干旱区生态环境知识资源中心

We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios (delta D and delta O-18) of precipitation, spring, river, and melt water. The similar seasonality in precipitation delta O-18 at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of delta O-18 and d-excess for precipitation at Yeniugou and Urumchi, which showed more positive delta O-18 and lower d-excess values in summer and more negative delta O-18 and higher d-excess values in winter, indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas of northwestern China, water is intensively recycled. Temporal changes in delta O-18, delta D, and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example, there were similar trends for delta D, delta O-18, and d-excess of precipitation and river water from June to September, similar delta O-18 trends for river and spring water from December to February, and similar trends for precipitation and runoff volumes. However, there were significant differences in delta O-18 between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September, whereas the supply of surface runoff in winter was from base flow (as spring water), mostly with a lower runoff amount.