Satellite-based thermal infrared imaging for evapotranspiration estimation in irrigated agricultural systems

Evapotranspiration represents the dominant consumptive use of water in irrigated agriculture, yet its spatial and temporal variability is rarely monitored with sufficient detail for modern water accounting and irrigation scheduling. This article evaluates satellite-based thermal infrared imaging as a basis for mapping actual evapotranspiration in irrigated systems. A workflow integrating thermal infrared surface temperature, vegetation indices, microwave-derived soil moisture and reference evapotranspiration was implemented for mixed cropping schemes in semi-arid irrigation districts. Contextual surface temperature–vegetation index models, soil moisture constraint functions and ensemble data assimilation were used to derive daily actual evapotranspiration at field scale and to aggregate values to management and basin units. Model outputs were validated against eddy covariance measurements and water balance estimates, and were linked to indicators of irrigation performance and unreported water use. Results demonstrate that satellite thermal infrared imaging can provide consistent, spatially explicit evapotranspiration estimates suitable for both farm-level management and regional water valuation.