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⁻ > SO₄²⁻ > 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.

喜马拉雅上游源区水质的化学表征和评估对于确保未来的水源是必要的。本研究旨在评估尼泊尔塞蒂河流域 (SRB) 与饮用水和灌溉用途有关的水化学和水质。2016 年在季风前、季风和季风后季节从 SRB 共采集了 45 个水样，现场测量了 pH、EC、TDS 和 DO，而 Ca ²⁺、Mg ²⁺、 ķ ⁺，钠⁺，氯^˗，SO ₄ ^2˗，NO ₃ ^˗和溶解的硅在实验室中进行了分析。结果显示弱碱性 pH (8.40 ± 0.43) 具有平均离子优势模式：Ca ²⁺ > Mg ²⁺ > Na ⁺ > K ⁺和 HCO ₃ ⁻  > SO ₄ ²⁻  > Cl ^˗  > NO ₃ ^˗阳离子和阴离子，分别。Gibbs 图暗示成岩风化主要控制溶质获取过程，Piper 图进一步证实了这一点，显示 Ca-HCO ₃作为控制水化学相（91%）。(Ca ²⁺  + Mg ²⁺)/TZ ⁺、(Ca ²⁺  + Mg ²⁺ )/(Na ⁺  + K ⁺ ) 和 HCO ₃ ^- /(Na ⁺  + K ⁺)，分别说明碳酸盐风化在很大程度上控制了溶质获取过程，而硅酸盐的贡献很小。质量预算计算还证实了碳酸盐风化的主导地位（季风前、季风和季风后分别为 72.0%、78.9% 和 62.0%）和季风降雨对人为阳离子输入的稀释效应。主成分分析和相关矩阵表明，盆地中离子的主要来源是地质成因，人为特征较小。此外，与饮用和灌溉用途相关的水质表明，该流域大部分保留了其天然水质。