In arid areas, stream–aquifer water exchange essentially sustains the growth and subsistence of riparian ecosystem. To quantify this effect for intensity and range, a stream–riverbank scheme was incorporated into a state-of-the-art land model, and some runs were set up over Heihe River basin, northwestern China. The results show that the hydrology circle is significantly changed, and the ecological system is benefitted greatly by the river water lateral transfer within a 1 km range to the stream.