ABSTRACT
The 46 large reservoirs plus more than 100 small power plants of less than 2 megawatts constructed in the upper part of the Paraná River Basin have produced irreversible impacts on the river culture, as well as aquatic and terrestrial ecosystems, resulting in fragmentation of habitats, extensive changes in water flows, reduced water quality and declining biodiversity. Economic development in the region was stimulated by the installation of water infrastructure, including construction of a transportation system (Hidrovia do Paraná, or Paraná Waterway) of 2,400 km. There are large-scale multiple uses of the reservoirs, especially for hydropower production and also including navigation, water supply for public use, fisheries, aquaculture of introduced species, recreation and tourism. The total population of the Upper Paraná basin that includes six Brazilian states is about 60 million people. Less than 40% of the domestic wastewater is treated, so the total load of organic matter to the basin is very high. Within the reservoirs along the Paraná Basin, there has been extensive eutrophication, degradation of water quality, sedimentation, fish mortalities and transport of suspended materials. These impacts have economic and social consequences at multiple scales. For example, the costs of water treatment for potability increased 200% in the cities of the basin due to the deterioration of water quality. Integrated management of regional watersheds and reservoirs is a fundamental requirement for the sustainability of the basin. Ecohydrological approaches that integrate ecology and environmental management, intensive reforestation of watersheds and adequate treatment of domestic wastewater are important actions that are needed to reduce eutrophication, halt the deterioration of water quality and slow the loss of biodiversity.
