Contribution from frozen soil meltwater to runoff in an in-land river basin under water scarcity by isotopic tracing in northwestern China

Cryosphere meltwater has been recognized as an important source of local water resources. However, there are few assessments on the contribution from frozen soil meltwater. In this study, we quantify the fraction from frozen soil meltwater and glacier snow meltwater to runoff in Shiyang River, an in-land river basin of northwestern China, where glaciers were disappearing and frozen soil was in degradation. A large number of samples for precipitation, surface water, groundwater, frozen soil meltwater and glacier snow meltwater have been collected and analyzed for their isotopic compositions. Results indicated that runoff was mainly generated from the cryosphere belt, and it was found that frozen soil meltwater was responsible for 20%, on average, of the outlet river water during flood season in the basin. The contribution rates from frozen soil meltwater to the outlet river runoff changed among the seven sub-basins. The results confirmed that frozen soil meltwater has played an important role in runoff of in-land river basins, and evaluating its influence on the hydrological process under a climate warming scenario is of great significance.