A STUDY OF STREAM AQUIFER INTERFLOWS

Abstract

The prevalent practice of estimating the insitu stream-aquifer interflow essentially comprises of monitoring the stream stage and the water elevation in a well located close to the stream. The measured difference between the two levels and the distance of the well from the stream alongwith the stream section, aquifer thickness and the hydraulic conductivity are employed to estimate the interflows. The estimation Is mostly based upon either Dupult forchheirner assumptions or upon certain semi empirical equations accounting for the addition head loss due to vertical velocities. It is believed that the solution based upon the D-F assumptions Is an exact solution when the stream is fully penetrating. In the present study it has been found that, the procedure of estimating the stream-aquifer interflow, based upon the water level data from an observation well, is quite unreallable and uncertain. A better procedure would be to monitor the piezometric head in x-z plane by a nest of piezometers. The piezometric head data so monitored can be used to draw flow nest and hence the stream-aquifer interflow can be estimated reliably.