HYDROPOWER GENERATION AND RIVER ECOLOGICAL STATUS: SUSTAINABLE MANAGEMENT SCENARIOS

River systems provide essential services to human activities, the so-called ecosystem services. However, due to anthropological activities, such as dams, water withdrawals, or defensive works, they are often subject to hydromorphological pressures. In order to preserve their ecological status and to ensure an appropriate water management, a legislative framework that considers this conflict is necessary. In Europe, the Water Framework Directive, WFD, (European Commission, 2000), has been introduced with this aim. Within this context, the concept of environmental flow (e-flow) has been developed and it has been defined as the hydrological regime that allows to achieve a good ecological status of the water body. To correctly define e-flows, habitat modelling has been widely used all over the world. In Italy the methodology used to define the e-flows is the Mesohabitat Simulation Model (MesoHABSIM, (Parasiewicz, 2001), which assess the river habitat suitability for target species at the morphological unit scale (or the meso-habitat scale). The methodology has been included to the Italian legal framework with the ‘Manuale tecnico-operativo per la modellazione e la valutazione dell'integrità dell'habitat fluviale’ (Vezza, Zanin, & Parasiewicz, 2017) and the Ministry Decree DD n. 30/STA 2017. This master thesis work consists in the application of the MesoHABSIM methodology to the Dora Baltea River in the Aosta Valley, Italy. The selected river reach is located close to Morgex, where a new, hypothetical hydropower plant is currently under design. The aim of this thesis is to simulate the water withdrawal management system that allows to optimize the power generation and, at the same time, to preserve the ecological quality of the river habitat. The work is composed by two parts. The first one has been focused to quantifying the area suitable for some target species in different discharge conditions, obtaining the so-called Habitat – Flow Rating curve that relates the flow rate in the river with the aquatic habitat availability by using the SimStream-Web Platform. The second part of the thesis aimed at evaluating different water management scenarios that ensure an economically sustainable power production and minimize the ecological impacts on the aquatic habitat. Also those analysis has been performed by means of SimStream-Web Platform, a web service developed by the Politecnico di Torino for the MesoHABSIM model applications. The comparison between different water management scenarios has been based on the Habitat Integrity Index (IH) as a metric that quantify the deviation between reference and future altered conditions. The most suitable management option has been chosen as the one with an IH greater than 0.6, meaning the preservation of a good ecological status.