• 标题：Suprapermafrost groundwater flow and exchange around a thermokarst lake on the Qinghai–Tibet Plateau, China
• 关键词：Qinghai–Tibet Plateau; Suprapermafrost groundwater; Thermokarst lake; Water balance
• 作者：

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The dynamics of suprapermafrost groundwater regulate hydrological processes, including the fate and transport of carbon and nutrients, suitability of aquatic habitats, and evolution of permafrost in Arctic, boreal, and high-altitude regions. Nevertheless, relatively few studies have focused on these dynamics on the Qinghai–Tibet Plateau (QTP). In this study, soil hydraulic conductivities, saturated thicknesses, and related hydrological processes were observed in situ around a typical thermokarst lake during the warm season. The results showed that the water table in the active layer fluctuated markedly from June to October and at depths of up to 1.0 m. The discharge of suprapermafrost groundwater was often <0.1 m 2 d ?1 , which was attributed to the thin aquifer and low permeability of the active layer. Groundwater fluxes were controlled by the freeze–thaw cycle and local factors, and were altered by rainfall events and evapotranspiration. The contributions of suprapermafrost groundwater to the thermokarst lake water were often <1.4 mm d ?1 , and were greater in the late warm season. Moreover, surface runoff in initial warm season was the dominant water resource in some open parts of the lake, and the frequent exchange between surface runoff and lake water accelerated the degradation of the permafrost beneath the lake. These findings provide insights into the role of suprapermafrost groundwater in regional hydrological cycles and the evolution of thermokarst lakes on the Qinghai–Tibet Plateau.