Environmental significance and hydrochemical processes at a cold alpine basin in the Qilian Mountains

Abstract

Isotope geochemistry of precipitation, river water, well water and spring water in the Babao River basin, China, during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring. The δ18O and δD values of precipitation and spring water displayed a clear altitude effect. Water from the main stream and tributaries displayed a converse altitude effect in the summer-wet season. The isotopic composition of the various water sources was not well correlated with elevation during the winter-dry season. The spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs, evaporation and variable flow. An end-member mixing model used for hydrograph separation indicated that in the summer-wet season, the Babao River water was recharged by precipitation (71.9 %), spring water (11.7 %) and well water (16.4 %), whereas the winter-dry season recharge was sourced from spring water (28.2 %) and well water (71.8 %).