Findings on water quality in Upper Mustang (Nepal) from a preliminary geochemical and geological survey

Abstract

The major ion and trace element chemistry of water samples, including springs, rivers and irrigation ditches, collected during a survey on August 2016 in the Upper Mustang region of the Mustang District of Dhawalagiri Zone (Nepal) has been investigated. The Upper Mustang region, a cold desert, represents a hot-spot for climate change: indeed, violent hailstorms and rainstorms have been recently observed, consequently exposing land to erosion. Results of this study indicate that waters in the region belong to the Caâ\u80\u93HCO3, Caâ\u80\u93Mgâ\u80\u93Clâ\u80\u93SO4and Naâ\u80\u93Kâ\u80\u93Cl-types, reflecting different hydrochemical regimes. Uranium is widespread in waters, with concentrations up to 19 µg/L recorded in a potable water supply. Locally, anoxic conditions affect uranium mobility due to the low solubility of U(IV) minerals. Highly toxic thallium was detected in a thermal spring at an elevated concentration (45 µg/L Tl). The association of thallium with high concentrations of iron suggests that these elements are derived from pyrite oxidation. Detectable levels of thallium were also measured in the water of an irrigation ditch. Lithium concentrations ranged from 7 µg/L to 12 mg/L in the thermal water and showed a strong association with chloride ions. Arsenic concentrations up to 4.7 µg/L were measured in tributaries of the Kali Gandaki river. The data provide evidence that solutes in water have originated from an array of input sources, including carbonate dissolution, the dissolution of soluble salts, silicate weathering and localized sulfide oxidation. In particular, chemical weathering of granitic rocks is likely the primary source for metals and metalloids in waters. Since the erosion rate is a factor affecting lithological weathering, high-intensity rainfalls due to climate change are expected to influence the release and fate of potentially harmful elements in the in the Upper Mustang Valley

Patterns of livestock depredation by snow leopards and effects of intervention strategies: lessons from the Nepalese Himalaya

“…Located in the rain shadow of the Annapurna Range, this area receives less than 300 mm of annual precipitation in Upper Mustang and about 600 mm in Manang (Department of Hydrology and Meteorology 2017). The Upper Mustang region is covered mainly by cold deserts deprived of forest (Chetri et al 2017;Ghezzi et al 2017) and is characterised by an arid cold steppe climate with strong winds (Karki et al 2015). In contrast, the Manang region has polar and cold climates (Aryal et al 2014b;Karki et al 2015) and is covered by forest comprised of the Himalayan white pine (Pinus wallichiana), East Himalayan fir (Abies spectabilis), Himalayan birch (Betula utilis) and black juniper (Juniperus indica; Ghimire and Lekhak 2007).…”

Headwater Flow Geochemistry of Mount Everest (Upper Dudh Koshi River, Nepal)

“…On the other hand, Al, Ti, Fe, and Mn to a lesser extent increase in all the sites during the monsoon season. In comparison with the Upper Mustang rivers in the western region of Nepal Himalaya (Ghezzi et al, 2017), the concentrations are elevated, from 5 to 6600 µg/L for Al, from 0.5 to 485 µg/L for Ti, from 5 to 7130 µg/L for Fe, and from 2 to 200 µg/L for Mn. These elements are mobilized by the surface runoff during the monsoon season and their common origin is to be found in the weathered bedrock.…”

“…During the past decade, geochemistry studies have been conducted of the Himalaya water flows (e.g., Jeelani et al, 2011;Ghezzi et al, 2017), but no study has been undertaken in the context of very high altitudes covering dynamically an entire year. This issue underlines the exploratory character of the current study, which, however, does not aim to address all the questions raised in this exceptional framework.…”

Hydrochemical and quality assessment of irrigation water at the trans-himalayan high-altitude regions of Leh, Ladakh, India

“…SiO 2 /(Na + K-Cl), (Na + K-Cl)/ (Na + K-Cl + Ca), Ca/(Ca + SO 4 ), TDS, and Cl − /sum anions, and different types of weathering processes like cation exchange, plagioclase weathering unlikely, calcium source other than gypsum-carbonate or silicates, silicate weathering, and rock weathering are found, respectively (Table 7). The presence of different types of weathering processes at such a high-altitude region might be due to a change in the global climate pattern in this scenario of global warming, which leads to a change in the hydro-geochemical process (Quade et al 2001(Quade et al , 2003Ghezzi et al 2017;Singh et al 2017;Pant et al 2018;Sabin et al 2020).…”

“…Environmental change has impacted social life, the pattern of the agro-animal cluster, the weathering cycle, and the groundwater and surface water quality (New 2009;Bharti et al 2017a;Ghezzi et al 2017;Singh et al 2017;Pant et al 2018;Giri 2019;Murali et al 2020;Giri et al 2020). Highaltitude areas are more vulnerable to food security since 12% of the global human population suffers from the impact of global warming (Skoet et al 2006;Lamprecht et al 2018;Convey and Peck 2019).…”