Control of the Interactions Between Stream and Groundwater by Permafrost and Seasonal Frost in an Alpine Catchment, Northeastern Tibet Plateau, China

Abstract

While the individual effects of permafrost and seasonal frost on the interactions between groundwater and surface water have received much attention, few attempts have been made to investigate the effects of permafrost and seasonal frost together on groundwater flow and its interactions with surface water. In this study, hydraulic, chemical, and isotopic data as well as a Bayesian mixing model were employed to investigate the interactions between streams and groundwater, the contributions of groundwater to the mainstream, and their relationships to the distribution of permafrost and seasonal frost in a representative subcatchment in the headwater region of the Heihe River Basin on the northeastern Qinghai‐Tibet Plateau in China. Our results showed that due to the freezing and thawing of recharge water sources and soils, the groundwater flow and stream flux from the permafrost zone to the seasonal frost zone increased during the thawing period, with maximum values in thawed period, and decreased during the frozen period. These variations affected groundwater recharge in the seasonal frost zone, resulting in dynamic changes in the groundwater table and the hydraulic gradient between the recharge and discharge points in the seasonal frost zone during the different freeze‐thaw periods. Correspondingly, the contribution of groundwater to the mainstream discharge decreased from 95% during the frozen period to 80%–90% during the thawing period. It then decreased to ∼40%–60% of the mainstream discharge during the thawed period and increased to ∼70%–90% during the refreezing period. From the permafrost zone to the seasonal frost zone and the catchment outlet, the aquifers in the piedmont plain of the seasonal frost zone play an important role in maintaining streamflows by switching their hydrological functions, that is, slowly releasing groundwater to maintain the streamflow during the frozen period and rapidly transferring the groundwater to mainstream during the thawed period.

Groundwater Plays an Important Role in Controlling Riverine Dissolved Organic Matter in a Cold Alpine Catchment, the Qinghai–Tibet Plateau

“…The uncertainties in the contributions of DOC flux to the main stream (Table S5 in Supporting Information ) were related to the uncertainties in calculating discharge contributions discussed by Ma et al. (2021) and the variability of the DOC concentrations associated with each source. Generally, the contribution of DOC flux from the tributary stream water showed higher uncertainties during the thawing and frozen periods than during the thawed period.…”

“…From the refreezing period to the frozen period, the active layer was frozen, the tributaries stopped carrying water, and the streamflow was sustained solely by groundwater (Chang et al., 2018; Ma et al., 2021). The results of the endmember calculation from April 2015 to September 2016 also indicate the dominance of the groundwater in the seasonally frozen area to DOC flux at the catchment outlet, which could reach as high as 90% (Figure 9).…”

“…The DOM in both the main stream water and groundwater exhibited higher FI values ( p < 0.001) and C4 abundances ( p < 0.001), and lower HIX values ( p < 0.001) than that in the tributary stream water throughout the year, implying a higher proportion of microbial‐derived DOM. Groundwater flowing through the mineral layer in the seasonally frozen area exhibits relatively longer water residence time (Ma et al., 2021), and represents an important source of microbial‐derived DOM. The release of protein‐like organic matter from the microbial activity, and the preferential absorption of aromatic DOM by the mineral layer, significantly alter the DOM chemical properties of groundwater in the seasonally frozen area (Kaiser & Kalbitz, 2012; Parlanti et al., 2000; Williams et al., 2010).…”

“…Due to the coexistence of permafrost and seasonally frozen area, substantial local altitude differences and the occurrence of majority of annual precipitation and glacier melt during summer, Chang et al (2018) and Ma et al (2021) illustrated that hydrological processes in cold alpine areas varied from those in Arctic areas, which could be responsible for the differences in DOM between them, discussed as follows.…”

Critical Role of Groundwater Inflow in Sustaining Lake Water Balance on the Western Tibetan Plateau

“…Groundwater‐flow system on the TP can be conceptualized in three regimes: near‐surface shallow groundwater above permafrost, deeper groundwater below permafrost and groundwater under low‐lying valleys and fault zones (Cheng & Jin, 2013; Ge et al., 2008). Groundwater flow on the TP is usually driven and sustained by the topographic gradient with recharge occurring at high elevations through the infiltration of precipitation and meltwater from snow and ice (Ge et al., 2008; Ma et al., 2021; Y. Yao et al., 2017, 2021). Though limited, studies show that groundwater storage on the TP has increased considerably since the 2000s (Jiao et al., 2015).…”