Impact of groundwater pumping on river flow

In many regions of the world more groundwater is used than recharged by precipitation or infiltrating river water. While overuse of groundwater can have a variety of undesirable effects, among the most immediate and visible effects are reduction of river flows and the impact on freshwater ecosystems can be devastating.

In an alluvial aquifer, groundwater pumping can reduce the flow of water in a river in two ways: 1) pumping can intercept water that would otherwise discharge into the river; 2) pumping draws groundwater levels down below the level of the river and river water will infiltrate. In this study the impacts of groundwater pumping on river flow are estimated using a coupled global-scale groundwater-surface water model. Results show that nearly half of the pumped groundwater reduces river flow. Globally, approximately 20% of the pumped groundwater comes from increased river capture and 16% from a reduction in storage (averaged over the model period 1960-2010). Critical thresholds for groundwater discharge to support ecological integrity have already been crossed due to groundwater pumping in 15-21% of all river basins and are likely to be crossed in more than half of all river basins by 2050.