Avaliação de Alternativas para Reabilitação de Lagos Urbanos: O Caso da Lagoa da Pampulha, em Belo Horizonte – MG

Abstract

Lagoa da Pampulha is an artificial lake located in the city of Belo Horizonte and has been suffering for decades with problems of eutrophication and silting. For almost 20 years, several actions have been implemented, seeking to promote the rehabilitation of the lake. However, Lagoa da Pampulha still shows signs of degradation. In this context, the objective of this work was to evaluate the importance of sanitary, environmental and urban improvements, implemented in the hydrographic basin, in the rehabilitation process of Lagoa da Pampulha. For this purpose, calculations of the total phosphorus (TP) and total suspended solids (TSS) loads contributed annually to Lagoa da Pampulha, obtained from hydrological and water quality monitoring data between the years 2016 and 2017. In addition, modeling was performed using the Storm Water Management Model - SWMM to evaluate the production of TP and TSS loads in hypothetical scenarios. The conservative scenario proposed a reduction of 50% in the discharge of sanitary sewage in water courses and an increase of 30% and 10% in the area of urban areas and non-vegetated soils, respectively, in the hydrographic basin. In an optimistic scenario, a reduction of 95% in sewage releases and a reduction of 50% in non-vegetated soils was proposed. Finally, the impacts of the calculated and simulated loads in Lagoa da Pampulha were analyzed by means of the Trophic State Indices and the Silting Rate. ndicated that, even with the implementation of the proposed measures, the loads brought to Lagoa da Pampulha by surface runoff remained quite high, ranging from around 23.000 to 13.000 ton / year for the conservative and optimistic scenarios, respectively. Both the calculated loads and the simulated loads were translated into Trophic State Indices greater than 70, with a hypereutrophic classification for Lagoa da Pampulha, associated with a severe eutrophication process This evaluation allowed us to infer that the improvements in sanitary conditions and land use in the hydrographic basin, despite their relevance, do not alter in the medium and short term, the condition of degradation of the lake, needing to be associated with other rehabilitation techniques. The results of the TSS calculations and simulations indicated a TA of around 7.000 to 5.000 m3 / year, values that differed from the rates obtained by means of topobatimetry, greater than 100.000 m3 / year. Thus, it was not possible, in this work, to relate the TSS load in the silting process of Lagoa da Pampulha.