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.