The software we propose enables users to test several water allocation rules (both static and dynamic) for a specific small hydropower plant and to evaluate them both in term of economic and ecological benefits. For each water allocation rule the energy produced and the impact on the ecosystem are calculated. This latter quantity is estimated in term of fish habitat suitability and preservation of the natural streamflow variability. The input data necessary to the software must be entered from the first window (figure on the right) and are divided into four categories: river hydrograph, hydropower plant data, ecosystem data, and water allocation policies.