Hydrological connectivity from glaciers to rivers in the Qinghai-Tibet Plateau: roles of suprapermafrost and subpermafrost groundwater

Abstract

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.

Using hydrogeochemical data to trace groundwater flow paths in a cold alpine catchment

“…Our field investigation and drilling work shows that permafrost is mainly distributed in mountainous areas with elevations above 3,500 m a.s.l. (Ma et al, ), and the seasonally frozen layer is mostly confined to the piedmont plain below 3,500 m a.s.l. The result is consistent with the simulation results from Ge () and Zhang et al ().…”

“…The local meteoric water line (LMWL) in the Hulugou catchment was fitted to the equation δ 2 H = 8.5 δ 18 O + 22.6, which was defined by Ma et al (); Figure a). The isotopic concentrations of stream water and groundwater from the seasonally frozen area were plotted on the LMWL; the plot of the groundwater from the permafrost area fell below the LMWL (Figure a).…”

“…The mean annual precipitation is approximately 500 mm, with the majority occurring between June and September (Liu et al, ). The annual potential evaporation is approximately 1,100 mm (Chang et al, ; Ma et al, ), and the mean annual temperature is approximately −3.9°C (Ma et al, ).…”

“…Previous studies have indicated that the thickness of active layer in the permafrost area is 2 m below ground surface (b.g.s.) and the perennially frozen layer extends from 2 m to 20 m b.g.s (Ma et al, ). The suprapermafrost and subpermafrost groundwater has been reported by Ma et al ().…”

“…The east and west tributaries are the two main tributaries of the Hulugou mainstream (Figure ), whose headwaters are fed mainly by glacier‐snow meltwaters, ice lakes, and springs; of these sources, the glacier‐snow meltwaters are the most important (Li et al, ; Ma et al, ; Wang et al, ). These tributaries persist throughout the summer but are intermittently dry during the cold season.…”