Spatio-temporal variation of stable isotopes of river waters, water source identification and water security in the Heishui Valley (China) during the dry-season

Spatial variations of δD and δ¹⁸O among seven tributaries and their water sources were investigated in the Heishui Valley of the Yangtze River, China during the dry-season in 2004. A one-way ANOVA (analysis of variation) test showed that both δD (p?18O (p?=?0.045) spatially varied among the seven tributaries. The plot of δ¹⁸O versus δD for the river water collected at different locations showed that isotopic fractionation occurred during the snow and glacial melting process. The depleted δ¹⁸O and δD in the tributary waters distributed above the local meteoric water line (LMWL) suggested that the glacial and early snowpack meltwater largely recharged these streams during the early spring. The meltwater was isotopically distinguishable from the precipitation and river water, which had been evaporated during warmer and drier times. If glaciers and snow accumulation diminish with future climate warming, the recharge of these tributaries’ baseflow will decline and the security of the water resource in this watershed will be threatened.