Abstract

Groundwater in the hills and mountains is manifested as springs, the major water sources for people in Nepal's mountainous regions. The aim of this study was to investigate seasonal variations of in-situ groundwater physicochemical parameters, evaluate groundwater hydrochemistry with respect to water types, and identify groundwater chemistry control mechanisms by analyzing spring water. The area's geology is dominated by schist and gneiss. Depression and fracture springs occur widely. The study involved observation of seasonal variations in in-situ physicochemical parameters pH, EC, TDS, DO, and temperature, and major ion concentrations – Ca2+, Mg2+, Na+, K+, HCO3, Cl, SO42− – to describe the water's chemical characteristics. The seasonal variations in physicochemical parameters arose mainly from monsoonal precipitation and its interactions with host rocks. Chemical analysis showed that Ca-HCO3 type water dominated indicating shallow aquifer groundwater processes. The relative abundance of cations was, in order, Ca2+ > Na+ > Mg2+ > K+ and of anions HCO3 > Cl > SO42−. Lithological contributions from the interactions of rocks with water across spring flow networks were the major mechanisms controlling spring water chemistry.

Highlights

  • Springs are major sources of drinking water mainly in rural and semi-urban areas as well as in the surroundings of urban areas in the middle hill region of Nepal. Spring water quality dynamics in different seasons also affects human health. Therefore, spring water quality and seasonal variations of spring water quality becomes very important to assess for increasing water security of rural populations in Nepal. Moreover, springs are also major sources of non-snowfed rivers during lean season

  • maintaining base flows. Thus, it is very important to understand how spring discharge variation happening in a watershed.

  • This manuscript investigates the spring discharge, quality of spring water in the Indrawati River, a major tributary of the Melamchi River, depending which a major drinking water supply project to Kathmandu Valley is almost completed.

  • The insitu physicochemical water quality parameters along with major cations and anions are determined with spring discharge of the area providing new insights how water and rock interactions generate ultimate water quality of spring water is highlighted.

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