Evaluating Karst aquifer dynamics through integrated geomorphological and geo-hydro-chemical approaches: Insights from the Central Zagros Mountains, Iran

Abstract

Karst aquifers in semi-arid regions are highly vulnerable to climatic variability and groundwater overexploitation due to limited recharge, strong water–rock interactions, and structurally controlled flow paths. The Pirghar and Dimeh karst catchments in the Central Zagros Mountains of Iran represent two contrasting hydrogeological systems that supply critical freshwater resources under semi-arid conditions. This study applies an integrated geomorphological, hydrochemical, and hydrodynamic framework to evaluate karstification intensity, aquifer behavior, and groundwater quality in these basins. Geochemical analyses (XRD, XRF, and calcimetry), hydrochemical characterization, spring hydrograph recession analysis, Gibbs diagrams, and fuzzy logic-based sinkhole susceptibility mapping were combined to assess aquifer structure and dominant geochemical processes. Recession analysis indicates a well-developed conduit-dominated system in the Pirghar aquifer (recession coefficients: 0.008–0.014 day⁻¹), whereas the Dimeh aquifer exhibits more diffuse and restricted flow conditions (0.004–0.006 day⁻¹), reflecting contrasting recharge and storage dynamics typical of semi-arid karst systems. Groundwater in both catchments is predominantly of the Ca–HCO₃ type, with calcite and dolomite dissolution as the primary sources of dissolved ions. Seasonal variations in Mg²⁺/Ca²⁺ ratios (Pirghar: 0.27–0.45; Dimeh: 0.18–0.32) highlight differences in groundwater residence time and aquifer maturity under limited recharge conditions. Gibbs diagrams confirm that water–rock interaction is the dominant control on groundwater chemistry, with minimal influence from evaporation. Sinkhole development is concentrated in highly karstified zones associated with steep slopes, higher elevations, and proximity to major faults. Water quality assessment shows that 85% of samples are suitable for drinking and 72% for irrigation. The results provide insight into the functioning of karst aquifers in semi-arid environments and offer a transferable framework for identifying vulnerable recharge zones, improving groundwater management, and mitigating sinkhole hazards in data-scarce arid and semi-arid regions.