Influences of Frozen Ground and Climate Change on Hydrological Processes in an Alpine Watershed: A Case Study in the Upstream Area of the Hei'he River, Northwest China

Abstract

In cold regions, the occurrence of frozen ground has a fundamental control over the character of the water cycle. To investigate the impact of changing ground temperature conditions on hydrological processes in the context of climate change, a distributed hydrological model with an explicit frozen ground module was applied to an alpine watershed in the upstream area of the Hei'he River in the Qilian Mountains, northwest China. After evaluating the base model, we considered scenarios of frost‐free ground and climate change. Results showed that the base model with a frozen ground module successfully captured the water balance and thermal regimes in the basin. When the frozen ground module was turned off, the simulated groundwater recharge and base flow increased by a factor of two to three because surface runoff caused by exceeding infiltration capacities at high elevations, which occurred in the base model, was eliminated. Consequently, the river hydrograph became smoother and flatter, with summer flood peaks delayed and reduced in volume. The annual mean depth where subsurface runoff was generated, was about 2.4 m compared to 1.1 m in the base model. For a warming climate, a combination of increasing evapotranspiration and reducing permafrost area results in smoother and flatter hydrographs, and a reduction in total river discharge. Although our analysis using numerical models has its limitations, it still provides new quantitative understanding of the influences of frozen ground and climate change on hydrological processes in an alpine watershed. Copyright © 2016 John Wiley & Sons, Ltd.

Influences of Topographic Shadows on the Thermal and Hydrological Processes in a Cold Region Mountainous Watershed in Northwest China

“…With parameters properly provided, the model can be applied in areas with different land use types, including bare land, grass land, forest, bush, and crop land. Zhang et al () coupled SHAW into a geomorphologically based distributed hydrological model (GBHM; Yang, ; Yang et al, , , ) and obtained SHAWDHM which was evaluated and used to investigate the influences of ground freezing and thawing on the hydrological processes in a cold and mountainous area (Zhang, Cheng, et al, ). In SHAWDHM, the complex topography in a model cell was lumped into two symmetric hill slopes along a virtual river based on a finer digital elevation model (DEM).…”

Hydrological impacts of near‐surface soil warming on the Tibetan Plateau

“…By contrast, precipitation mainly occurred from June to September and streamflow began to increase after February in the YtzSR and YrSR, so the hydrological recession coefficient 5 was estimated as the ratio of flow in February to October. Baseflow is the minimum water discharge maintained in the river during the dry season, and it often derives from groundwater discharge or other delayed sources such as snowmelt 31 .…”

“…In cold regions, runoff regimes are subject to strong permafrost conditions, because the presence of permafrost layer acts as a barrier to constrain soil water to recharge deeper layers 4,5 . Induced by a warmer climate, widespread degradation has occurred in soil freeze/thaw (F/T) processes on the TP, including an increase in active layer thickness and decrease in permafrost extent 6–8 .…”

Characteristics of Water‐Heat Exchanges and Inconsistent Surface Temperature Changes at an Elevational Permafrost Site on the Qinghai‐Tibet Plateau

“…It generally causes cold ground temperatures at high latitudes and warm and sensitive ones at the midlatitudinal regions with elevational permafrost. Land surface water‐heat exchanges, being affected by the surface characteristics, microtopography, geology, and hydrology, alter the distribution of permafrost at site‐specific, local, or regional scales (Guo et al, ; Romanovsky & Osterkamp, ; You et al, ; Z. Zhang et al, ; Y. Zhang et al, ; Zhao et al, ). The change in hydrothermal processes on the ground surface exerts great influences on the degradation of permafrost, and vice versa (Iijima et al, ; Stiegler et al, ).…”