Cryo‐Hydrogeological Characteristics and Configuration of a Stream‐Talik System in a Discontinuous Permafrost Environment on the Qinghai‐Tibet Plateau

ABSTRACT A comprehensive approach including ground temperature, surface temperature, and hydraulic head monitoring along with electrical resistivity tomography (ERT) surveys was used to investigate the cryo‐hydrogeological characteristics of a complex stream‐talik system in a discontinuous permafrost environment on the Qinghai‐Tibet Plateau (QTP). Insulating properties of the flowing stream water enhance ground heat storage beneath the stream, which significantly delays the freezing of the underlying streambed in fall and early winter. Moreover, discharge of pressurized groundwater in the talik leads to icing, which thickens and spreads during the winter and acts as a thermal buffer. Due to these warm thermal conditions of the streambed, ground temperatures remained above 0 °C at depth all year round, the contours of which delineate a 2‐m‐thick talik beneath the streambed. Moreover, a supra‐permafrost talik and a through‐permafrost talik were identified as zones of low electrical resistivity in the electrical resistivity models derived from the inversion of the ERT data along two survey lines. As it follows the variable width of the stream channel in a warm permafrost environment, the underlying talik develops a complex 3D structure with changing cross‐sectional areas, lying either above or sporadically extending completely through the permafrost. Additionally, where permafrost underlies the talik, temperatures within the talik remain higher than −0.22 °C, which thus remains somewhat permeable, allowing groundwater flow. This stream‐talik and permafrost system creates complex cryo‐hydrogeological responses that can impact local water supply and ecosystem stability.