TR-11 : Study of parameters affecting base flow

Abstract

Base flow computation plays an important role for assessment of lean flow in a river. airing passage of flood in a river the river stage rises which leads to recharging of the aquifer. Besides the aquifer also gets recharged by rainfall. The changes in river stages are abrupt whereas the changes in the water level in an aquifer at some distance away from the river are slow. In the present report the base flow has been computed for generally observed river stage and groundwater table hydrographs. It is assumed that the changes in river stage occurs during the monsoon period during which the water table rises exponentially. Beyond monsoon the water table decays in a exponential manner and the river stage remains constant more or less. In the present analysis the base flow has been computed for such variations.

One dimensional Boussinesq's equation has been solved and Cuhamal's approach has been applied to find the aquifer response for varying river stages. The methodology provided can be used to predict the base flow for any pattern of changes in the river stage and the water table. It is found from the study that the base flow will be sustained for longer periods by aquifers having higher T and (t values. Also it is found that the base flow does not follow an exponential decay curve.