Hydrochemical regime and its mechanism in Yamzhog Yumco Basin, South Tibet

Abstract

The hydrochemistry of alpine lakes reflects water characteristic and its response to climatic change. Over 300 water samples had been collected from 52 sites of 5 lakes and 7 inflowing rivers in the Yamzhog Yumco Basin, South Tibet, during 2009-2014, basing which the hydrochemical regime and its mechanism were analyzed along with the adoption of hydrological investigations in 1979 and 1984 as well. Results revealed that the waters were hard with weak alkalinity for the Yamzhog Yumco Basin. Most of them were fresh, and the rest were slightly saline. The hydrochemical types of 5 lakes (i.e., Lake Yamzhog Yum Co, Puma Yum Co, Bajiu Co, Kongmu Co, and Chen Co) were SO 4 2-HCO 3-Mg 2+-Na + , HCO 3-SO 4 2-Mg 2+-Ca 2+ , SO 4 2-Mg 2+-Na + , SO 4 2-HCO 3-Ca 2+ , and SO 4 2-Na +-Mg 2+-Ca 2+ , respectively. As for rivers, HCO 3 and SO 4 2were the major anions, and Ca 2+ was the dominant cation. Lake Yamzhog Yum Co, the largest lake in the basin, exhibited remarkable spatial variations in hydrochemistry at its surface but irregular changes with depth. The weathering of evaporates and carbonates, together with evaporation and crystallization, were the major mechanisms controlling the hydrochemistry of waters in the Yamzhog Yumco Basin. Global warming also had significant impacts on hydrochemical variations.

Hydrochemical characteristics and controlling factors of natural water in the border areas of the Qinghai-Tibet Plateau

“…The Gibbs model plot shows that the rock weathering controls the main hydrochemical composition in the QT border areas ( Figure 5), basically consistent with the previous study of rivers on the QT (Zhu et al, 2010;Yao et al, 2015;Zhe et al, 2017).…”

“…The mEq ratio of Na + to HCO 3 − (Figure 6f) in most of the water samples is less than 1, while the mEq ratio of Na + to SO 4 2− (Figure 6g) in the western and northeastern border area water samples is approximately equal to 1, suggesting that the dissolution of sulfate minerals (e.g., mirabilite) may be among the sources of Na + in the water samples of western and northeastern areas (Zhe et al, 2017). Meanwhile, the mEq ratio of Na + to SO 4 2− (Figure 6g) in the southern area water samples is less than 1.…”

“…Meanwhile, the mEq ratio of Na + to SO 4 2− (Figure 6g) in the southern area water samples is less than 1. Therefore, the Na + in the southern border area water samples may originate from silicates (Zhe et al, 2017). Generally, the ratio of Na + +K + to Cl − is equal to 1 when the dissolution of evaporites plays a major role in hydrochemical compositions (Gibbs, 1970).…”

“…This will further affect the environment of the plateau and its surrounding areas, changing the environment and hydrochemistry of the local natural water, which in turn will affect the production and life of local farmers and herdsmen. In recent years, research regarding the water chemistry on the QT has focused on the major rivers and lakes and their catchments, including Yarlung Zangbo (Sarin and Krishnaswami, 1984;Wang, 2016), Senge Zangbo (Li et al, 2012;Wang et al, 2012), Three River Resource areas (Deng, 1988;Wu et al, 2008;Cao, 2013;Tan et al, 2016), Qinghai Lake (Hou et al, 2009;Jin et al, 2009;Xiao et al, 2012), Yamzhog Yumco Zhang et al, 2012;Sun et al, 2013;Zhe et al, 2017), Pumayum Co (Ju et al, 2010;Zhu et al, 2010), Nam Co (Gao et al, 2008;Wang et al, 2013), Mapam Yumco (Yao et al, 2015). Some scholars have also studied water chemistry in some areas of the QT (Zhang and Gustafsson, 1995;Guo and Wang, 2012;Tian et al, 2015), including microorganisms (Nie, 2011;Zhang et al, 2013;Zhao et al, 2017), heavy metals and trace elements (Cao et al, 2000;Grange et al, 2001;Li et al, 2006;Sheng et al, 2012;Tian et al, 2016).…”

What Caused the Decline of Water Level of Yamzho Yumco During 1975–2012 in the Southern Tibetan Plateau?

“…Thus, it is rich in hydropower resources. The YY pumped‐storage hydropower station was established in 1989 and has been operating since 1997 (Zhe et al, 2017) for providing power in the central Tibet, which had potential influence on the variability and changes of water budgets in the lake due to the water pump discharge. But unfortunately, there lacked observed data to quantify this effect.…”