This dataset contains concentrations of fluoride, chloride, sulfate, nitrate, sodium, magnesium, potassium, silicon, calcium, aluminium, manganese, and iron from stream-water samples collected along the first 3.25 km of the Wiesent karst headwater stream in northern Bavaria, Germany, from March 2023 to May 2024. The dataset supports analyses of hydrochemical variability under varying hydroclimatic conditions.