TR(BR)-11/97-98 : Stream aquifer interaction in multi layered system

Abstract

A system of extensive aquifers sandwiched between silty or clayey beds are common in alluvial basins. Such a system is known as multi-aquifer or multi-layered system. Often a river penetrates fully or partially the upper aquifer in such multilayered system. When the river stage rises during the passage of a flood, the upper aquifer is recharged through the bed and banks of the river. The lower aquifers are recharged through the intervening aquitards.

In the present report, a mathematical model has been developed for study of stream-aquifer interaction in (multi-layered system) three aquifer-system in which aquifers are separated by aquitards, considering varying stream-stage and vertical flow through aquitards. The model enables the computation of rate of recharges to the upper aquifer and exchanges of flow among aquifers along with the spatial and temporal distributions of piezomeric heads in the aquifers. The methodology presented by Mishra(1987b) for two-aquifer system, has been shown to be the special case of present formulation.

The model has been validated against the numerical simulation using MODFLOW for different cases. MODFLOW source code was modified to get the exchange of flow from each strip and its spatial and temporal summation. Close reproduction of results using MODFLOW show that the methodology based on discrete kernel approach, is valid for the analysis of the interaction of stream and multi-aquifer system.