Competition between topography- and compaction driven flow in a confined aquifer: Some analytical results

An analysis is presented of the competition between topography- and compact ion-driven flow in a confined aquifer. The aquifer crops out and is unconfi ned in an area with an elevated water table. In the absence of compaction, the elevated water table drives the flow toward areas with a lower water ta ble, and leakage occurs from the aquifer through an overlying aquitard. Und er these conditions, recharge occurs in the outcrop area. When sedimentatio n occurs above the aquifer away from the outcrop area, compaction tends to reverse the flow direction in the aquifer, causing expulsion of groundwater in the outcrop area. The actual flow field arises from the competition bet ween the two driving mechanisms. An analytical expression for the combined flow field is derived in which the contribution from both mechanisms is app arent. The expression is useful as a practical guideline for estimating whe ther or not compaction can be safely ignored in regional groundwater-flow s tudies of confined aquifers.