干旱区生态环境知识资源中心

The spatial variation of evapotranspiration (ET) and its relationship with vegetation and groundwater depth in the arid Yinchuan plain of China was studied by combining remote-sensing data with groundwater depth observation. The vegetation cover was quantified with the normalized difference vegetation index (NDVI), ET was estimated with the surface energy balance system, and the groundwater depths were measured in monitoring wells. The results show that an area of the plain is covered by vegetation when the NDVI of the area is larger than 0.2 and that groundwater depth is an important factor influencing the ET in the arid region: the deeper the groundwater, the less the ET. The threshold depth of groundwater evaporation is 4 m in the rainy season. A method of quantifying soil evaporation at a regional scale was also presented in this study. The results obtained in this study are useful for future study of the regional water cycle and climate.