Applicability of different potential evapotranspiration estimation methods in Poyang Lake area

Evapotranspiration is a key component of water resource balance, and accurately estimating evapotranspiration is crucial for rational allocation and utilization of water resources. To gain a deeper understanding on the potential evapotranspiration (ET0) characteristics in Poyang Lake area and the applicability of different ET0 estimation formulas in this region, based on daily meteorological data from the Poyang meteorological station (from 1961 to 2019), we used the multi-year ET0 calculated by the FAO 56 Penman-Monteith method as the reference value to study the temporal variation of ET0 in Poyang Lake area. Additionally, we assessed the applicability of three combination methods, four radiation-based methods, and two temperature-based methods across various scales. Furthermore, path analysis was employed to explore the causes of ET0 variation. The results showed that: ① Over the past 59 years, the average annual ET0 value in the lake area was 974.49 mm, exhibiting a non-significant downward trend (-2.68 mm/10 a), together along with the significant warming trend, which confirms the presence of the "evaporation paradox" phenomenon in this region. ② The combination methods showed the best applicability in the region, followed by the radiation-based methods. Among the radiation-based methods, the Makkink and FAO 24 Penman methods had the best applicability, while the Mc Cloud method showed the worst applicability. ③ The five meteorological factors were ranked in a descending order of their influence on ET0 as follows: net radiation > mean temperature > sunshine duration > vapor pressure deficit > mean wind speed at 2 m height. Net radiation was the most essential meteorological factor influencing ET0 variation in the region, followed by temperature. This study provides scientific evidence for the rational allocation and regulation of water resources in Poyang Lake region.