Aproveitamento de água de chuva no meio urbano e seu efeito na drenagem pluvial

AUTOR(ES)

Fernando Dornelles

FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

2012

RESUMO

There is an increasing interest from the society in rainwater harvesting and use in urban areas, due to the benefits that this practice provides, such as: economic, environmental and urban flooding control. This interest may be perceived by the emergence of government regulations and increased availability of specific products in the domestic market for the capture, processing and storage of water. Consequently, quantifying the benefits is a key element for allowing the use of rainwater to become popular in the urban environment. Among the measurable benefits, the use of rainwater as a contribution to the reduction of urban flooding is the least discussed; when available, the results are often valid only for specific cases, do not allowing their generalization and application to different scenarios and configurations. The present work was motivated by the scarcity of studies that addressed the effect of the use of rainwater in the reduction of urban runoff, and the lack of design methods that could allow the estimation of performance indicators for the rainwater harvesting and use systems. A graphical design method (using abacuses) is proposed. Abaci were created from the application of the Monte Carlo technique, applied to synthetic series used in the mass balance simulation of rainwater reservoirs, to obtain performance indices as function of the volume and the estimated demand for non-potable water. The abaci were produced for all Brazilian capitals and also the Federal District, in order to verify their applicability to different rainfall regimes existing in Brazil. The use of the graphical design method allowed creating different scenarios and assumptions for designing systems for rainwater use. The combination of these scenarios with observed data of water demand, applied to two different urbanization patterns (low income dwellings and upper class habitation), in the municipality of Porto Alegre, allowed the assessment of the probability of different retention volumes for reservoirs in residential lots. The expected volumes constituted the initial condition for hydraulic simulation of hypothetical watersheds with 10 and 25ha, scale compatible with the residential subdivisions of urban catchments in Porto Alegre, using critical rain durations (1h). The simulation results implied an ineffectiveness in reducing the peak flow, as only a small reduction in the volume of the hydrograph was obatained, with the higher reduction (~ 6% to 75% guarantee) observed for the low-income dwellings. The inefficiency in reducing the peak flow for the rainfall and consumption Porto Alegre characteristics, as well the hydrological characteristics of their urban watersheds, can be explained by the purpose of the rainwater harvesting that is the only meet the demand for water, not ensuring sufficient available volume to cause such effect on the peak flow in the conducts.

ASSUNTO(S)

Água da chuva : captação Águas pluviais drenagem pluvial dimensionamento de reservatorios meio urbano desenvolvimento sustentável

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