Catchment Controls of the Hydrochemistry of High-Altitude Lakes in the High Tatra Mountains (Slovakia)

Catchment characteristics significantly influence water composition in pristine mountain lakes, receiving similar atmospheric deposition. We analysed these relationships for 20 subalpine and alpine catchment–lake systems in the High Tatra Mountains (Slovakia), using a comprehensive new dataset of detailed catchment characteristics and mean water chemistry from 2021 to 2024. Redundancy analysis indicated that catchment characteristics explained 47% of the spatial variability in lake hydrochemistry. The most influential parameters were land cover (20%), terrain slope (11%), lake-to-catchment area ratio (8%), and bedrock geology (8%). Cation concentrations were dominated by Ca2+, while anions were dominated by HCO3−. Concentrations of Na+, K+, Cl−, dissolved organic carbon (DOC), and total organic nitrogen (TON) were higher, while NO3− was lower, in lakes with greater soil and vegetation cover in catchments. Concentrations of Na+, K+, Mg2+, Ca2+, HCO3−, Cl−, SO42−, silicon (Si), and DOC decreased with increasing altitude, whereas Na+, K+, SO42−, NO3−, NH4+, and Si increased with catchment slope. Catchment bedrock geology affected K+, SO42−, and Si concentrations in lake water. More than 50% of the observed variability remained unexplained, indicating that additional climatic and hydrological drivers may influence lake hydrochemistry and represent important directions for future research.