Stable isotope evidence confirms lakes are more sensitive than rivers to extreme drought on the Qinghai-Tibet Plateau, China

Abstract

The extreme drought event that occurred in China at the beginning of summer 2022 has caused widespread societal concern. The hydrogen and oxygen stable isotope data collected in the summer of 2022 on the eastern Qinghai-Tibet Plateau (QTP) were used here to quantify the responses of the lakes and rivers to extreme drought. The results showed that the evaporation fractionation of lake water was the strongest (lc-excess: −21.62‰), the evaporation fractionation of thermokarst lake water was the second strongest (lc-excess: −15.33‰), and the evaporation fractionation of river water was weak (lc-excess: −0.30‰) during the extreme drought event. Compared to the previous years, the strongest isotopic enrichment of surface water during the extreme drought occurred in lake water (E(δ18O): 58.61%), followed by thermokarst lake water (E(δ18O): 48.18%), while that in river water was weak (E(δ18O): 9.41%). Solar radiation was the main environmental factor controlling isotopic variations among different surface water. The ratios of evaporation to inflow of surface water caused the greatest isotopic enrichment to be found in lakes. Therefore, the occurrence of extreme drought events resulted in the lake water isotopic signal being the strongest evaporation enrichment reaction. The extreme drought event that occurred in the summer of 2022 intensified the evaporation enrichment of different surface waters on the eastern QTP. The results provide new insights into the surface water feedback climate change over the QTP.