Stream-aquifer interaction assessment using riparian evapotranspiration estimates from remote sensing algorithms

Stream-aquifer interaction in the absence of proximate, localized pumping along the stream length is a major determinant of water balance in long river reaches. There is also considerable debate on whether improving on-farm irrigation efficiency in the river valley would lead to stream-wide water use efficiency. Techniques for assessing unmeasured returns to the stream would include modelling the groundwater processes in the riverine aquifer, requiring information on hydrogeological parameters for the associated aquifers and the stream-wetted perimeter, and irrigation applications on reliable spatial and temporal scales. Assessing these parameters and operational variables is an arduous task requiring extensive drilling and testing. This study explores the technique of using water balance studies for determining unmeasured returns to the stream, using ET estimates for riparian areas from remote sensing algorithms. The study of the Colorado River reach between Parker and Imperial dams indicates the need for revising the current practice of using constant fractions of diversions in the different months to assess the unmeasured returns.