Groundwater pumping versus surface-water take

Surface-water bodies and aquifers are normally connected and it is widely recognised they should be treated as one entity. Numerous studies were done to analyse the effect of groundwater pumping on nearby streams, however, little is known on the differences of effects between surface-water take and a pumping well of equal rate. The question, which often arises by water resources managers and allocation authorities, is whether to allocate or consent-transfer from a surface-water body or from an aquifer. This study explores the different effects of each case and makes a comparison using analytical analysis and numerical models. A hypothetical model is presented where two cases are considered: (1) a stream water take through a diversion and (2) a pumping well. In both cases, the drawdown and water budget of surface and groundwater are presented. Results show the pumping well produces high drawdown in the aquifer, and induces stream leakage. The stream leakage results in stream level drop. It takes a long time for such a system to stabilise or to reach a steady state. In contrary, the direct stream water take produces much lower drawdown in the aquifer, albeit higher drop in stream water level. The latter case stabilises and reaches steady state conditions considerably faster than the first one. These results reveal it is recommended to allocate from surface-water bodies than aquifers as the impact is less and for a shorter time, given the same allocated volume of water.