Theme-8-3-Exchange of flow between a river and aquifer system.

Abstract

A mathematical groundwater flow model has been developed to predict the exchange of flow between a partially penetrating river and a homogeneous infinite aquifer. The model considers the changes in river stage and corresponding changes in river width. Given the values of aquifer parameters, the transmissivity and the storage coefficient, the saturated thickness below the river bed, saturated thickness far away from the river, the initial width of river at the water surface and depth of water in the river, the model can predict the exchange flow rate between the aquifer and the river consequent to passage of a single or several successive floods. From the study it is found that in case of a partially penetrating river the exchange flow rates are reduced significantly in comparison to those of a fully penetrating river due to river resistance. In case of a partially penetrating river the peak inflow tends to occur simultaneously with the occurrence of peak stage. It is found that about 25% of the aquifer recharge comes back to river after the recession of a typical flood. A five times increase in river width during the passage of a flood may cause the maximum inflow rate from river to increase by two times in comparison to the maximum inflow rate from a river whose width does not change abruptly.