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Volcanic aquifers are vital groundwater resources in the Indonesian archipelago. This study investigates the southern slope of Mount Karang, a volcanic area with significant groundwater potential reflected in its abundant springs, to examine the influence of geological conditions on the physical and chemical characteristics of groundwater. The research combined geological mapping, observation of groundwater physical characteristics, and laboratory chemical analysis. Field observations identified 60 outcrops and 31 groundwater locations from springs and dug wells, with 12 samples collected for hydrochemical analysis. The results showed geological units comprising andesitic lava, lapilli tuff, volcanic breccia, and ash tuff, crossed by a northwest–southeast strike-slip fault zone. Based on lithology and fault patterns, groundwater was classified into six zones, with five facies identified: Ca-HCO₃, Ca.Mg-HCO₃, Na.K-Cl, Ca.Mg-SO₄, and Na.K-SO₄. Gibbs diagram and molar ratio analysis indicated mineral dissolution as the main factor controlling groundwater chemistry. Factor Analysis reduced nine groundwater characteristics into three principal components representing 86.54% of the variance, with Factor 1 dominated by calcium, potassium, pH, and total dissolved solids accounting for 51.42%. These findings demonstrate that geological factors significantly influence groundwater characteristics, providing important insights for the sustainable management of groundwater in volcanic areas.
Listiawan et al. (Thu,) studied this question.