Spatiotemporal variations in evapotranspiration and its driving factors in the Yellow-River Irrigation District in Ningxia

ZHANG Xinxin; HUANG Yejian; CHEN Xinguo; HUANG Quanzhong; LI Min

doi:10.13522/j.cnki.ggps.2025104

Abstract：[Background and Objective]Accurate and timely estimation of evapotranspiration(ET)in an irrigation districts is critical for rationally allocating water resources and improving irrigation efficiency.Understanding the spatiotemporal dynamics of ET and its driving factors is essential for optimizing water management.In this paper,we analyzed the spatiotemporal variations of ET and identified its main driving factors in the Yellow River Irrigation District of Ningxia.[Method]The surface energy balance algorithm for land(SEBAL)model was used to estimate the ET in the irrigation districts from 2000 to 2022.Its accuracy was validated against the results calculated using the Penman-Monteith(P-M)model and the water balance method.Mann-Kendall trend tests and coefficients of variation were used to analyze the spatiotemporal variations of ET,and correlation and regression analyses were used to assess the influence of key environmental factors on ET.[Result]① The SEBAL model was accurate,and the R2 between its results and those calculated from the P-M model was 0.89.Compared to those calculated from the water mass balance method,the average relative error of the SEBAL model was 10.65%.② The average annual evapotranspiration in the irrigation districts was 640.3 mm/a,and the interannual ET increased to a peak in July and the then declined.③ Spatially,ET in the irrigation district was low in the North,high in the centre and and moderate in the South.ET in different vegetation types was ranked in the order of water body＞farmland＞construction land＞grassland＞bare land.④ The correlation between evapotranspiration and vapor pressure deficit was the strongest,with an average correlation coefficient of 0.43 and a regression coefficient of 0.38.[Conclusion]From 2000 to 2022,the evapotranspiration in the Yellow River Irrigation District of Ningxia increased,with vapor pressure deficit being the main driving factor.