Abstract. The roles of subsurface groundwater flow in the hydrological cycle within the alpine area characterized by permafrost and/or seasonal frost are poorly known. We studied the role of permafrost in controlling groundwater flow and the hydrological connections between glaciers in high mountain and river in the low plain with hydraulic head, temperature, geochemical, and isotopic data. The study area was a catchment in the headwater region of the Heihe River in the northeastern Qinghai-Tibet Plateau. The groundwater in the high mountains mainly occurs as suprapermafrost groundwater, and in the moraine and fluvio-glacial deposits on the planation surfaces of higher hills suprapermafrost, intrapermafrost, and subpermafrost groundwater co-occur. Glacier and snow-meltwater are transported from the high mountains to the plain through stream channels, slope surfaces, and supra- and subpermafrost aquifers. Groundwater in the Quaternary aquifer under the piedmont plain is recharged by the lateral inflow from permafrost groundwaters and the infiltration of streams, and is discharged as baseflow to the stream in the north. Groundwater maintained stream flow over the cold season and significantly contributed to the stream flow during the rainy season. 3H and 14C data indicated that the age of supra- and sub-permafrost groundwater, and groundwater in Quaternary aquifer of seasonal frost zone, ranges from 30–60 years. Two proposed mechanisms contribute to seasonal variation of the aquifer water-conduction capacity: (1) surface drainage through the stream channel during the high-flow period, and (2) subsurface drainage to an artesian aquifer confined by stream icing and seasonal frost during the cold season.

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