TR(BR)-12/96-97 : Analysis of flow to a multiaquifer well : A numerical approach

Abstract

Existence of multi-aquifer system are common in a sedimentary basin. A well drawing water from more than one aquifers that have good quality of water, increases the yield of the well and in most of the cases is economical. In most of the studies done so far, pumping from only one layer has been considered. In very few analytical studies, pumping from more than one aquifer has been dealt. The available analytical solutions can not take into account the complex boundary conditions and spatial variations in the values of the parameters within the flow domain. For these, numerical models are required. However, three dimensional groundwater flow models can not accommodate a well taping more than one aquifer of a multi-aquifer system.

In the present study, unsteady flow towards a fully penetrating well screened in both the aquifers of a two-aquifer system separated by an aquitard has been analyzed using numerical approach. The aquifers are considered to has different hydraulic characteristics. A three dimensional groundwater flow model developed by USGS has been used to generate the unit pulse coefficients. Utilizing these, unit pulse coefficients, methodology has been developed for obtaining the contribution of each aquifer and drawdown in the aquifer. The results using the methodology have been compared to those available from alialytical study. Therefore, using the present methodology, a three dimensional groundwater flow model or MODFLOW can be successfully used for modelling flow to a multi-aquifer well incorporating the spatial variations in the parameters within the flow domain.