Assessment of Water Quality and Pollution Sources in Sabalan Dam Lake (Iran)

Sabalan Dam Lake, located at ~4,800 m above sea level in northwestern Iran, serves as a strategic freshwater source for Ardabil Province. Despite its high-altitude and volcanic setting, recent evidence suggests emerging water quality degradation due to a combination of geogenic and anthropogenic stressors. This study presents the first integrated assessment of pollution status, sources, and spatial distribution in the lake and its inflowing rivers during the spring season. Water samples from nine representative stations were analyzed for physicochemical, microbiological, and heavy metal parameters (Pb, Cd, Zn, Cu), and results were evaluated against WHO, EPA, and Iranian national standards. GIS-based spatial interpolation was employed to identify pollution hotspots and link them to potential sources. Findings revealed that while most physicochemical parameters remained within permissible limits, lead (28.85–62.72 µg/L) and cadmium (11–23.94 µg/L) concentrations exceeded WHO and EPA thresholds by 2–8 times across all stations attributed to natural leaching from Sabalan’s andesitic-basaltic formations and anthropogenic inputs from upstream rural settlements. Microbiological contamination was widespread, with total coliforms (260–1,100 MPN/100mL) and fecal coliforms (0–1,150 MPN/100mL) indicating significant fecal intrusion, particularly near villages and livestock areas. The lake has shifted from an oligotrophic to a mesotrophic state (mean TP ≈ 20 µg/L), signaling early eutrophication. Spatial analysis identified three critical hotspots (Stations 2, 6, and 8) where geogenic metal release and rural pollution converge. These results challenge the assumption that high-altitude lakes are inherently pristine and underscore the dual vulnerability of volcanic reservoirs to natural and human-induced pressures. We recommend a dual-track management strategy: (1) geochemical mitigation (e.g., lime softening to reduce metal bioavailability) and (2) source control (e.g., decentralized wastewater systems, livestock exclusion zones). This study provides a replicable framework for assessing data-scarce, high-elevation reservoirs in arid and semi-arid regions globally.