Regional Evapotranspiration Change In The Piedmont Plain Of Golmud River Basin

With little precipitation and strong evaporation,the Golmud River Basin is located in the Qaidam Basin,Northwest China.With the urban and industrial development,regional water consumption has increased and the increased water use will cause more serious aridity and water shortages in future.Compared with precipitation and runoff processes,which are intermittent and nonlinear,daily continuous ET can better reflect regional hydrological changes.Few studies have focused on the Golmud River Basin because the conflict between water use and water demand has become a serious issue in recent years.Due to lack of spatial and temporal variations in long-term ET,long-term regional water use in the Golmud River Basin cannot currently be accurately reflected.Research on ET change can help us understanding the water use in recent years and the water demand in the future.Further,the analysis of ET trends and underlying mechanisms is expected to improve the scientific management and sustainable development of water resources in the Golmud River Basin.Taking the piedmont plain of Golmud River Basin as the research area,this paper analyzes the temporal and spatial distribution characteristics of evapotranspiration(ET)from 2001 to 2018using medium resolution remote sensing data.Furthermore,a ET data set with high temporal and spatial resolution is formed by ESTARFM spatiotemporal fusion algorithm.The trend and significant change of ET in the continuous time series of the study area were analyzed quantitatively,and also the controlling factors of regional evapotranspiration were revealed.The main results are as follows:(1)In general,the ET exhibited an increasing trend from 2001 to 2018 in the Golmud River Basin.Specifically,the trend can be divided into three periods:a slight increase period during2001-2004,a small change period during 2005-2008,and a fast fluctuating increase period during2009-2018.Spatially,ET was mainly observed in south-central vegetation development areas and northern saline pond areas.(2)The ET of most regions in the study area exhibited almost no change,accounting for71.65%of the total area.The areas with significantly increasing ET reached 1235.75 km~2,which constitute 27.07%of the total area.In contrast,both slight or significant decreasing ET trends occurred in only 0.81%of the study area.(3)Most ET increase areas were spatially concentrated in summer,followed by autumn and spring.On the opposite,the smallest change of ET is mainly occurred in the winter season.The ET of each geomorphic unit in the study area showed an overall growth trend from 2001 to 2018,and the growth rate of saline pond areas was the fastest.The ET of different geomorphic units was the largest in Salt Lake area,followed by fine soil plain,salt marsh,and the piedmont Gobi gravel plain.(4)Air temperature,precipitation,NDVI and soil moisture had significant positive effects on ET.In addition,human-induced changes in land use had a dominant effect on ET trends in the study area.The farmland area,salt ponds area and groundwater exploitation,which are mostly affected by human activities,have been increasing continuously from 2001 to 2018.These changes have led to the change of regional ET to a great extent.