Abstract
Evapotranspiration (ET), including evaporation from soil and water surfaces and transpiration from vegetation, influences water distribution in the soil-plant-atmosphere continuum, especially in arid areas where water is a key limiting factor. Therefore, understanding the spatiotemporal dynamics of ET, including its two components of soil evaporation (Es) and vegetation transpiration (Ec), can be useful for water resource management and ecological restoration in arid regions. Based on ET data from 2002 to 2012, the spatiotemporal variations in ET were evaluated in the Shiyang River Basin in arid Northwest China. The results showed the following: (1) spatially, ET decreased from upstream of the Qilian Mountains to the middle and downstream, with a mean annual value of 316 mm; (2) temporally, ET showed a single peak curve throughout the year, with the highest value occurring in summer; (3) ET showed a downward trend (from 350 to 265 mm) before 2009 and thereafter increased (from 265 to 345 mm); and (4) water use efficiency, indicated by the ratio of Ec to ET, was low in the cropland, with a mean value of 50.9%. Further analysis indicates that decreases in ET are mainly caused by vegetation decreases; in contrast, ecological restriction measures and strict water resource management policies in the middle reaches of the basin led to ET increases. It is concluded that understanding ET and its two components can elucidate the connections between water and human society.
Highlights
The goal of sustainable development is to balance the human-nature equilibrium
It is challenging to achieve this goal because the human-nature system comprises complex interactions among hydrologic systems and climatic, ecological, biophysical, biochemical and socioeconomic systems [1,2]
The hydrologic process is intimately linked with energy exchanges between the atmosphere, ocean, and land, and the hydrologic system determines the spatiotemporal distribution of water resources [3,4], which are necessary for sustaining life on Earth
Summary
The goal of sustainable development is to balance the human-nature equilibrium. it is challenging to achieve this goal because the human-nature system comprises complex interactions among hydrologic systems and climatic, ecological, biophysical, biochemical and socioeconomic systems [1,2]. The hydrologic process is intimately linked with energy exchanges between the atmosphere, ocean, and land, and the hydrologic system determines the spatiotemporal distribution of water resources [3,4], which are necessary for sustaining life on Earth. Under such conditions, quantifying the key hydrologic variables in space is required to provide a deep understanding and a detailed analysis of land surface processes; in turn, this knowledge provides crucial information for water resource management and informs policy decisions to enhance sustainable development [5,6]. An accurate assessment of the characteristics of the spatiotemporal distribution of ET can provide fundamental information for studying the feedback mechanism between vegetation and water [5,8,14]
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