Lucio Di Matteo, Carlo Cardellini, Stefano Casadei, Corrado Cencetti, Massimo Lorenzoni, Antonella Carosi, Luca Bartoletti, Costanza Cambi, David Cappelletti, Roberto Checcucci, Rita De Filippis, Pierluigi De Rosa, Andrea Fredduzzi, Francesco Frondini, Flaminia Guerrieri, Alex Manucci, Sofia Ortenzi, Marco Stelluti, Sara Taviani, Mauro Tieri, Daniela Valigi
Estimating ecological flows is essential in rivers to achieve the objectives defined by the EU Water Framework Directive 2000/60/EC (WFD). In the framework of an agreement with the Autorità di Bacino Distrettuale dell’Appennino Centrale, the work aims to present the results of an integrated approach developed to consider various factors affecting the river’s ecological flow (hydrological, hydrobiological, hydrogeological, hydro-morphological, and hydrochemical). The present study focuses on the Nera River, a main tributary of the Tiber River, which is primarily fed by groundwater from limestone aquifers. The river catchment hosts strategic water resources that are crucial for providing drinking water and sustaining aquatic ecosystems. Moreover, river water is utilized for hydropower generation, fish farming, and various recreational activities along the river. The ecological status was rated as good based on the New Index of the Ecological Status of Fish Communities (NISECI), along with physicochemical characterization of river water and hydromorphological characteristics as criteria for its definition. Based on a regional model specifically developed for brown trout of rivers in the Tiber River basin (thus applicable to the Nera River), the minimum ecological flow was set at approximately 2.92 m³/s. Based on flow-duration curves, the average and maximum ecological flow values were also identified as 3.71 and 5.07 m³/s, respectively. The analyses carried out by the Water Exploitation Index Plus (WEI+) revealed medium-to-high stress in the catchment; therefore, withdrawals should be carefully re-planned to minimize further impacts on water-dependent ecosystems. The approach proposed for the Nera River highlights the importance of conducting focused, multidisciplinary studies in areas where groundwater withdrawals interact with groundwater-dependent ecosystems, thereby supporting regional management plans that address the needs of both humans and aquatic ecosystems.