Spatiotemporal Variation in Water Use Efficiency and Its Determinants in 2000--2014 in the Source Region of Yellow River.

[Objective]Water use efficiency (WUE) and the factors affecting its spatiotemporal variation are important in water management at catchment scale. The objective of this paper is to analyze the variations of WUE and its determinants in the source region of Yellow River (SRYR).[Method]The analysis was based on MODIS remote sensing data, from which we estimated the ecosystem WUE from 2000 to 2014 and its spatiotemporal variation, as well as the underlying drivers using trend analysis and correlation analysis.[Result]Spatially, the mean annual WUE increased from the west to the east, with an average of (0.59±0.35) gC/(m² •mm) from 2000 to 2014. Temporally, WUE did not show any decreasing or increasing trend (p>0.05). The areas that have seen a significant increase in WUE account for 30.29% of the studied region, distributing mainly in the west and north of SRYR. Areas with low and medium vegetation coverage are dominated by grassland and farmland. Spatial variation of WUE was mainly affected by hydrothermal factors and leaf area index. [Conclusion]In the context of mediating the detrimental effects of climate warming and flooding, improving vegetation in areas with low and medium vegetation coverage is expected to enhance WUE significantly. [ABSTRACT FROM AUTHOR]