In this 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. Existence of multi-aquifer systems is common in a sedimentary basin.
Wells drawing water from more than one aquifer which 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 and not from more than one aquifer has been considered.
The available analytical solutions cannot 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 flow models cannot accommodate a well tapping more than one aquifer of a multi-aquifer system. The aquifers are considered to have different hydraulic characteristics.
In this study, a three dimensional groundwater flow model developed by USGS has been used to generate the unit pulse coefficients. Utilizing these unit pulse coefficients, a 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 analytical studies. Therefore, using the present methodology, a three dimensional groundwater flow model or MODFLOW can be successfully used for modeling flow to a multi-aquifer well incorporating the spatial variations in the parameters within the flow domain.
Download the report here: