Hydro-geochemistry of the Bindal River Catchment: water suitability for irrigation and drinking in the Doon Valley outer Himalaya

Abstract

ABSTRACT The hydrogeochemical analysis of surface water and groundwater in the Bindal river catchment was conducted in the Doon Valley of Uttarakhand, situated in the Outer Himalayan region. The surface and ground water samples were collected from 13 sampling stations located at the Bindal river catchment. The pH ranged from 6.93 to 7.62, with an average value of 7.23, signifying a slightly alkaline nature. The electric conductivity concentration varied from 655 µs/cm to 1309 µs/cm, with a mean value of 865.54 µs/cm. The equivalent ratio of Ca2+ + Mg2+ (µEq/l vs total cation (TZ+) was varied from 1.05 to 10.7 with a mean value of 1 and the equivalent ratio of Ca2+/Mg2+ was 1.04 and the ratio of Ca2+ + Mg2+ (µEq/l) vs Na + K (µEq/l) was 10 indicating the dominance of carbonate weathering. As per Piper diagram, the dominance of weak acids (HCO3 −) over strong acids (SO4 2-, Cl−) was observed and majority of samples were alkaline earth and the alkaline earths (Ca2+ + Mg2+) were dominant over alkalis (Na+ + K+). The scatter plot Ca2+ + Mg2+ (µeq/l) and HCO3 − showed that few of the points fell along the 1:1 equiline, indicating that Ca2+ + Mg2+ in most of the sampling locations were almost balanced by HCO3 −. However, few points also fall away from 1:1 equiline indicating Ca2+ + Mg2+ are to balances by other ions, possibly sulphate ions, which were the second-largest ions in the study area. Two principal components were selected in this region and their eigenvalues were >1 and accounted 73% of cumulative variability in the data. The aptness of water for irrigation purposes was calculated via SAR value, Kelly’s Index, Wilcox, residual sodium carbonate, Na%, etc. The Piper plot indicated carbonate weathering is the dominant source of ions in the water, attributed to the prevalence of high-concentration dolomite and calcite rocks in the study area. Total order of ions follows HCO3 − > Ca2+ > Mg2+ > SO4 2- > Cl− > Na+ > NO3 − > K+ > PO4 3- > F− order. Apart from TDS, Ca2+, SO4 2- and K+, all the other parameters were within the acceptable limits as per Bureau of Indian Standards (BIS) for drinking water quality.