Possible water uses in mining lakes: case study of Aguas Claras, Brazil

The paper presents a Brazilian experience related with the decommissioning of an exhausted mining activity and the consequent formation of a pit lake. This water body, which is still in a process of filling, will reach the final depth of 234 m, being hence the deepest lake in the country. Since 2001 (first year of formation) the water quality has been monitored on a monthly basis. The aquatic environment is absolutely free from contamination and presents an excellent water quality. There is a marked shift in the dominance of algae groups, probably due to this early stage of creation of a new ecosystem. Some conflicts are now arising regarding the possible water uses. The high water quality allows a sound utilization for urban supply, but the manifestations of the population (through public hearings) is towards the utilization of the lake for recreational purposes and landscape harmony. The paper discusses the origin and possible solutions for these conflicts

Restoration of Lake Pampulha, Brazil by using sanitation and in-lake techniques

The paper presents a broad view about the measures for restoration of Lake Pampulha, Brazil. This man made reservoir is located in a dense inhabited urban area and constitutes the main touristic attraction of the city of Belo Horizonte. Since several decades the water body receives the discharge of untreated sewage from domestic as well from industrial sources, what leads to severe episodes of algal blooms in the water surface. In order to combat this eutrophication problem some measures have been already carried out and others are planned in a short term. These preventive and corrective techniques provides an efficient association between sanitation processes and the application of in-lake treatment actions. Moreover a hydrodynamic modelling has been also carried out with the purpose of evaluating the water circulation and the water residence time in the compartments of the lake

Influence of climatic conditions on cyanobacteria blooms in a tropical water supply river (Rio das Velhas, Brazil)

The paper presents a discussion about the striking influence of climatic conditions on the onset of cyanobacteria blooms in a warm water river in Brazil. An unusual drought period has been observed in the second half of 2007 in Rio das Velhas, Brazil, which led to an unexpected bloom of bluegreen algae (cyanobacteria). Cyanobacteria blooms constitute a special concern in Brazil, since the first human deaths caused worldwide by cyanotoxins have been reported in this country. The Brazilian legal framework restricts the water abstraction under such conditions and imposes a special monitoring programme to be carried out by water supply companies. The results of water quality analysis point out the conjunction of two factors as the main cause of the mentioned cyanobacteria blooms: nutrients input from treated and untreated sewage as well from diffuse sources and the extended dry period in 2007

Sustainable use of low flow reaches downstream energy generation dams

The paper describes the issues of water quality in low flow reaches downstream energy generation dams. These reaches should maintain a minimum water flow in order to guarantee adequate ecological conditions in the water body. A case study is presented with respect to the longest low flow reach in Brazil, focusing mainly on environmental and regulatory aspects. Water quality in this reach should be enhanced by the construction of some intermediate dikes, which will allow the sedimentation of particulate matter and the formation of small reservoirs for the growth of aquatic species. A concern remains only with phosphorus concentrations, since the environment will change from a lotic to a lentic condition

Cyanobacteria in water supply reservoirs and strategies for their control

The paper describes the problems related with eutrophication in water supply reservoirs. One of the most relevant impacts is the growth of cyanobacteria, which are able to generate very powerful toxins. This situation is more critical in tropical regions, where all metabolical processes are faster and where generally there is lack of financial resources for implementation of adequate monitoring programs. A case study(Vargem das Flores Reservoir) is presented, with emphasis on the study of eutrophication development based on N/P relationship. It was found that low N/P values did not favour here the dominance of cyanobacteria, as generally reported in the technical literature. The paper also discusses the adoption of some preventive and corrective techniques for avoiding cyanobacteria blooms in water supply reservoirs

Community response to the restoration of an urban lake

Community response to the restoration of an urban lak

Water quality in semi-arid Brazilian reservoirs

Water quality in semi-arid Brazilian reservoir

Water quality in mining lakes

Water quality in mining lake