Spatio-temporal change and influencing factors of evapotranspiration in the Huaihe River Basin based on MODIS evapotranspiration data

The Huaihe River Basin is an important grain production area in China, and the utilization of water resources in the basin is of great research value. To explore the spatial-temporal characteristics of evapotranspiration (ET) in the Huaihe River Basin from 2000 to 2014 and its response to climate change and land use, MOD16/ET products, precipitation and temperature data, and land use data are used in this article. The results show that ET is high in the south and low in the north of the study area. The annual average ET is 589.1 mm, the seasonal change of ET decreases in this order: summer (257.4 mm) > spring (144.6 mm) > autumn (121.8 mm) > winter (66.3 mm). ET has an increasing trend at first and then a decreasing trend over the 15 years. According to the results of trend analysis, 31.4 % of the regions showed a significant or extremely significant decreasing trend of ET, 5.4% of the regions showed a significant or extremely significant increasing trend of ET, and 63.2% of the regions showed no significant change. Analyses of the driving climatic factors on ET change shows that about 52.0% of the study area was impacted by non-climatic driving factor, while 44.1% was driven by precipitation, and 2.4% and 1.5% were separately driven by the two climate factors and temperature, indicating that the ET change in this region is mainly affected by human activities. The average value of ET of the four types of vegetation coverage land use decreased in this order: woodland (639.29 mm) > paddy field (633.24 mm) > dry land (568.72 mm) > grassland (556.37 mm). According to the statistical results of ET of different land use types from 2000 to 2014, the conversion of grassland to paddy fields significantly increases ET, and the conversion of dry land to grassland and woodland to dry land significantly reduces ET.