Spatiotemporal patterns of water table fluctuations and evapotranspiration induced by riparian vegetation in a semiarid area

Abstract Groundwater evapotranspiration ( ET g ) links various ecohydrological processes and is an important component in regional water budgets. In this study, an extensive monitoring network was established in a semiarid riparian area to investigate various controls on the spatiotemporal pattern of water table fluctuations (WTFs) and ET g induced by riparian vegetation. Along a vegetation gradient (∼1200 m), diurnal WTFs were observed during a growing season in areas covered by woody species ( Populus sect . Aigeiros and Juniperus virginiana ) and wet slough vegetation ( Panicum virgatum and Bromus inermis ) with deeper root systems; whereas, no diurnal WTFs were found in the middle section with shallower‐rooted grasses ( Poa pratensis and Carex sp .). The occurrence of diurnal WTFs was related to temperature‐controlled plant phenology at seasonal scales and to radiation at subdaily scales. Daily ET g in the mid‐growing season was calculated using the White method. The results revealed that depth to water table (DTWT) was the dominant control on ET g , followed by potential evapotranspiration ( ET p ). By combining the effects of DTWT and ET p , it was found that at shallower depths, ET g was more responsive to changes in ET p , due to the closer linkage of land surface processes with shallower groundwater. Finally, exponential relationships between ET g / ET p and DTWT were obtained at the study site, although those relationships varied considerably across the sites. This study demonstrates the complex interactions of WTFs and ET g with surrounding environmental variables and provides further insight into modeling ET g over different time scales and riparian vegetation.