Abstract: Accurate estimation of evaporation from small water bodies is critical for addressing water resource losses induced by global climate change. Based on hydrogen and oxygen stable isotope data and meteorological observations collected from a fish pond in Anhui Province during 2020-2022, we calculated the monthly evaporation from the pond using a stable isotope mass balance model and the eddy covariance (EC) method. With the EC observations as a reference, we evaluated the applicability of different parameterization schemes for kinetic fractionation. The results showed that monthly evaporation from the fish pond exhibited seasonal variability: summer (99.6±37.3 mm) > spring (89.4±26.5 mm) > autumn (58.7±21.7 mm) > winter (20.6±4.5 mm). The results of the isotope mass conservation model based on different isotopes and parameterization schemes were generally consistent with the observations. The applicability of deuterium (²H) was better than that of oxygen-18 (¹⁸O) in summer and autumn, while ¹⁸O performed better in spring and winter. Overall, ²H showed better performance. Among different parameterization schemes, the ocean-based scheme was generally superior to the lake-based scheme. The localized parameterization scheme based on ¹⁸O and developed using pond observation data (Pearson correlation coefficient=0.85, root mean square error=18 mm) outperformed both the traditional lake-based and ocean-based parameterization schemes. These findings provide important theoretical support and methodological references for enhancing the accuracy and reliability of stable isotope techniques in calculating evaporation from small water bodies.

Key words: isotopic mass balance, evaporation, kinetic fractionation coefficient, eddy covariance, small water body