<p>The Himalayan rivers are highly susceptible to climate change and human activities, impacting vital water sources for drinking, domestic use, irrigation, hydropower, and industry in both upstream and densely populated downstream areas. This study examines the complex relationship between hydrochemical characteristics and water quality in the Badigad River Basin (BRB), Lesser Himalayas, Nepal. To evaluate the water quality and chemical characteristics, 50 surface water samples were collected from tributaries and the main river and thoroughly analyzed by using hydrochemical indices, and multivariate analysis. Onsite measurement was conducted for pH, electrical conductivity, total dissolved solids followed by laboratory analyses to determine major ions, F-CO₂, total hardness, and calcium hardness. The results indicated slightly alkaline water with an average pH of 7.73 and Ca²⁺ was the dominant cation, followed by Mg²⁺, Na⁺, K⁺, and NH₄⁺. Among anions, HCO₃⁻ was predominant, followed by SO₄²⁻, Cl⁻, NO₃⁻, and PO₄³⁻. PCA identified four key factors governing water chemistry in the BRB, reflecting distinct sources such as carbonate weathering and anthropogenic inputs. HCA revealed marked spatial heterogeneity in water quality, underscoring the need for site-specific management approaches that integrate geological settings, land use patterns, and socio-cultural priorities. Gibbs plot emphasized the major role of rock weathering, while Piper and mixing plots indicated prevalent carbonate weathering. The water quality index and irrigation indices confirmed the suitability of surface water for drinking, domestic, and irrigation purposes. This study underscores the importance of understanding water quality dynamics and chemical characterization in the context of global climate change, providing valuable insights for decision-makers and stakeholders in the sustainable management of the ecologically sensitive Himalayan River Basins.</p>