The imbalance instead derives from the fact that any derivation imposes missed opportunities on other potential users. This may be the case – for example – of derivations for hydroelectric purposes: projects that are often criticised due to the strong alterations to the hydrological regime of watercourses, which in natural conditions could instead provide various other services (often recreational).
The decision to enforce the ecological flow downstream of the derivations, which from a quantitative point of view increases – almost everywhere – of the current minimum vital flow, seems therefore correct. A flow value calculated on a purely hydrological basis cannot guarantee a correct balance in the provision of services, much less – if it is too low – the conservation of aquatic ecosystems capable of providing these services.
Among the subjects that will have to deal with this problem, there are the consorzi di bonifica (Italian public bodies dedicated to the management and improvement of water plants). In fact, their large derivations are functional for public interest purposes such as the permanence of irrigated plain areas with an agricultural vocation. A study conducted by Etifor for the Consorzio di Bonifica Piave shows how, in parallel with the irrigation service, other Ecosystem Services linked to the very existence of consorzio derivations are to be considered of “public interest”. Evaluated and weighed from an economic point of view, services such as groundwater recharge, water purification, habitat supply, carbon fixation, aesthetic-landscape service and tourism-recreational service can also be compared with those of irrigation or hydroelectric supply, which might appear as more important because they are part of the traditional market.
If we imagine also evaluating the other side of the coin, i.e. the community benefits due to the reduction/zeroing of large derivations (with consequent improvement of the river ecosystem), then the results could be compared to verify which use of surface water can bring balance in the provision of Ecosystem Services. The assessment of Ecosystem Services can thus benefit the definition of ecological flow, complementing river habitat modelling with a full recognition of the services provided to all territorial actors involved.