Spatial and Temporal Characteristics of Reference Evapotranspiration Trends in the Haihe River Basin, China

Abstract

In this study, the spatial and temporal patterns of trends for reference evapotranspiration (RET) at 34 meteorological stations (between 1957 and 2007) in the Haihe River basin, China, were analyzed using the Mann-Kendall (MK) test and the Sen’s method. To reveal the possible causes and main driving forces of the changing patterns of RET, the spatial distribution and temporal patterns of trends for four meteorological variables (i.e., temperature, wind speed, relative humidity, and sunshine duration) were examined for each station. In addition, partial relative analysis between RET and meteorological variables and a sensitivity analysis of RET to meteorological variables were conducted. The results show the following: First, the Haihe River basin is dominated by a significant decreasing MK trend in annual RET at >95% confidence level, which is observed at most stations in the eastern and southern areas of the basin. There are no observed trends or significant increasing MK trends in annual RET in the west...