Tracing the sources and evaporation fate of surface water and groundwater using stable isotopes of hydrogen and oxygen.

ABSTRACT

Recognizing the origins and movement processes of surface water and groundwater is crucial for understanding hydrochemical genesis, conserving water supplies, and managing water resources. Estimating the source water typically involves identifying the intersection of evaporation line (EL) and meteoric water line. However, there is currently confusion in determining the regional EL and selecting strategies for estimating the source water. This study aimed to explore the source of surface water and groundwater, as well as evaporation effect utilizing stable isotope tracing (δ2H and δ18O). The line-conditioned excess was adopted to differentiate evaporated water and non-evaporated water, then Craig-Gordon model and an analytical framework with Bayesian theory were used to investigate the source of surface water and groundwater and the evaporation influence. The findings revealed that surface water and groundwater in the northern region of the Weihe River suffered more sever evaporation impacts that the south, and the evaporated surface water (7.54 % to 27.34 %) with a wider range of mean evaporation ratio than evaporated groundwater (5.38 % to 8.52 %). Monsoon precipitation is the main contributor to both surface water (contribution ratio 0.46) and groundwater (0.49) sources. This research provides specific information on evaporation and detailed insights into the source water of surface water and groundwater, aiding in understanding the evaporation effect during the hydrological cycle and facilitating the management of regional water resources.