Evapotranspiration over the Grassland Field in the Liudaogou Basin of the Loess Plateau, China

Severe desertification on the Loess Plateau of China since the 17th century as a result of improper land use has caused critical soil erosion and water shortages in the lower reaches of the Yellow River. To prevent further soil erosion, it is very important to cover the bare land surface with natural vegetation. Evapotranspiration (ET) over the grassland (Stipa bungeana) in Shenmu County of the Loess Plateau during the growing season is estimated to be about 1 mm day–1, and the ratio of ET to reference Evapotranspiration (ET/ET0) is below 0.3. Evaporation from the bare soil surface simulated by a three-layer soil model is less than ET; that is, ET is 1.5 times greater than evaporation from the soil surface during the growing season.This study examines the relationships among the surface resistance rs in the Penman–Monteith equation, solar radiation, vapor-pressure deficit, temperature, wind speed, and soil water content. Surface resistance (rs) is strongly affected by the vapor-pressure deficit and soil water content.