of 30 ppb as set by USEPA. Groundwater flow modeling was carried out using finite element code FEFLOW. Simulation of hydraulic heads along with movement of radionuclides was successfully carried out with the developed model. The maximum dose that may be received by the members of the public through the groundwater drinking pathway is about 2.5 times lower than the drinking water guideline of 0.1 mSv/y. Sensitivity analysis of the model show that Kd is one of the most sensitive parameters in the radionuclide transport.