An empirical approach simulating evapotranspiration from groundwater under different soil water conditions

Based on the approaches of FAO24 and FMP1, a new empirical approach simulating evapotranspiration from groundwater (ETgw) under different soil water conditions was proposed in present study. Then, through the data from volumetric lysimeter, the new approach was compared with the two approaches of FMP1, C1 and C2. The new approach gave acceptable simulation results for the treatments under different water conditions, and especially gave better results for the treatments influenced markedly by precipitation or irrigation than the other approaches. The large errors in the late stage in 2009 might be due to the effect of the early maturity of winter wheat. It also indicated that the critical soil water storages in the equation in FAO24 were not suitable to describe the relationship between ETgw and soil water storage in root zone when water table was at or above 150 cm depth, and could be replaced with the storage corresponding to the field capacity and the steady storage. The new approach was more suitable for estimating the ETgw under different soil water conditions comparing with C1 and C2.