4-River Aquifer Interaction - A Problem With Varying Stage and Water Spread Area.

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 while predicting the exchange of flow between the river and the aquifer. Knowing the aquifer parameters, the transmissivity and the storage coefficient, the saturated thickness below , the river bed, the initial width of river at the water surface, depth of water in the river, and an equation describing river cross section, the model developed 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 recharge 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 abrupt increase in river width during passage of a flood results in doubling the maximum recharge rate.