Case study on river management: São João
The São João River itself is 120km long and flows from mountains and hills to a broad coastal plain with numerous ponds and lagoons, including the 220km² Lake Araruama, the largest coastal saline lagoon in Brazil.
The marine zone adjacent to the river mouth is notable for resurgence of nutrient-rich marine water, which supports a rich fish fauna and the southernmost occurrence of coral in Brazil.
The basin contains eight municipalities and about 100,000 people live in the region.
The main economic activities are real estate, beach tourism and fishing in the coastal strip, and agriculture and tourism (ranch-style hotels) in the rural hinterland.
The extraction of salt from Lake Araruama, formerly an activity of great importance, is nowadays in decline.
And during the 1970s, the government dammed the São João River at Juturnaíba Lake, which was enlarged from 8km² to almost 40km², thereby creating a large reservoir.
This became the main source of water for several cities, including some of Brazil's top beach resorts. During the tourist season, the local population is at least doubled.