Hydrochemical appraisal and solute acquisitions in Seti River Basin, Central Himalaya, Nepal

Ramesh Raj Pant; Faizan Ur Rehman Qaiser; Guanxing Wang; Subash Adhikari; Kiran Bishwakarma; Upendra Baral; Bhagawat Rimal; Youb Raj Bhatta; Kedar Rijal

doi:10.1007/s10661-021-09437-9

Hydrochemical appraisal and solute acquisitions in Seti River Basin, Central Himalaya, Nepal

Environ Monit Assess. 2021 Sep 17;193(10):656. doi: 10.1007/s10661-021-09437-9.

Authors

Affiliations

¹ Central Department of Environmental Science, Tribhuvan University, Kathmandu, Nepal.
² Department of Earth Sciences, COMSATS University Islamabad, Abbottabad Campus, Abbottabad, Pakistan.
³ Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China. wangguanxing@itpcas.ac.cn.
⁴ Provincial Policy and Planning Commission, Gandaki Province, Pokhara, Nepal.
⁵ Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.
⁶ University of Chinese Academy of Sciences, 100049, Beijing, China.
⁷ Kathmandu Center for Research and Education, CAS-TU, Kathmandu, Nepal.
⁸ Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China.
⁹ College of Applied Sciences (CAS)-Nepal, Tribhuvan University, Kathmandu, Nepal.

PMID: 34532822
DOI: 10.1007/s10661-021-09437-9

Abstract

The chemical characterization and assessment of the water quality in the headwater areas of the Himalaya are necessary for securing the water in the future. This study aims to assess the hydrochemistry and water quality concerning drinking and irrigational uses in the Seti River Basin (SRB), Nepal. A total of 45 water samples were collected in 2016 from the SRB during pre-monsoon, monsoon, and post-monsoon seasons, and pH, EC, TDS, and DO were measured on-site, whereas Ca²⁺, Mg²⁺, K⁺, Na⁺, Cl^-, SO₄^2-, NO₃^-, and dissolved Si were analyzed in the laboratory. The results revealed mildly alkaline pH (8.40 ± 0.43) with the pattern of average ionic dominancy: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and HCO₃^- > SO₄^2- > Cl^- > NO₃^- for cations and anions, respectively. Gibbs diagram implied that the lithogenic weathering mainly controlled the solute acquisition process, which was further confirmed by the Piper diagram, exhibiting Ca-HCO₃ as the governing hydrochemical facies (91%). The average molar ratios were 0.88, 8.33, and 6.86 of (Ca²⁺ + Mg²⁺)/TZ⁺, (Ca²⁺ + Mg²⁺)/(Na⁺ + K⁺), and HCO₃^-/(Na⁺ + K⁺), respectively, which specified that the carbonate weathering largely controlled the solute acquisition processes with a minor contribution of silicates. The mass budget calculation also confirmed the dominance of carbonate weathering (72.0%, 78.9%, and 62.0% in Pre-Monsoon, Monsoon, and Post-Monsoon, respectively) and the high monsoon rainfall's dilution effect to anthropogenic input of cations. Principal component analysis and correlation matrix exhibited that the major sources of ions in the basin were geogenic with minor anthropic signatures. Furthermore, water quality in connection to drinking and irrigation uses revealed that the basin has mostly retained its natural water quality. This investigation suggests that regular monitoring and assessment are essential for maintaining the water quality and ecological integrity in the Himalayan river basins.

Keywords: Major ions; Multivariate statistical techniques; Seti River Basin; Spatiotemporal variations; Water quality.

MeSH terms

Environmental Monitoring
Groundwater*
Nepal
Rivers
Water Pollutants, Chemical* / analysis
Water Quality

Substances

Water Pollutants, Chemical