[en] In the glacierized catchment area of the Rofenache (Oetztal Alps, Austria) during several years measurements have been made of the environmental isotopes ²H, ¹⁸O and ³H in the precipitation, in snow and ice samples and in the runoff. Furthermore the electrolytic conductivity of runoff samples was measured and tracing experiments were made with fluorescent dyes. From core samples drilled in the accumulation area of the Vernagtferner, the gross beta activity was investigated and compared with both, the data from ²H, ³H und ¹⁸O analyses and the data from mass balance studies. It is shown that the annual net balance from previous years can be recovered on temperate glaciers using environmental isotope techniques. From the diurnal variations of the ²H and ³H contents and the electrolytic conductivity the following proportions in the runoff of the Vernagtferner catchment area were obtained during a 24-hour interval at a time of strong ablation (August 1976): about 50% of ice melt water, 25% of direct runoff fo firn- and snow melt water, and 7% of mineralized groundwater. The rest of the runoff consists of not mineralized melt water seeping from the glacier body. The annual variations of the ²H and ³H contents in the runoff of the glacierized catchment area permit conclusions on the time sequence of the individual ablation periods and on the residence time on the basis of model concepts. The residence times of approximately 100 days or 4 years, respectively, are obtained from the decrease in the ²H content at the end of the ablation period and from the variation of the ³H content in the winter discharge. (orig.)