An Analysis of Surface Water–Groundwater Interactions Based on Isotopic Data from the Kaidu River Basin, South Tianshan Mountain

Abstract

The unique climate conditions and water source composition in the Tianshan Mountain provide a good experimental site for verifying the relationships between water resources and climate change on a larger scale. With the help of water isotopes (D, 18O), a more reliable conceptual model of groundwater systems can be constructed on both local and regional scales, especially in areas that are susceptible to climate change and under pressure from intensive human activities. In this paper, we present δ18O, δD, d-excess, RWLs and altitude effects of river water and groundwater based on the data derived from our network of stable isotope sampling sites along the Kaidu River. Stable isotope mass balance was applied to study the interactions between groundwater and surface water and to quantify the recharge proportions between bodies of water in typical regions. The results showed that the Kaidu River is composed of precipitation, ice and snow melt, baseflow and groundwater. The percentage of groundwater increased with the distance between upstream (the runoff producing area) and the leading edge of the glacier. The two recharge areas are the spring overflow from the mountain area to the alluvial layer of the inclined plain and the leading edge of the alluvial plains to areas with fine soil. The groundwater recharge ratio is about 23% in high mountain areas but 46% or more in the middle and lower reaches. These results generated a more comprehensive understanding of the hydrological cycle of inland rivers in arid regions.