An effective evapotranspiration estimation scheme based on statistical indicators for sustainable environments in humid and semi-arid area of Khyber Pakhtunkhwa, Pakistan

Abstract Reference evapotranspiration (ETo) is critical for irrigation design and water management in rainfed irrigated agriculture. The Penman-Monteith (FAO-56(PM)) equation was demonstrated to be the most reliable adaptive a wide range of humid semi-arid climates. However, it requires several environmental parameters (e.g., wind speed, solar radiation), rarely available developing countries. Therefore, numerous temperature-based formulas have been designed address this issue various environments. Their calibration validation against local climate frequently lead increases performance. We revised Hargreaves exponent (EH) substituted value (0.16) original (0.5). modified formula enhances ETo predictions with mean absolute error ranging from (0.791) mm per day Balakot (2.36) Risalpur, averaging (3.797) day, as compared Hargreaves-Samani (16.827) day. In general, all selected models showed high accuracy. appeared give promising results. It ranked first (50%) whole area based on standard estimate estimating Khyber Pakhtunkhwa. Additional research must conducted determine study's relevance other regions.