Low flow-duration-frequency models. Concept and use for a regional approach to watershed low-flow regimes in the Loire (France) and Crisu-Alb (Romania) regions

The French Department of the Environment entrusted to the CEMAGREF the realization of a study relating to an ecosystemic approach to the management of the Loire watershed. Over the long term, this approach is designed to establish orientations for the protection and management of the natural aquatic environments of the Loire. To this end, a good knowledge of the variability of the hydrological regimes is necessary. The method presented relates primarily to low flow discharges. In spite of the great heterogeneity in space and time of low flows, a regionalization study of watershed low flow regimes of Loire (S = 117 000 km super(2)) has been attempted on the basis of the same QdF (discharge-duration-frequency) concept developed for floods (GALEA and PRUDHOMME, 1996). To allow an objective evaluation of developed methodology, we present here the details of the conceptual approach used to model and synthesize the low flow regimes observed, and present the results obtained.