The Himalayan ecosystem is one of the most fragile ecosystems in the world. Amid the growing changes in land use pattern due to deforestation, construction of multiple dams, mining, increased urbanization, and industrialization together with emission of green houses gases i.e CO2, NOx, CH4 and CFCs contributing to Global Warming has come to be seen as a risk affecting drastically the water chemistry of the region. The frequent cloud burst, avalanche, landslide along with flash flood are the most common human induced disaster which recurrently occurred in past few decades in the Himalayan region. This paper discusses about the impact of land use pattern on water chemistry of the region and spatial and temporal variation in water quality of the region.
Among anions, bicarbonate is most dominant anions which constitute around 60 % to 70 % anion followed by SO4 constituting around ~ 15% of anion. The high equivalent ratio of (Ca2+ + Mg2+)/ HCO3 ratio ~ (1.2) and relatively high contribution of (Ca+Mg) ) to total cations (TZ+) indicates carbonate weathering as the primary source of major ions. The carbonate weathering contributes around 80 % to 90 % of HCO3 while silicate contributes 5% -12 % HCO3 in the Himalayan catchment which implies the dominant of carbonate weathering. The ionic ratios and relative concentration of ions suggests that the major source of ions in water in the study areas remains rock weathering, although anthropogenic activities have influenced the ionic composition. Overall cation and anions concentration shows following trend in the study area HCO3>SO4>NO3>Ca>Cl>Mg>Na >Si > K >PO4>F. The surface water of study area belongs to Ca-Mg-HCO3 and Ca-Mg-SO4 Hydrochemical facies.