Karst landscapes, covering approximately 15.2% of the global land surface, are dominantly shaped by carbonate dissolution processes such as infiltration, dissolution, and precipitation. These terrains host some of the most complex and heterogeneous groundwater flow systems, thereby warranting a detailed investigation. Geochemical evolution of groundwater in these aquifers is determined by the original composition of recharge water, physicochemical characteristics of the geological strata through which the water flows, and rock-water interactions along its flow path. This study has been carried out to investigate these processes operating within the karst region surrounding the Belum Cave, within the Narji limestone formation of the Kurnool subgroup, Andhra Pradesh, India. It explores the impact of lithology, climate change, and anthropogenic and agricultural activities on the groundwater hydrochemistry and its suitability for drinking purposes. Water samples were collected during both pre-monsoon (PRM) and post-monsoon (POM) seasons from dug wells, bore wells, springs, a reservoir, and a quarry. These samples were analysed for key physico-chemical parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Calcium (Ca+ 2), Magnesium (Mg+ 2), Sodium (Na+), Potassium (K+), Alkalinity (HCO3−), Chloride (Cl−), Nitrate (NO3−), Sulfate (SO42−), and Fluoride (F−). Spatial and temporal variations in major ion concentrations suggest that groundwater is alkaline and moderately enriched with salts, indicating fluctuations in runoff and infiltration patterns that influence its geochemistry. Multivariate statistical analysis, such as, Pearson’s Correlation and Principal Component Analysis, were applied to identify correlations and groupings amongst chemical parameters. The hydrogeochemical characteristics reveal a complex interplay between natural and anthropogenic factors. Seasonal variations significantly influence groundwater composition through differences in recharge, evaporation, and dilution effects. The predominance of Ca2+, Mg2+, and HCO3− indicates carbonate dissolution (Calcite and Dolomite) plays a significant role in shaping groundwater chemistry. Gibb’s diagram for both seasons indicates rock-water interaction as primary process controlling the water chemistry. The Piper trilinear plot reveals that the groundwater is primarily of the Ca-Mg-HCO3 type, with a shift towards Ca-Mg-Cl-SO4 facies at certain locations, likely due to agricultural inputs. Reverse ion exchange processes appears to play a key role in regulating the groundwater composition. Saturation indices of various mineral phases suggests supersaturation of carbonate minerals and undersaturation of halite, reflecting ongoing geochemical reactions and the dynamic equilibrium status of the aquifer system. The Water Quality Index (WQI) placed majority of samples in the poor to very poor class for direct consumption; however, appropriate treatment could render them suitable for drinking. Variations in rainfall significantly affect geochemical signatures by influencing dissolution and dilution processes within the karst aquifer. Overall, the study reveals the importance of monitoring groundwater in karst systems, where lithology, climatic variability, and anthropogenic and agricultural activities collectively control water chemistry and its long-term suitability for human use.

Geochemical controls on groundwater quality in a Karst Aquifer system: a case study from the Belum Cave Region, Andhra Pradesh, South India

期刊论文
发表日期：

2026年5月12日

查看全文

Vivek K. Bhore,
Satyajit K. Gaikwad,
Satish Sangode,
Dhananjay Meshram,
Aniket Muley,
Shubham Waghmare,
Mahesh Mopkar

摘要

Karst landscapes, covering approximately 15.2% of the global land surface, are dominantly shaped by carbonate dissolution processes such as infiltration, dissolution, and precipitation. These terrains host some of the most complex and heterogeneous groundwater flow systems, thereby warranting a detailed investigation. Geochemical evolution of groundwater in these aquifers is determined by the original composition of recharge water, physicochemical characteristics of the geological strata through which the water flows, and rock-water interactions along its flow path. This study has been carried out to investigate these processes operating within the karst region surrounding the Belum Cave, within the Narji limestone formation of the Kurnool subgroup, Andhra Pradesh, India. It explores the impact of lithology, climate change, and anthropogenic and agricultural activities on the groundwater hydrochemistry and its suitability for drinking purposes. Water samples were collected during both pre-monsoon (PRM) and post-monsoon (POM) seasons from dug wells, bore wells, springs, a reservoir, and a quarry. These samples were analysed for key physico-chemical parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Calcium (Ca^+ 2), Magnesium (Mg^+ 2), Sodium (Na⁺), Potassium (K⁺), Alkalinity (HCO₃⁻), Chloride (Cl⁻), Nitrate (NO₃⁻), Sulfate (SO₄²⁻), and Fluoride (F⁻). Spatial and temporal variations in major ion concentrations suggest that groundwater is alkaline and moderately enriched with salts, indicating fluctuations in runoff and infiltration patterns that influence its geochemistry. Multivariate statistical analysis, such as, Pearson’s Correlation and Principal Component Analysis, were applied to identify correlations and groupings amongst chemical parameters. The hydrogeochemical characteristics reveal a complex interplay between natural and anthropogenic factors. Seasonal variations significantly influence groundwater composition through differences in recharge, evaporation, and dilution effects. The predominance of Ca²⁺, Mg²⁺, and HCO₃⁻ indicates carbonate dissolution (Calcite and Dolomite) plays a significant role in shaping groundwater chemistry. Gibb’s diagram for both seasons indicates rock-water interaction as primary process controlling the water chemistry. The Piper trilinear plot reveals that the groundwater is primarily of the Ca-Mg-HCO3 type, with a shift towards Ca-Mg-Cl-SO4 facies at certain locations, likely due to agricultural inputs. Reverse ion exchange processes appears to play a key role in regulating the groundwater composition. Saturation indices of various mineral phases suggests supersaturation of carbonate minerals and undersaturation of halite, reflecting ongoing geochemical reactions and the dynamic equilibrium status of the aquifer system. The Water Quality Index (WQI) placed majority of samples in the poor to very poor class for direct consumption; however, appropriate treatment could render them suitable for drinking. Variations in rainfall significantly affect geochemical signatures by influencing dissolution and dilution processes within the karst aquifer. Overall, the study reveals the importance of monitoring groundwater in karst systems, where lithology, climatic variability, and anthropogenic and agricultural activities collectively control water chemistry and its long-term suitability for human use.