Permafrost and groundwater on the Qinghai-Tibet Plateau and in northeast China

The areal extent of permafrost in China has been reduced by about 18.6 % during the last 30 years. Due to the combined influences of climate warming and human activities, permafrost has been degrading extensively, with marked spatiotemporal variability. Distribution and thermal regimes of permafrost and seasonal freeze-thaw processes are closely related to groundwater dynamics. Permafrost degradation and changes in frost action have extensively affected cold-regions hydrogeology. Progress on some research programs on groundwater and permafrost in two regions of China are summarized. On the Qinghai-Tibet Plateau and in mountainous northwest China, permafrost is particularly sensitive to climate change, and the permafrost hydrogeologic environment is vulnerable due to the arid climate, lower soil-moisture content, and sparse vegetative coverage, although anthropogenic activities have limited impact. In northeast China, permafrost is thermally more stable due to the moist climate and more organic soils, but the presence or preservation of permafrost is largely dependent on favorable surface coverage. Extensive and increasing human activities in some regions have considerably accelerated the degradation of permafrost, further complicating groundwater dynamics. In summary, permafrost degradation has markedly changed the cold-regions hydrogeology in China, and has led to a series of hydrological, ecological, and environmental problems of wide concern.