Change in frozen soils and its effect on regional hydrology, upper Heihe basin, northeastern Qinghai–Tibetan Plateau

Abstract

Abstract. Frozen ground has an important role in regional hydrological cycles and ecosystems, particularly on the Qinghai-Tibetan Plateau (QTP), which is characterized by high elevations and a dry climate. This study modified a distributed, physically based hydrological model and applied it to simulate long-term changes in frozen ground its the effects on hydrology in the upper Heihe basin, northeastern QTP. The model was validated against data obtained from multiple ground-based observations. Based on model simulations, we analyzed spatiotemporal changes in frozen soils and their effects on hydrology. Our results show that the area with permafrost shrank by 8.8 % (approximately 500 km 2 ), predominantly in areas with elevations between 3500 and 3900 m. The maximum depth of seasonally frozen ground decreased at a rate of approximately 0.032 m decade −1 , and the active layer thickness over the permafrost increased by approximately 0.043 m decade −1 . Runoff increased significantly during the cold season (November-March) due to an increase in liquid soil moisture caused by rising soil temperatures. Areas in which permafrost changed into seasonally frozen ground at high elevations showed especially large increases in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to changes in frozen soils, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The groundwater storage showed an increasing trend, indicating that a reduction in permafrost extent enhanced the groundwater recharge.

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

“…In contrast to previous studies regarding permafrost hydrology on the TP, 8,38 our study showed the contrasting hydrological responses to near‐surface warming related to permafrost coverage fraction on the TP. Our comparison and analyses suggested that permafrost coverage fraction should be taken into account when examining potential variations in the hydrology and water resources on the TP related to climate warming.…”

“…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 . As a result, the permeability of soil layer becomes higher with the lowering permafrost table, which can cause an increase in storage capacity of soil water and thus often lead to a larger contribution of groundwater to streamflow during winter months 9,10 .…”

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

“…As the main water-producing regions of the Heihe River, the headwater catchments provide large volumes of water for the residential, agricultural, and industrial use in the downward reaches. Recently, more studies have been conducted in the headwater catchments of the Heihe River, and these studies have focused on the water balance and surface runoff generation process (Chen et al, 2007;Feng, Liu, Su, Zhang, & Si, 2004;Gao et al, 2018;Li et al, 2014;Wang et al, 2009;Yang et al, 2011;Yao et al, 2015;Zhu, Su, & Feng, 2008). For example, Wang et al (2009) indicated that 80.2% of the annual mountainous runoff originated in the alpine permafrost-snow-ice zone, that is, in areas with elevations above 3,600 m above sea level (a.s.l.).…”

“…Li et al (2014) suggested that 68% of recharge in the Hulugou catchment was from precipitation, and the cryosphere contributed to almost one third of the outlet runoff according to hydrogeochemical and isotopic data. The simulation results from Gao et al (2018) showed that 8.8% of the permafrost areas had degraded into seasonally frozen ground in the upper Heihe River basin from 1971 to 2013; additionally, runoff increased significantly during the cold season (i.e., November to March).…”

Simulation of soil thermal dynamics using an artificial neural network model for a permafrost alpine meadow on the Qinghai–Tibetan plateau

“…Several different techniques are used to simulate the soil thermal dynamics of permafrost. Additionally, a wide range of numerical models, such as the simultaneous heat and water (SHAW) model, geomorphology‐based eco‐hydrological model (GBEHM), and Geophysical Institute Permafrost Laboratory model version 2 (GIPL2), are applied to numerically simulate temperatures at different depths in the soil or rock of permafrost; these models can be successfully applied with simulated ground temperatures. However, the numerical solutions for the soil thermal dynamics of permafrost in physical process‐based models are commonly obtained by solving finite difference equations; these equations require a large number of input parameters, such as temperature, radiation, precipitation, surface reflectivity, snow information (thickness, bulk density, etc.…”