Temporary streams are those water courses that undergo the recurrent cessation of flow or the complete dry-ing of their channel. The structure and composition of biolog-ical communities in temporary stream reaches are strongly dependent on the temporal changes of the aquatic habitats determined by the hydrological conditions. Therefore, the structural and functional characteristics of aquatic fauna to assess the ecological quality of a temporary stream reach cannot be used without taking into account the controls im-posed by the hydrological regime. This paper develops meth-ods for analysing temporary streams' aquatic regimes, based on the definition of six aquatic states that summarize the transient sets of mesohabitats occurring on a given reach at a particular moment, depending on the hydrological condi-tions: Hyperrheic, Eurheic, Oligorheic, Arheic, Hyporheic and Edaphic. When the hydrological conditions lead to a change in the aquatic state, the structure and composition of the aquatic community changes according to the new set of available habitats. We used the water discharge records from gauging stations or simulations with rainfall-runoff models to infer the temporal patterns of occurrence of these states in the Aquatic States Frequency Graph we developed. The visual analysis of this graph is complemented by the devel-opment of two metrics which describe the permanence of flow and the seasonal predictability of zero flow periods. Fi-nally, a classification of temporary streams in four aquatic regimes in terms of their influence over the development of aquatic life is updated from the existing classifications, with stream aquatic regimes defined as Permanent, Temporary-pools, Temporary-dry and Episodic. While aquatic regimes describe the long-term overall variability of the hydrologi-cal conditions of the river section and have been used for many years by hydrologists and ecologists, aquatic states de-scribe the availability of mesohabitats in given periods that Published by Copernicus Publications on behalf of the European Geosciences Union. 3166 F. Gallart et al.: A novel approach to analysing the regimes of temporary streams determine the presence of different biotic assemblages. This novel concept links hydrological and ecological conditions in a unique way. All these methods were implemented with data from eight temporary streams around the Mediterranean within the MIRAGE project. Their application was a precon-dition to assessing the ecological quality of these streams.