Spatiotemporal patterns and driving factors of evapotranspiration (natural and artificial) in the Ziya River Basin, China

Abstract

Evapotranspiration (ET) accounts for 60%-70% of terrestrial precipitation. Accurately calculating ET has always been one of the hot issues in ecohydrological research. Watershed ET includes natural ET and artificial ET. Natural ET includes vegetation transpiration, bare land evaporation (the two called land ET) and water surface evaporation. Artificial ET mainly refers to irrigation ET, that is, ET generated by human activities. Estimating total ET is the premise of watershed ET management. In this paper, we used the Penman‒Monteith model to estimate land ET, the Dalton model to estimate water surface evaporation, and the AquaCrop model to estimate ET generated by agricultural irrigation water in the Ziya River Basin from 2005 to 2015. Based on the integrated watershed evapotranspiration model, the effects of driving factors on ET were quantitatively analysed. The results showed that the Penman‒Monteith model, Dalton model and AquaCrop model had high simulation accuracy. The total ET fluctuated between 418.4 and 452.3 mm/yr, and the annual average ET was 437.5 mm/yr. The ET of the main land use types was ranked as woodland (496.7 mm/yr) > arable land (468.9 mm/yr) > grassland (320.0 mm/yr). Spatially, the ET in mountainous areas was lower than that in plain areas. The distribution of ET in the total amount, mountainous and plain areas, woodland, grassland and arable land showed a significant Gaussian distribution. Temporally, the interannual variation was small, and the intra-annual difference was mainly caused by climate factors. The conversion of grassland and woodland into arable land had the greatest impact on the total ET. Temperature, precipitation and leaf area index had a positive impact on ET. The impact of land cover change on ET was more significant than that of climate factors. This study can provide an integrated approach for ET estimation in water resource management and land planning.