University of Petroleum & Energy Studies,Dehradun, India.

 Wadia Institute of Himalayan Geology, Dehradun India.

Major ion chemistry of Asan river catchment were studied to find the out the impact of anthropogenic activities on water quality. Surface and groundwater samples were collected from Asan Catchment, surface water samples were collected from Asan river while ground water samples were collected from tube wells and hand pumps. The parameters i.e. pH , EC, TDS, SO^2-₄, Cl^-,  NO^-₃, PO^2-₄SO₄, HCO^-₃, total hardness, Ca²⁺, Mg²⁺, Na⁺, K⁺  were analyzed  for  studying  major ion chemistry of  surface and groundwater of Asan river catchment. Total 38 samples were collected from surface and subsurface water. The physical parameter like temperature, conductivity and pH, DO were measured in the field while for the analysis of remaining parameters, samples were brought in laboratory and analyzed by using standard methods of APHA for water and waste water analysis. Ion- chromatography were used for the analysis of cations (Ca²⁺, Mg ²⁺, Na ⁺, K⁺) and anions (SO^2-₄, Cl^-,  NO^-₃, PO^2-₄, F^-).The ions i.eCa, Na, and HCO₃ were found to be dominant ions in surface and groundwater. The average (Ca+Mg): HCO₃ equivalent ratio of 1.4, relatively high contribution of (Ca+Mg) to the total cations (TZ+) and high (Ca+Mg): (Na+K) equivalent ratio of 9.1 indicate that carbonate weathering is the primary source of major ions to these water. Study result shows that water is slightly acidic to basic in nature. The EC were ranged from 54.2 to 1353 micro Siemens/, TDS ranged from 91 mg/l to 553 mg/l, HCO₃ were ranged from 21.0 mg/l to 366 mg/l and pH were ranged from 6.0 to 8.7. All cations and anions were compared with WHO and BIS Standard of drinking water quality in order to ascertain its suitability for drinking purpose.

Keywords: Asan Catchment; Ion chemistry; Water quality.