Permafrost, as a unique geological phenomenon in the Qinghai-Xizang Plateau and other high cold regions, its water-retaining effect makes the runoff generation processes and convergence in the frozen watershed significantly different from that in the non-frozen region.

Therefore, it is of great significance to deeply understand the change rule of permafrost and its influence on hydrological process for promoting the study of hydrology and water resources in alpine region.

A research team at the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences (CAS) quantitatively assessed the hydrological connections between soil water in the permafrost active layer, water above the frozen layer, and surface runoff using long-term data from multiple Qinghai-Xizang Plateau sites.

This work was published in Hydrology and Earth System Science and Catena.

The results show that the freeze-thaw changes of permafrost active layer have a direct impact on the water interaction and transformation relationship of "precipitation -- soil water -- permafrost water -- surface runoff" in the basin, and this impact varies according to the different underlying surfaces of alpine vegetation.

It is found that there is a high correlation between suprapermafrost groundwater and river runoff processes. Statistical analysis of observational data from typical small watersheds revealed that suprapermafrost groundwater contributes 57% to 65.8% of the variability in river runoff. This finding highlights the critical role of permafrost water in the hydrological cycle of the basin.

In addition, the study also found that landscape zones such as cold deserts, glaciers, and alpine meadows are the most important runoff-generating areas in the northwestern alpine permafrost watersheds. For example, more than 95% of the annual runoff in the upper Shule River originates from glaciers, alpine meadows and cold desert landscapes.

The simulation results indicate that permafrost degradation will have a significant impact on watershed runoff. Specifically, permafrost degradation will reduce flood runoff and increase dry season runoff to some extent, and this effect varies significantly by landscape type.

The study not only revealed the influence of freeze-thaw changes in the active layer of permafrost on the hydrological processes of the basin, but also quantified the significant contribution of water from the frozen layer to the change in river runoff, providing a new scientific basis for the management of water resources in the basin.