The research aimed to quantify river ecosystem services. In particular, we focused on three services depending on the river flow regime: a recreational services, the white-water rafting, an habitat provisioning service, the habitat for the marble trout and a provisioning service, the energy produced by small hydropower plants. The river selected for the study is a gravel-bed Alpine River, the Noce River which is in Trentino region in North Eastern Italy. This river is one of the best in the world for white-water rafting according with National Geographic, it provides habitat for the marble trout (Salmo trutta marmoratus) which is a specie included in the Habitat Directive, and it is a river heavily exploited by both large and small hydropower production. The services are in conflict and a methodology to quantify their mutual effects is necessary. Firstly, we computed water depth and water velocity with a hydraulic model. Secondly, using habitat suitability concepts, we applied preference functions to hydraulic parameters and compute the suitability and suitability thresholds of each service at different stream flows. Thirdly we applied these thresholds to different flow patterns calculated with an hydrological model, to evaluate the variation in time of the suitability.

The key driver of the flow regime and consequently of the suitability for the studied services in the Noce River is the large hydropower production, which is necessary to guarantee white-water rafting navigability especially during the summer months and it has a limited effect on adult trout habitat. In addition, we included in the river system several future withdrawals for small hydropower production. We simulated different flow management alternatives by optimizing in turn the requirements for each ecosystem services. The method permits to evaluate the effects of different withdrawals in different flow regime alternatives and it can be a support system to help river managers.