In regions with no discharge measurements, one must rely on estimating flow characteristics. The discharge regimes which appear on the map provide the basis for estimating long-term average monthly flows. The long-term average seasonal variations of runoff will be referred to in this work as "regime" in accordance with the classical use of the term.
For the purposes of classification and regionalisation of the regimes, approximately one hundred catchments were selected from the hydrological network of the federal government, the cantons and private institutions. These catchments are between 10 and 500 km² in area, have natural discharge not influenced by the presence of large lakes, and have homogeneous, long-term measurement series.