Amazonian Reservoir Research Articles

Methane, carbon dioxide and nitrous oxide emissions from two Amazonian Reservoirs during high water table

Methane, carbon dioxide and nitrous oxide emissions from two Amazonian Reservoirs during high water table

Reservoir Management in South America

There has been a rapid increase in the number and size of reservoirs in all continents. In South America some hydrographicbasins such as the la Plata are almost completely exploited whereas others such as the Amazon are just starting to be exploited for hydropower energy. Ecological studies at the newly created artificial lakes were carried out from the filling phase and extending some years after, in order to understand the functioning of the lakes, the problems arising from the impoundment and to explore the possibilities of applying cheap ecotechnology as corrective measures. The studies in the Amazonian reservoirs have shown that oxygen depletion and nutrient accumulation are a serious problem in lakes with dendritic shape and long residence time. Clearing biomass prior to impoundmentand new engineering designs for water oxygenationmust bc developed. Results from la Plata basin reservoirs show that eutrophication, toxic contamination and siltation are widespread problems which must be corrected by pollution and erosion control.

Arthrospira skujae, a New Planktic Tropical Cyanoprokaryote

Summary Two populations of cyanophytes that produce screw-like coiled trichomes were examined in order to elucidate their taxonomic position. The first population was collected in an Amazonian reservoir in June 1989. From the investigations of this species, it was possible to establish a new species of Arthrospira (A. skujae) that had previously been classified by Skuja (1949) from Burma under the name “ Spirulina gigantea ” (sine typo). The second, similar population was collected in the littoral zone among water plants, of a small, shallow pond in the southeastern part of Brazil, which corresponded to Arthrospira jenneri . Both species were evaluated statistically, and the measurements, drawings, photos and comparisons with closely related species are presented.

Hydroelectric dams in Brazilian Amazonia: response to Rosa, Schaeffer & dos Santos

In a critique of my paper on ‘greenhouse’ gas (GHG) emissions from Amazonian reservoirs (Fearnside 1995), Rosa et al. (1996) suggest that I have reached overly pessimistic conclusions because the reservoirs on which my calculations are based are unrepresentative and because methods based on the Intergovernmental Panel on Climate Change's (IPCC) global warming potentials (GWPs) are unfair for comparing hydroelectric and fossil fuel options. I rush to defend my analysis.

A model for decomposition of the drown vegetation in an Amazonian reservoir

The terrestrial vegetation is in most cases not removed before filling of an Amazonian reservoir, causing oxygen problems due to decomposition of organic matter. This work describes an oxygen model of Amazonian Reservoirs, focusing on the role of decomposition of organic matter originating from drown vegetation in the oxygen balance. The model encompasses the following state variables: three fractions of organic matter accounting for differences in biodegradability, dissolved oxygen and ammonium. The temperature is also considered to account for the stratification. The model has been tested on a case study, Tucurui Reservoir, which has a surface area of 2430 km2 and a volume of 45 km3. The residence time is 45 days in average. The filling started in September 1984 and it is estimated that the drown vegetation was 40 billion tons of carbon. The model results have been compared with measurements of oxygen taken close to the dam. The modelled oxygen and temperature profiles showed a reasonable agreement with the measurements at two different hydrological conditions, i.e., at high and low water conditions. The modelled results of ammonium showed, however, a too small concentration in hypolimnion during anoxic conditions probably due to an underestimation of the anaerobic release rate for ammonium from the sediment to the water column.