Estimation and Analysis of Irrigation Water Use Efficiency in Multi-Source Irrigation Areas of Arid Regions Based on the SEBS Model

Accurate quantification of irrigation water use efficiency (IWUE) is essential for sustainable oasis agriculture in arid regions with multi-source water supply. Examining the Yongji Irrigation Area of the Hetao Irrigation District, this study developed a Surface Energy Balance System (SEBS)-based evapotranspiration (ET) model for the area using Landsat-8 imagery and 2023 meteorological data. Model performance was evaluated against ground-based observations. SEBS-derived ET was coupled with a regional water balance approach to estimate IWUE under multi-source irrigation and compared with the conventional canal water balance method. The main findings are as follows: (1) in 2023, remotely sensed ET totaled 5.4×10⁸m³, corresponding to an IWUE of 0.426; (2) SEBS-retrieved daily ET agreed well with in situ observations at the Linhe Meteorological Station on seven dates between April and October 2023, with a coefficient of determination R² = 0.816 , root-mean-square error (RMSE) of 0.714 mm/day, mean absolute error (MAE) of 0.703mm/day, and bias of −0.337mm/day, confirming that SEBS reliably captures daily ET dynamics in the Yongji Irrigation District; (3) the SEBS-based IWUE differed by 6.33% from the traditional canal water balance estimate (0.455), suggesting good consistency between the two approaches. These findings indicate that SEBS-based remote sensing can provide spatially explicit, operational assessments of irrigation efficiency and support precision water resources management in arid and semi-arid agricultural regions.