TITLE:
Factor Analysis of Seasonal Hydrochemical Data of the Varthur Catchment Area, Bangalore Urban District, Karnataka
AUTHORS:
L. Muni Krishna, H. C. Vajrappa
KEYWORDS:
Groundwater Quality, R-Mode Factor Analysis, Principal Component Analysis, Hydrochemistry, Seasonal Variation, Anthropogenic Contamination, Varimax Rotation, Spatial Factor-Score Mapping
JOURNAL NAME:
Open Journal of Geology,
Vol.16 No.7,
July
10,
2026
ABSTRACT: Seasonal groundwater-quality variability across the Varthur Catchment, Bangalore Urban District, was assessed using R-mode factor analysis applied independently to pre- and post-monsoon 2023 hydro chemical data from 58 bore wells. The correlation matrix showed strong positive associations among EC, TDS, TH, Ca, Mg, Na, Cl and SO4 in both seasons, indicating that mineral dissolution and rock-water interaction govern groundwater mineralization. Four and three factors were retained for the pre- and post-monsoon datasets, explaining 77.22% and 72.70% of total variance, respectively. In both seasons, Factor I loaded heavily on Ca, Mg, Cl, SO4, EC, TH and TDS and is interpreted as a hardness-mineralization factor reflecting geogenic rock-water interaction. Factor II reflected alkali enrichment and ion exchange, dominated by K pre-monsoon and by pH post-monsoon, while a distinct carbonate/bicarbonate factor emerged in both seasons. A separate nitrate-dominated factor (loading 0.972) was retained pre-monsoon, indicating concentrated anthropogenic contamination during the dry season; post-monsoon nitrate loadings were weak and diffuse, consistent with dilution by monsoon recharge. Spatial mapping of factor scores showed that hardness-mineralization zones coincide with deeper water tables and dense urban development in the south-central and northern catchment, whereas nitrate hotspots persist near dense settlement and residual agriculture in the north. Overall, Varthur groundwater chemistry is governed by lithogenic weathering and carbonate equilibrium, with a superimposed, seasonally modulated anthropogenic nitrate signal.