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Global analysis of streamflow regimes is a neglected aspect of comparative hydrology. The regionalization of river regimes provides a useful tool for extrapolation of hydrological variables and for the identification of natural flow regimes where intensive river regulation has occurred. Previous studies at the global scale have used climatic characteristics to define regime types and the boundaries of climatic zones for extrapolation. These procedures have been made necessary by the lack of a suitable data set of stream flows with a global coverage. Such a data set has now been assembled for the first time and is used here to produce a classification of seasonal flow regimes based on a cluster analysis of the monthly mean flows expressed as percentages of the mean annual flow. Clustering was carried out using the within-group average method with cosine similarity measure after removing streams with no significant …