Hydrochemical and stable isotopic spatiotemporal variation characteristics and their environmental significance in the Kashi River Mountain Area of Ili, Xinjiang, China

The supply sources of a water resource in arid area can be determined through analysis of the hydrochemical and stable isotopic characteristics of runoff in an alpine glacier river basin. Using mathematical statistical analyses, Piper diagrams, and Gibbs diagrams, this study analyzed the spatiotemporal variations of the hydrochemistry and the stable hydrogen and oxygen isotopes of the Kashi River in Ili (Xinjiang, China) to investigate their characteristics and environmental importance. Runoff samples were collected in the mountainous area of the Kashi River from December 2017 to November 2018. Results showed that the runoff water type of the Kashi River is Ca2+–HCO3− and the spring water type is Ca2+–HCO3−–SO42−. The main factors controlling the hydrochemical composition of runoff were rock weathering. Under the influence of supply sources and water conservancy facilities, the hydrochemistry and stable isotopic characteristics of the runoff showed evident spatiotemporal variation. The hydrochemical and stable isotopic values of runoff in winter and spring were lower and more consistent in comparison with those in summer and autumn. The characteristics of the spatial variations of hydrochemical and stable isotopic values in runoff differed with elevation. The supply sources in the Kashi River in different seasons were determined by analyzing the temporal variation characteristics of the hydrochemistry and stable isotopes of runoff.