The data set contains δ2H and δ18O from fortnightly grab samples in streamflow and corresponding monthly precipitation derived from interpolation for 23 Swiss hydrological catchments. δ2H and δ18O in streamflow are provided as one ASCII file for each station. Additionally to these time series each of the files contains the Deuterium excess, the streamflow conditions preceding the sampling as well as the z-scores indicating if a sample might be a statistical outlier, assuming the data are normally distributed. All files contain further information for each sample whether double measurement was performed in the lab comments indicating for instance special sampling conditions or storage-related issues that could alter the isotopic composition due to fractionation. For each data file for streamflow data there is a corresponding ASCII file for catchment precipitation. These contain the interpolated δ2H and δ18O in precipitation for the catchment as well as the source data that were used to derive the interpolated values. Associated data that can be useful for applications are provided. This is mean areal precipitation and temperature (ASCII files) as well as the topographic catchment boundaries (shape files).

The basic data for the interpolation of isotopic compositions in precipitation came from NISOT provided by FOEN, the National Groundwater Monitoring, NAQUA, from GNIP provided by IAEA as well as ANIP from the Environment Agency Austria. The areal precipitation and temperature were caclulated based or the gridded data products "Rhires" and "Tabs" provided by MeteoSwiss.