Uncertainties in flow duration curves in anthropized catchments

Flow Duration Curves (FDC) are a traditional tool in water resources management. Their applications range from environmental protection planning to hydrosystems design. In many problems natural FDC are needed, that is curves referring to river regimes before alterations due to anthropic water uses. Estimation of FDC, as known, is uncertain in ungauged catchments. Also in gauged catchments, however, uncertainty may be relevant if available flow data are few or recorded after the anthropic alterations were set. This uncertainty may be high in mountain rivers, whose regime is typically more irregular and with significant alterations, mostly due to withdrawals for hydropower uses. The scope of this paper is to analyze these uncertainties, using a methodology to link anthropic uses to FDC alterations. Application to a catchment in the southwestern Alps is finally presented.