Contribution to the Defining of the Minimum Acceptable Flow, Tiber River Basin Authority Experience

This article refers to the results of the experimental campaign promoted by the Tiber River Basin Authority during the period from March 1997 – March 1998, aimed at the quantitative definition of minimum acceptable flows. Two operative units from the University of Perugia with scientific experts in fluvial depths, hydro-biology and biology took part in the work group. The data gathered in the field regarded the depth, ichthyic, morphological and chemical-physical charac-teristics of 14 reaches of the river network. These reaches were carefully selected to represent the river types found most frequently in the middle-upper Tiber River basin, where there were no sig-nificant contributions of anthropic or industrial pollution. The areas sampled covered approximately 6.000 km2 and regarded the river zones populated prevalently by rheophilic cyprinids (barbel zone) and salmonids (trout zone). The results obtained generalized the approach known as the IFIM method and permitted an evaluation of the flows that maximize the river habitat (Qott) for the relevant fish species.