Assessment of variation of baseflow contribution to stream flow in a hard-rock aquifer

Stream flow is combination of two major portion of flows as direct runoff and baseflow. Study of baseflow and direct runoff is much needed to understand the hydrology of a watershed, including surface and sub-surface water interaction, and to assess the ecological functioning of streams. Tropical countries like India facing major challenges in water management; especially for irrigation and drinking water. In such regions identification of baseflow sources, knowledge of baseflow availability and analysis of their varied contribution to the stream is needful. Baseflow plays a critical role in maintaining streamflow, especially during pre and post monsoon periods.

Recursive digital filter technique is adopted for the daily stream flow data measured at river gauge stations on Kabini stream of Cauvery basin, to separate baseflow component from stream flow hydrograph. In terms of hydrogeology, since Cauvery basin occupied with hard-rock terrain, it is important to investigate the intra annual variation of groundwater discharge into the stream. In the present study an attempt has been made by considering daily stream flow data at two river gauge observation points, and annual baseflow and baseflow index is calculated through RDF method. The results obtained from RDF method are validated with the help of hydrogeochemical tracers by applying End Member Mixing Analysis (EMMA) to the hydrogeochemical data for the period of 2018-19 hydrological cycle.