Experience and Lessons Learned Brief

In the last 50 years, extensive construction of reservoirs in many countries and watersheds in Latin America and particularly in Brazil, has produced a great number of artifi cial systems, which have interfered with the hydrology and ecology of several basins, sub-basins, and large rivers. Most of the reservoirs were built up initially for power generation but lately they have been used for multiple activities, such as irrigation, recreation, navigation, fi sheries and/or aquaculture. In Brazil, there has been large-scale construction of reservoirs for the purpose of hydroelectricity production, as shown in Table 1. At present, approximately 30% of the hydroelectric potential of Brazil is being exploited. Several large-scale hydropower projects are concentrated in the southeastern rivers, specifi cally in the watersheds of the Tiete-Rio Grande, Paranapanema, and Parana rivers, all of them sub-basins of the La Plata Basin (3,000,000 km 2 ). The production of hydroelectricity in Brazil is strategic for the country’s development since approximately 70% of the country’s energy is generated by large hydropower reservoirs. One of the problems, however, is that most of the hydroelectric potential is concentrated in the north, far away from the large urban centers and industrialized regions, demanding extensive transmission lines. These new reservoirs cause impacts on regional and local ecosystems and in the economic and hydro-social cycles. Reservoirs in Brazil, therefore, provide a reference point in river systems since their evolution, changes in water quality and eutrophication, and alterations in fl ora and fauna refl ect existing watershed management, policies and the use of the land system (Straskraba, Tundisi and Duncan 1993). As intermediate systems between rivers and lakes, reservoirs have many mechanisms of functioning and the process of following up their changes is a theoretical and practical study of high signifi cance. The main uses of reservoirs in Brazil are: