Assessment of Reference Evapotranspiration Under Climate Change Conditions: Method Comparison and Practical Applications

УДК: 551.58:551.577:631.6:504.062 ASSESSMENT OF REFERENCE EVAPOTRANSPIRATION UNDER CLIMATE CHANGE CONDITIONS: METHOD COMPARISON AND PRACTICAL APPLICATIONS Daulet Gulomov Assistant, National Research University "Tashkent Institute of Irrigation and Agricultural Mechanization Engineers" (TIIAME), Tashkent, Uzbekistan Baxodirjon Amanov Associate Professor, PhD, National Research University "Tashkent Institute of Irrigation and Agricultural Mechanization Engineers" (TIIAME), Tashkent, Uzbekistan E-mail: d.gulomov@tiiame.uz https://doi.org/10.5281/zenodo.19382787 Abstract: This study provides a comprehensive evaluation of methods for estimating reference evapotranspiration (ET₀) under climate change conditions. The analysis compares several widely used approaches, including the Hargreaves, Turc, Blaney–Criddle, and FAO-56 Penman–Monteith methods, as well as the satellite-based Manna application. Meteorological data from the Tuyabog'iz meteorological station located in the Tashkent region of Uzbekistan were analyzed for the period 2021–2023. The methods were assessed in terms of estimation accuracy, data requirements, and their suitability for application under local arid climatic conditions. The results indicate that the PM-CROPWAT method estimated seasonal reference evapotranspiration at 935.68 mm, whereas the Manna application produced a value of 706.60 mm, corresponding to a difference of −24.5%. The Hargreaves and Turc methods significantly overestimated ET₀ values by approximately +87% and +77%, respectively. A strong statistical relationship was observed between the monthly values obtained from Manna and CROPWAT, with a coefficient of determination of R²=0.913. The findings demonstrate that the FAO CROPWAT 8.0 software represents an effective tool for the practical calculation of reference evapotranspiration and irrigation scheduling. The results of this research contribute to improving water resource management and optimizing irrigation practices under conditions of increasing climatic variability. Keywords: reference evapotranspiration, climate change, Penman–Monteith method, Hargreaves method, satellite data, CROPWAT, irrigation scheduling.