Ionic sources and water quality assessment around a reservoir in Tehri, Uttarakhand, Garhwal Himalaya

The paper discusses the ionic sources and chemical quality of the waters (surface and groundwater) around the Tehri reservoir in Uttarakhand, Garhwal, Himalaya, for drinking and irrigation purposes. The main Bhagirathi river, tributary streams and springs and groundwater are the main sources of water for the reservoir and inhabitant living around it. Fifty-two water samples were collected from springs, handpumps (borewell) and streams and were analysed for major ions. The pH is varying from 6.8 to 8.6 and EC from 28 to 820 mu S/cm. The chemical composition of water is dominated by Ca, Mg and HCO3. The high ratio of Ca + Mg/Na + K and low ratio of Na + K/TZ indicate dominance of carbonate dissolution as the main solute acquisition process in this part of Lesser Himalaya. The trilinear and X-Y plots suggest less contribution from silicate weathering and anthropogenic activities. The excess of Na over Cl indicating much of the alkalis in the waters of Tehri area have source other than precipitation possibly from silicate weathering. Recharged by meteoric water, the quality of water in the study area is controlled essentially by chemical processes occurring between water and lithology and locally altered by human activities. Among the trace metals the concentration of Fe at few locations has marginally exceeded the WHO and BIS standards of drinking water. The analytical result computed from various water quality indices indicate fairly good quality of water for both drinking and irrigation purposes. The factor analysis performed on the major ion data indicate two factors are the most important affecting the water quality of the area.