Groundwater Quality Assessment using Geospatial Tools for Domestic and Irrigation Purposes for Lower Papagni River Basin in Chikkaballapura District, Karnataka, India

Abstract

Groundwater is the principal source of freshwater for domestic and agricultural needs in semi-arid regions of peninsular India. The present study evaluates the groundwater quality of the Lower Papagni River Basin in Chikkaballapura District, Karnataka, with special emphasis on its suitability for drinking and irrigation purposes. A total of 45 Post monsoon season groundwater samples were collected from bore wells (Fig. 2) and open wells and analyzed for major physico-chemical parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and anions (HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻, and F⁻) following standard laboratory procedures. Groundwater occurs mainly in weathered and fractured zones and is vulnerable to both geogenic and anthropogenic contamination. Fluoride enrichment, commonly associated with the dissolution of fluoride-bearing minerals in granitic terrains, has been widely reported in Karnataka. Field measurements of pH, Electrical Conductivity (EC), and Total Dissolved Solids (TDS) were recorded using portable meters, while major cations and anions were analyzed in the laboratory following standard procedures. The dominance of rock-weathering processes in the Gibbs diagram aligns with these elevated TDS values and indicates that the major ions originate from natural geogenic sources rather than anthropogenic pollution. Overall, the Gibbs plots confirm that groundwater chemistry is controlled primarily by geochemical weathering, and while most samples meet BIS and WHO permissible limits, a significant proportion exceeds desirable limits, requiring consideration for domestic suitability. A smaller portion, around 10–15%, plots toward the precipitation dominance zone, reflecting recharge from rainfall with comparatively low mineral content. Only about 2–5% of samples show trends toward the evaporation dominance zone, suggesting minimal influence of evaporative concentration in the region.