production at Water course scale [*] Alterach Julio*, Peviani Máximo*, Elli Alberto*, Davitti Alessandro* 13th IWRA World Water Congress 2008, Montpellier – Francia, 1-4 Settembre 2008 * CESI RICERCA The identification of the potential hydropower at river scale (within a single basin) needs a precise analysis of the water availability in terms of annual stream discharge duration curve coupled with available geodetic falls. The paper presents a GIS integrated numerical tool that allows for the evaluation of the residual potential hydropower energy and all possible alternatives concerning the sites for hydroelectric plants along the drainage network, taking into account the relationship between the full costs of the mini-hydro power and the benefits from selling the generated power in the national market. The tool takes into account the water resources present exploitation with its geographical location and elevation (with respect to irrigation uses, drinkable water, existing hydropower plants, etc.), and the limitation that this creates regarding the potentiality for energy production. The software is based on the topographic information (Digital Elevation Model) and the isohyets maps, with a whole analysis of the catchment, together with the regional evaluation of available discharges along the river system. Based upon a user friendly graphical interface the tool is able to split the river into a hundreds of cross sections and to calculate the available discharges and potential hydropower production, considering constrains like minimum flow, withdrawals and restitutions scheme. The tool shows to be a quite powerful instrument to support decision makers and stakeholders, for preparing energy plans, assess potential sites and implement small scale hydropower plants. [*] This work has been financed by the Ministry of Economic Development with the Research Fund for the Italian Electrical System under the Contract Agreement established with the Ministry Decree of march 23, 2006.