Abstract
Surface evapotranspiration is a water exchange process between the atmosphere, biosphere, and hydrosphere. Accurate evapotranspiration estimations in arid and semi-arid regions are important for monitoring droughts and protecting the ecological environment. The main objective of this study is to build an evapotranspiration estimation model suitable for an effective scientific and objective evaluation of water consumption in the arid and semi-arid regions of the Xilin River Basin based on comprehensive parameters, including meteorological parameters, vegetation coverage, and soil water content. In this study, the community evapotranspiration model was initially constructed using field data, which was then expanded for applicability to the Xilin River Basin based on Geographic Information System technology and spatial heterogeneity characteristics of remote sensing data; both models were significant at the 0.05 level. The monthly evapotranspiration values in July during 2000–2017 and those from April to September (growing season) during the dry, normal, and wet years were calculated using the model at the basin scale. The evapotranspiration showed a generally increasing trend, which was consistent with the fluctuation trend in precipitation in July during 2000–2017. The trend curve for evapotranspiration was gentle during the growing season in dry years, but steep during wet years. The evapotranspiration was the lowest in April, with negligible spatial variations throughout the Xilin River Basin. During May–July, the evapotranspiration was higher than that in other months, in the following order: upper reaches > middle reaches > lower reaches; this was consistent with the vegetation coverage. The evapotranspiration declined and spatial variations were not evident during August–September. The results of this study provide a reference for evapotranspiration model construction and a scientific basis for evaluating regional water resources and protecting the ecological environment.
Highlights
Surface evapotranspiration (ET), which is the sum of the soil evaporation and plant transpiration, transports moisture from the ground surface to the atmosphere and alleviates net radiation from the surface
Based on Geographic Information System (GIS) and remote sensing (RS) techniques, pixel-by-pixel calculations were performed using the model before determining the monthly ET values in July during 2000–2017 and the monthly ET from April to September during the growing season of dry (2000 and 2007), normal (2011 and 2014), and wet years (2012)
Further analysis of the ET data retrieved from the model and environmental factors in the same period showed that monthly ET in the Xilin River Basin (XRB) was significantly correlated with soil water
Summary
Surface evapotranspiration (ET), which is the sum of the soil evaporation and plant transpiration, transports moisture from the ground surface to the atmosphere and alleviates net radiation from the surface. The dual-source S– W model concurrently considers soil evaporation and vegetation transpiration, but requires many parameters [9], whose accurate acquisition is complicated (such as the canopy stomatal resistance) [8]. The multi-source models exhibit a similar limitation [8], hindering their universal applicability These models are relatively less practical for calculating the actual ET in arid and semi-arid regions owing to the low vegetation coverage. ET is closely related to the vegetation type, leaf area index, vegetation density, plant growth cycle, and soil water content, among other factors [28,29,30,31,32]; the construction of a simple and practical ET inversion model that considers these parameters is important
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