Practical design of reservoirs for rainwater use in buildings in Brazil: behavioural analysis and modelling

Abstract

Abstract The new version of NBR 15527 (ABNT 2019) determines that any methodology used for the design of rainwater reservoirs must be performed considering the demand for rainwater resources. Thus, the objective of this study was to develop mathematical models for the design of rainwater reservoirs in residential buildings for all Brazilian states. Different use scenarios were simulated, which included drinking water demands of 100, 150, 200 and 300 litres per capita and rainwater replacement for drinking water at rates of 25, 35, 45 and 55%, according to rainfall data from the last decade. The optimal and maximal volumes of each scenario were calculated using the yield after spill (YAS) behavioural method. Based on the values of the volumes obtained, the studied municipalities were grouped, and for each group, the practical models were adjusted and evaluated using the coefficient of determination (R²) and the root mean square error (RMSE). A good adherence of the models to the observed data was observed, which simplified the estimation of the volume for rainwater reservoirs; practical applications demand that designs use discreet daily rainfall values.