Broa Reservoir is a man-made lake at the centre of San Paulo State of Brazil created in a tropical savanna (cerrado) region in 1936 by damming up the Itaqueri River, a small tributary of the Rio Parana. At present, however, the lake is turned into an area of environmental protection because of its importance as a recreation area of scenic beauty and of scientific activities in and around the lake. Large scientific and educational projects are now in progress.

The lake is 7.5 km long and has a very flat basin with a mean water depth of 3 m. A maximum depth of 12 m is observed near the dam site. The water level fluctuates within a range of 1.5 m, being high in April at the end of rainy season and low in September at the end of dry season.

A large portion of its catchment area is covered by sandy soils. which are very aged and extremely infertile. The lake water is also oligotrophic and low in nitrogen level, and certain heavy metals often limit phytoplankton production.

Since the lake is located only 100 km apart from large reservoir systems of S. Paulo State and its water remains relatively free from eutrophication and pollution, it serves as an important standard system for comparison with the large eutrophied reservoirs. The limnology of this reservoir was opened by Brazilian scientists in 1971. Several climatological, hydrological, biological and water chemistry aspects were studied. The researches also cover the ecology, physiology and chemistry of almost all organisms present in the lake. The number of scientific papers so far published regarding this lake now amounts to approximately 200. including several masters and doctoral theses prepared at the University of S. Paulo and Federal University of S. Carlos. The Centre for Hydrological Researches and Applied Ecology, University of S. Paulo, is currently engaged in scientific projects including the modelling of Broa Reservoir system. Educational programs using the lake area as a natural laboratory have also started since 1985 (Q3, Q1, Q2).