The values of the criticality in the basins investigated in this WEHI-539 study ranged from 1 to 6. The criticality is 0 for 64 river branches and greater than 3 (which is considered significant) in 24 stretches, mainly those belonging to the Vomano (7), Liri-Garigliano (5) and Sangro (5) basins.
To avoid overestimating the annual electricity production for river branches with significant values of criticality, the flow duration curves produced by the regionalisation procedure were corrected by holding constant the mean annual flow rate. Therefore, the regional flow duration curves of certain river branches are rotated about Qm in such a way that the flow rate is less than or equal to the hydrological component of the minimum vital flow for a period corresponding to the value of the criticality.
Fig. 5 compares the flow duration curves for a river branch in the Saline basin resulting from the regionalisation procedure with and without the correction, taking into account the effective value of the criticality, which is 3 for the case examined. As shown, by rotating about the mean value (Qm = 1.62 m3/s), the corrected FDC shows a flow rate coincident with the hydrological component of the MVF (Q∗ = 0.2 m3/s) for a duration of 75%, corresponding to a criticality of 3.