Author(s): Comoglio Claudio; Enrico Pini Prato; Rosso Maurizio
Linked Author(s): Claudio Comoglio
Keywords: Fish pass; Weir rehabilitation; Environmental flow; Marmorata trout; Po river
Abstract: The retrofitting of dams and weirs, in compliance with the legal requirements concerning environmental flow release and fish pass construction, can lead to high costs for the infrastructures owners and managers, from the designing, construction and management to the monitoring and maintenance of the devices, but also, and above all, because of the consequent lack of use of the relative discharges. These conditions are even more problematic in situations where the environmental requirements relative to the aforementioned obligations have only recently been applied, as is the case in Italy. This paper presents the main characteristics of a recent project for the construction of a fish pass at La Loggia weir on the Po river that fragments the river continuum with a 7. 0 m drop. A design solution has been identified, in this case study, that is able to satisfy environmental flow release obligations through the construction of a vertical slot fish pass with a design discharge of 0. 79 m3/s whose attractiveness is guaranteed by an auxiliary flow of 10 m3/s (i. e. the entire compulsory environmental flow) which passes through the turbine of a small hydropower plant that has been installed at the site. This plant is able to guarantee a mean annual electric energy production of about 3. 5 GWh/year. The project at La Loggia weir is one of the most important rehabilitation projects of existing weirs in this field in Italy. This work, which is mainly destined to the upstream migration of marmorata trout (Salmo trutta marmoratus), an endemic fish species of the Po river watershed, is foreseen in an area of relevant ecological and environmental value on the most important river in Italy and it will be set up with a monitoring room equipped for scientific studies, guided visits and environmental teaching projects.
Year: 2007