Abstract
Vertical electrical sounding (VES), geological, and hydrochemical data were integrated to assess aquifer characteristics and pollution risks in Kulon Progo. The VES data come from 13 stations surveyed with the Schlumberger configuration, selected for its ability to explore deeper subsurface environments with cost-effective electrode spacing. The VES data were inverted with PROGRESS 3.0, a 1D layered resistivity modeling software capable of producing numerical and graphical results. All hydrochemical parameters (total dissolved solids (TDS), pH, NO 3 , NO 2 , Cr 6+ , Fe, Mn) were within acceptable standards except for one well with turbidity (36.6 NTU) and Fe (0.5261 mg/L) far beyond the standards. According to the Regulation of the Republic of Indonesia Minister of Health No. 32/2017, acceptable values were 5 NTU for turbidity and 0.3 mg/L, for Fe. High levels of microbiological contamination, indicated by the presence of Escherichia coli (E. coli) and coliform bacteria far in excess of 0 CFU/100 mL, were also detected. Strong negative correlations ( r < –0.7) between resistivity and microbially/metal-associated parameters like TDS ( r = –0.732) suggest that low-resistivity, clay-rich areas are more susceptible to contamination. Overall, the study revealed that although groundwater in the area is of chemical quality, its microbiological quality poses severe health risks, thus an urgent need for proper treatment and enhanced groundwater management practices.