Groundwater evapotranspiration captured by seasonally pumped wells in river valleys

The loss of groundwater through Evapotranspiration (ET) has been reported extensively in the hydrological literature. This ET loss, however, can be lessened by a pumping well that lowers the water table within the cone of depression. This paper quantifies the amount of groundwater ET captured by irrigation wells in river valleys where pumping induces stream water infiltration. Our analyses were based on hypothetical stream–aquifer systems and a case study in the central Platte Valley, Nebraska, where groundwater irrigation supports agricultural development. Interactions of groundwater-stream–evapotranspiration were simulated using MODFLOW. The results suggest that the amount of ET capture varies from about 2–9.4% of the groundwater pumpage, and that a number of hydrogeologic parameters can affect the ET captured. They can include depth to the water table, distance between stream and well, and aquifer hydraulic conductivity. Results from the case study indicate that about 11% of groundwater pumpage in a 3200-m wide zone across the Platte River came from the ET capture. Neglecting the ET capture will likely overestimate the rate of stream depletion. On the other hand, reducing groundwater pumpage can increase the river flow and aquifer storage, as well as increasing groundwater ET to about 10% of the reduced pumpage. A groundwater conservation program thus needs to consider the extra amount of ET loss.