THE DRAWDOWN DISTRIBUTION IN AND AROUND A WELL PUMPING FROM A TWO-REGION AQUIFER

The non-steady flow towards a well pumping at a constant rate from the center of a circular region that has different hydraulic properties than the surrounding aquifer is analyzed. Equations are derived for the temporal variation and spatial distribution of the drawdown within both the inner and outer region of the aquifer. These equations provide a means for analyzing data from wells completed in such aquifers to determine the hydraulic properties within both regions of the aquifer. Examples of the time-drawdown, distance-drawdown, and composite-drawdown response of observation wells completed within the inner or outer region of the aquifer are presented for conditions representing either a higher or a lower transmissivity for the inner region. As illustrated by these examples, the temporal variation of drawdown in wells within both regions is eventually controlled by the hydraulic properties of the outer region, and the spatial distribution within each region is controlled by the properties of that region.