This dataset contains location information, field-measured hydrological and in-situ hydrochemical parameters from stream water samples collected at 13 sampling sites along the first 3.25 km of the Wiesent karst headwater stream in northern Bavaria, Germany, from March 2023 to May 2024. Parameters include latitude, longitude, elevation, distance to the spring, stream width and depth, discharge, water temperature, pH, electrical conductivity, redox potential, and dissolved oxygen.