Estimation of evaporation loss from an irrigation reservoir in arid region using effective isotopic fractionation method

Accurate estimation of evaporation loss from open water bodies is important for improving agricultural water management, especially in arid and semi-arid regions. However, the conventional isotopic fractionation methods such as the kinetic and equilibrium methods suffer from accuracy problems in estimating evaporation loss. In this study, an improved fractionation method, namely the effective isotopic fractionation method was proposed to estimate the evaporation loss from an irrigation reservoir by incorporating the local atmospheric isotope value into the isotopic fractionation factor. Indoor and outdoor evaporation experiments were conducted to validate the estimation accuracy of the proposed method based on the experimental and calculation results for three isotopic methods. The results showed that the relationship between δD and δ¹⁸O of the experimental evaporation line was consistent with the actual evaporation line. Evaporation loss was positively correlated with temperature, and negatively correlated with humidity. The estimation results showed that the effective isotopic fractionation method had a higher goodness of fit with the monitored data than the kinetic and equilibrium methods, which was further validated by the results of the outdoor evaporation experiment. Furthermore, the change in humidity had a greater effect on the effective fractionation method than that on the other two methods, while the kinetic and equilibrium methods were more sensitive to the change in temperature. This study suggests that the effective isotopic fractionation method provides a more reliable approach to improve the accuracy of evaporation estimation by incorporating the local atmospheric isotope value into the evaporation fractionation of hydrogen and oxygen isotopes. The present study provides new insights into the accurate estimation of evaporation loss from open water bodies using the isotopic fractionation method, which can improve water resources management in arid agricultural regions.