Assessment of Interactions between River and Aquifer in the Gowri-hole Sub-catchment

Surface water interacts with groundwater in many types of physiographic and hydrogeological conditions. Exchange of water varies spatially and temporally due to the effect of natural and anthropogenic factors. Interactions between a river and the underlying aquifer systems are often difficult to observe and measure. The objective of the present study is to analyze the spatial and temporal variation of river-aquifer interactions in the Gowri hole sub-catchment and quantify the amount of flow exchange between river and aquifer. In the study, a new conceptual model is developed using RIVER package of Three-Dimensional Finite-Difference Modular Groundwater Flow Model (MODFLOW) for the simulation of river-aquifer interaction processes. The subcatchment of Gowri hole, which is a tributary of Kumaradhara river spread across an area of 134 km(2) is considered. The model was calibrated from June 2004 to May 2010 under the transient condition with a daily step input of all necessary hydro-geological data. The calibrated model was validated from June 2010 to October 2012 from two monthly observation wells of Department of Mines and Geology and one seasonal observation well of Central Ground Water Board (CGWB). Gowri hole acted as a gaining river during the monsoons due to aquifer discharge and acted as a losing river due to river leakage during post-monsoon and summer months. River leakage continued to occur upto the end of summer months resulting in fragmentation of few river segments. Aquifer discharge sustained to exist even in the summer period avoiding the low flow river segments from drying.