Mapping the spatial variability of hydrogen and oxygen isotopic compositions in Chinese lake water: Patterns and drivers

While current studies on hydrogen and oxygen isotopic compositions (δDlw and δ18Olw) in Chinese lakes have predominantly focused on individual water bodies, a critical gap remains in large-scale spatial analysis, limiting our understanding of regional variations and common hydrological controls across different climate regimes. To address this, we conducted a comprehensive study analyzing δDlw and δ18Olw from 131 lakes across China, combined with published data from 150 additional lakes, generating the first nationwide maps that reveal pronounced spatial heterogeneity in lake water isotopes. Remarkably, 36 lakes in multiple studies show consistent δDlw and δ18Olw values despite temporal and spatial sampling differences, validating robust cross-lake comparisons. Our results indicate distinct regional patterns: lakes in arid western/northern regions exhibit greater isotopic differences between lake water and annual average precipitation, lower d-excess values, and higher evaporation-to-inflow (E/I) ratios, indicating strong evaporative enrichment. In contrast, lakes in humid eastern/southern regions show smaller isotopic differences, higher d-excess, and lower E/I values, suggesting their isotopic signatures primarily reflect precipitation inputs. Notably, some lakes on the Tibetan Plateau, Inner Mongolia, and Yunnan-Guizhou Plateau display more negative δDlw and δ18Olw values than local precipitation, which may indicate dominant recharge from glacial meltwater and/or groundwater. These findings highlight the essential need to differentiate evaporation effects and recharge sources when interpreting lake water isotopes, particularly across diverse climatic zones.