Links between seasonal suprapermafrost groundwater, the hydrothermal change of the active layer, and river runoff in alpine permafrost watersheds

• Main Authors: Qin, Jia, Ding, Yongjian, Han, Tianding, Shi, Faxiang, Zhao, Qiudong, Chang, Yaping, Cui, Junhao
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; permafrost
• Online Access: https://doi.org/10.5194/egusphere-2023-1394; https://noa.gwlb.de/receive/cop_mods_00067630; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00066079/egusphere-2023-1394.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1394/egusphere-2023-1394.pdf

The seasonal dynamic of suprapermafrost groundwater significantly affects runoff generation and concentration in permafrost basins and is a leading issue that must urgently be addressed in hydrological research in cold and alpine regions. In this study, the seasonal dynamic process of the suprapermafrost groundwater level (SGL), vertical gradient changes of soil temperature (ST) and moisture content in the active layer (AL), and river level changes were systematically analyzed at four permafrost watersheds in the Qinghai–Tibet Plateau using comparative analysis and the nonlinear correlation evaluation method. How freeze–thaw processes impact seasonal SGL, and the links between SGL and surface runoff, were also discussed. The SGL process in a hydrological year can be divided into four periods: (A) a rapid falling period (October–middle November), (B) a stable low-water period (late November–May), (C) a rapid rising period (approximately June), and (D) a stable high-water period (July–September), which synchronously respond to seasonal variations in soil moisture and temperature in the AL. The characteristics and causes of SGL changes varied significantly during the four different periods. The freeze-thaw process of the AL has crucial regulatory effects on SGL and surface runoff in permafrost watersheds. During Period A, with rapid AL freezing, the ST had a dominant impact on the SGL. In Period B, the AL was entirely frozen because of the stably low ST, and the SGL dropped to the lowest level with small changes. During Period C, ST in the deep soil layers of the active layer (below 50 cm depth) significantly impacted the SGL (nonlinear correlation coefficient R2>0.74, P<0.05), whereas the SGL change in the shallow soil layer (0–50 cm depth) had a closer relationship with soil moisture content. Rainfall was the major cause for the stable high SGL during Period D. In addition, the SGLs in Periods C and D were closely linked to the retreat and flood processes of river runoff. The SWL contributed approximately ...