Evaluation of hydrogeochemical controlling factors and water quality index of water resources of the Barak valley of Assam, Northeast India

The hydrogeochemical processes and water quality index of Barak Valley of NE India has carried out to delineate the processes controlling the quality. 33 water samples representing river, pond, lake, paleochannel, groundwater were selected. Analyses using correlation matrix, scatter plots, Schoeller, Gibbs, Trilinear, Ternary diagrams and water quality index were examined. The water type is characterized by high HCO3 (70% in SW and 66% in GW) and depleted SO4 (< 0.5% of TDS) indicating significant bacterial reaction. Gibbs diagram, bivariate relations of Na/Cl, Ca/Mg vs. Na/Cl, Ca+Mg vs. TZ suggest silicate weathering. The scatter plots of Ca +Mg vs. HCO3+SO4, Ca/Mg vs. Na/Cl, (Ca+Mg)/(HCO3+SO4), (Na-Cl) vs. (Ca+Mg-HCO3+SO4) further indicate normal ion exchange. Chemically the surface water evolved through initial stage depicting Ca-Mg-HCO3 type while groundwater represents mixed type. WQI suggest not suitable for drinking due to excessive elevation of As, Fe, Mn. However, SAR, %Na recommend for drinking and agricultural uses.