Tugba Yildirim, Şerafettin Aşık
Abstract Spatially explicit and temporally resolved information on actual evapotranspiration (ET a ) is essential for understanding crop water use and supporting irrigation water management and water allocation decisions at the basin scale. This study evaluates the relationship between satellite‐derived daily and monthly ET a and crop evapotranspiration (ET c ) for citrus ( Citrus reticulata ), grape ( Vitis vinifera ), and olive ( Olea europaea ) crops in the Seferihisar–Kavakdere Valley, Turkiye. ET a was estimated for the May–October periods of 2013 and 2014 using Landsat 8 OLI–TIRS imagery and the surface energy balance algorithm for land (SEBAL). ET c was calculated based on the ASCE–EWRI Penman–Monteith reference evapotranspiration (ET₀) using meteorological data from the Seferihisar station and crop‐specific coefficients. The coefficient of determination ( R 2 ) between daily ET a and ET c ranged from 0.73 to 0.85 across crops and years, indicating consistent seasonal behavior between satellite‐based and meteorological estimates. Relative evapotranspiration (RET), defined as the ratio of ET a to ET c , varied between 0.53 and 0.95 in 2013 and 0.45 and 0.87 in 2014, reflecting differences in water availability and irrigation adequacy during the growing season. Monthly ET a and ET c values peaked in July for all crops, corresponding to maximum atmospheric demand. The results demonstrate that SEBAL effectively captures spatial and temporal evapotranspiration patterns in a Mediterranean agricultural basin dominated by perennial crops. The integration of ET a and RET analyses provides practical insights into seasonal water stress and irrigation performance, supporting basin‐scale water management and irrigation planning in data‐scarce regions.