Definition of Ecological Flow Using IHA and IARI as an Operative Procedure for Water Management

It is widely recognized that the hydrological regime of natural flow plays a primary and crucial role in influencing the physical condition of habitats, which, in turn, determines the biotic composition and sustainability of aquatic ecosystems. The current hydro-ecological understanding states that all flow components might be considered as operational targets for water management, starting from base flows (including low flows) to high and flood regimes in terms of magnitude, frequency, duration, timing, and rate of change. Several codes have been developed and applied on different case studies in order to define common tools to be implemented for Eflow assessment. This work deals with the definition of an operative procedure for the evaluation of the Eflow monthly distribution to be adopted in a generic watercourse cross-section for sustainable surface water resource management and exploitation. The methodology proposes the application of the Indicators of Hydrologic Alteration methodology (IHA by TNC) coupled to the valuation of the Index of Hydrological Regime Alteration (IARI by ISPRA) as an operative tool to define the ecological flow in each monitoring cross-section to support sustainable water resource management and planning. The case study of the Agri River in Basilicata (Southern Italy) is presented. The analyses were carried out based on monthly discharge data derived by applying the HEC-Hydrological Modeling System at the basin scale using the daily rain data measurements obtained by the regional rainfall gauge stations and calibrated through the observed inlet water discharge registered at the Lago del Pertusillo reservoir station.