Hydrogeochemical characteristics and water quality assessment of the Tara River Basin, Montenegro

Study region The Tara River Basin, Montenegro, is a UNESCO-protected mountain karst system of high ecological and socio-economic value, increasingly affected by tourism, irrigation development, infrastructure expansion, and potential mining activities. Study focus This study presents the first integrated hydrogeochemical assessment of the basin based on a multi-year monitoring dataset (2018–2023). Hydrochemical indicators, source-rock deduction techniques, hierarchical cluster analysis (HCA), and principal component analysis (PCA) were applied to identify dominant hydrogeochemical processes, assess ecological status, and evaluate irrigation suitability. New hydrological insights for the region Water chemistry is primarily controlled by carbonate dissolution, producing Ca–HCO₃ and Ca–Mg–HCO₃ water types, with a secondary influence of silicate weathering. The Ca²⁺/Mg²⁺ ratio (>2) indicates calcite dominance, whereas lower values occur during low-flow conditions. HCA identified two main groups reflecting hydrological regime and variable contributions of lithology and anthropogenic inputs. PCA (71.9%) revealed four dominant processes: calcite dissolution; combined effects of silicate weathering, marine aerosols, and anthropogenic inputs; groundwater contributions associated with faecal contamination; and nitrate-related redox processes. Overall, water quality is high, with most parameters indicating good ecological status; however, an isolated Hg exceedance requires verification. Irrigation suitability remains favourable (C1–C2, S1), highlighting both the agricultural potential of the basin and the importance of continued long-term monitoring in sensitive mountain karst environments.