Tropical reservoirs upstream from hydroelectric dams are known to release significant amounts of methane to the atmosphere. Here we demonstrate that methane emissions downstream from hydroelectric ...dams can also be large. Emissions of CH4 downstream of Balbina reservoir in the central Amazon basin (Brazil) were calculated from regular measurements of degassing in the outflow of the turbines and downstream diffusive losses. Annual emissions from the reservoir surface and downstream from the dam were 34 and 39 Gg C, respectively. The downstream emission alone represented the equivalent of 3% of all methane released from central Amazon floodplain.
Hydroelectric reservoirs can release significant quantities of CO2, but very few results are available from the tropics. The objective of the present study was to estimate the emission of CO2 from ...the Balbina hydroelectric reservoir in the central Brazilian Amazon. Diffusive and ebullitive emissions were estimated at regular intervals, both above and below the dam, using a combination of static chambers and submerged funnels. Gas releases immediately below the dam were calculated as the difference between gas flux at the entrance and the outflow of the hydroelectric turbines. An inundation model derived from a bathymetric map and daily stage readings was used for spatial and temporal interpolation of reservoir emissions. Annual emissions of CO2, upstream and downstream of Balbina dam for 2005, were estimated as 2450 and 81 Gg C, respectively, for a total annual flux of 2531 Gg C. Upstream emissions were predominantly diffusive with only 0.02 Gg C yr−1 resulting from ebullition. On average, 51% of the downstream emission was released by degassing at the turbine outflow, and the remainder was lost by diffusion from the downstream river. The total annual greenhouse gas emission from Balbina dam, including the CO2 equivalent of previously estimated CH4 emissions, was 3 Tg C yr−1, equivalent to approximately 50% of the CO2 emissions derived from the burning of fossil fuels in the Brazilian metropolis of São Paulo.
Key Points
Annual CO2 emissions from Balbina Dam in the Brazilian Amazon were quantified
Emissions below the dam were significant
Reservoirs could contibute significantly to anthropogenic CO2 emissions
Carbon dioxide (CO
2
) and methane (CH
4
) generated in reservoirs are released downstream of dams, and few studies have considered these downstream emissions. Fluxes downstream of 3 Amazon ...hydroelectric reservoirs (Tucuruí, Samuel, and Curuá-Una) are reported here. Degassing through turbines was calculated as the difference between intake and outflow concentrations. Additional releases along the Tocantins, Jamari, and Curuá rivers were measured at downstream sites over a distance of 30 km. About 50% of the CH
4
and 30% of the CO
2
emitted downstream of the dam were liberated at the turbine outflow. The total downstream emissions are sufficiently large to require consideration in assessments of greenhouse gas emissions from hydroelectric reservoirs.
Oceanic islands are highly vulnerable to environmental changes. Thus, the vegetation mapping of these systems are of fundamental importance. The objective of the present work was to study the ...composition and distribution of plant species to classify and describe the vegetation types of the islands of Abrolhos (Santa Barbara, Siriba, Sueste, Redonda and Guarita) in southern Bahia during August, October and December 1995 and in March and May 1996. The isolation of the archipelago from the mainland and its structural features offer a great potential for geographic studies. The spatial distribution of seven vegetation types (after beach, after rocks, mild slope, sheer slope, top shrub, top herb, top grass) were delimited, using as indicators physiognomy, relief and floristic composition. The vegetation types were classified according to their geographic characteristics and vegetation structure, were associated to the 40 species identified.
As ilhas oceânicas são altamente vulneráveis à modificação ambiental. Por isso, os trabalhos de mapeamento de vegetação são de fundamental importância. O objetivo do presente trabalho foi de realizar o estudo florístico e o mapeamento, a classificação e a descrição dos tipos de vegetação nas ilhas do Parque Nacional Marinho de Abrolhos (Santa Bárbara, Sueste, Siriba, Redonda e Guarita) em agosto, outubro e dezembro de 1995 e março e maio de 1996. O arquipélago se situa no sul da Bahia e devido às suas características estruturais e ao isolamento em relação ao continente oferece um grande potencial para estudos geográficos. Foram delimitadas as distribuições espaciais de sete formações vegetais encontradas (pós praia, pós rocha, encosta suave, encosta íngreme, topo ciperóide, topo herbácea, topo graminóide) usando como principais indicadores fisionomia, relevo e composição florística. Os tipos de vegetação foram classificados segundo características geográficas e estrutura da vegetação, sendo associados a 40 espécies identificadas.
The trade traffic estimate was made by using real data from 2 years of seizures (2000 and 2001), combined with river stage-level data. Abufari Reserve is located about 600 km south of Manaus, where ...the largest stretch of the Amazonian floodplain is protected by a federal conservation unit. In the minds of the local people, the chelonian populations are still abundant and inexhaustible. However, records show that in 2000 and 2001, 3992 chelonians and 122 Podocnemis nets were confiscated, which represent only a small part of the total catch from this river. Consequently, these natural stocks could be decreasing because of trafficking by animal peddlers who invade the area and escape with animals to the detriment of the ecosystem and the local people.
PDF
