Hydrochemical and Stable Isotope Characteristics of Lake Water and Groundwater in the Beiluhe Basin, Qinghai–Tibet Plateau

Jinlong Li,Dahao Wang,Wei Wang,Jie Dong,Jiaqi Li

doi:10.3390/w12082269

Abstract

Thermokarst lakes are a ubiquitous landscape feature that impact the thermal state, hydrological process, ecological environment, and engineering stability of the permafrost. This study established the hydrochemistry and stable isotope (δ18O and δD) variations of lake water and groundwater in a typical basin located in the central Qinghai–Tibet Plateau (QTP) of China. The results showed that most water samples could be classified as slightly alkaline, with high levels of salinity and hardness, while the dominant water types were HCO3-CO3 and Cl types. Natural hydrochemical processes, such as mineral dissolution, cation exchange, and groundwater evaporation, had strong impacts on the groundwater chemistry in this region. Dissolution of halite and carbonate minerals causes the major reactions controlling water chemistry in this basin. Additionally, the calculation of the saturation index (SI) values suggested that aragonite, calcite, and dolomite are saturated, while halite is not. Based on the analysis of the stable isotope characteristics, atmospheric precipitation, groundwater, and meltwater from the permafrost are the major sources of thermokarst lakes. Moreover, the evaporation-to-inflow ratio (E/I) indicated that all of the lakes continuously expanded and rapidly developed. Overall, groundwater is an crucial source of lake recharge and its hydrochemical characteristics also have a certain impact on lake water quality.

Highlights

The Qinghai–Tibet Plateau (QTP), known as the “third pole” of the earth, is experiencing a faster and more sensitive increase in temperatures on account of climate change than other regions at similar latitudes [1]
Are expected be varied complex as a as direct result of global warming, so studies need to be conducted at lake-specific levels to improve a direct result of global warming, so studies need to be conducted at lake-specific levels to improve the comprehensive science-based monitoring programs for adequate assessment of the balance the comprehensive science-based monitoring programs for adequate assessment of water the water balance and and hydrological processes in the this study was conducted in the BLB, which is is hydrological processes in the QTP [6]
Statistical analysis of the major ions is the basis of understanding the hydrochemical characteristics of water [29]

Summary

Introduction

The Qinghai–Tibet Plateau (QTP), known as the “third pole” of the earth, is experiencing a faster and more sensitive increase in temperatures on account of climate change than other regions at similar latitudes [1]. Permafrost degradation in the QTP resulting from global warming in recent decades has considerably affected the hydrological and ecological processes [2]. Numerous studies have emphasized that it has led to variations in hydrological conditions and redistribution of the subsurface water in the QTP [3,4,5]. As a result of global warming and the spread of human engineering, the thickness of the active layers is increasing, while the underlying permafrost is disappearing. In the freezing and thawing process, underground ice undergoes continuous melting and freezing in the permafrost active layer, which reduces the stability of important projects in the QTP. Many geological landscape and disasters, such as thermokarst lakes (Figure 1a), thermokarst collapse (Figure 1b), and thermokarst flow, occur as a result of such transformations

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Conclusion