Author(s): Markus Reiber; Nilo De Oliveira Nascimento; Brigitte Helmreich
Linked Author(s): Nilo De Oliveira Nascimento
Keywords: Rainwater harvesting; Socio-economic; Large-city scale; Cost-benefit; Rainwater potential
Abstract: Depending on precipitation intensity, rainwater constitutes a potential source of drinking water. Therefore, rainwater harvesting systems are already used in some countries, but large-scale implementations are not frequent, particularly in the urban environment. This paper describes estimations on the reduction of potable water consumption by large scale implementation of domestic rainwater harvesting systems, taking the municipality of Belo Horizonte (Brazil) with a population of 2. 4 million inhabitants as a case study. The research adopts an approach, which combines socio-economic information (e. g. family income, number of family members) with dwelling characteristics (e. g. roof area, area of permeable and impermeable surfaces) and potable water consumption in relation to family income. The available precipitation water volume for each construction was determined by means of the building details of twelve predefined building standards (detached and apartment buildings), which can be compared to the variability of construction characteristics in Belo Horizonte. A 22-years’ time series of daily precipitation amounts was applied for the estimation of the rainwater volume available. The use of rainwater was limited to toilet flushing, irrigation, and cleaning. Long term simulations for the operation of rainwater systems were performed for each of the twelve predefined buildings, in a process aiming at system storage capacity optimization. The determination of the system’s costs and benefits allowed utilizing a cost-benefit analysis to evaluate the system viability and balancing the rainwater availability as well as to determine the demand for non-potable water, rainwater harvesting capital, operation costs and corresponding reductions on the drinking water bill. Combining predefined building characteristics and the associated potential for drinking water savings and socio-economic data for each district in Belo Horizonte allowed estimating the potential of reducing drinking water consumption for the whole municipal area.