Fitting and suitability of mathematical models for the practical design of rainwater harvesting reservoirs for the state of Minas Gerais, Brazil

Due to the complexity, and variety of results obtained, depending on the design methodology chosen, the rainwater reservoir design is often carried out in an empirical way in Brazil. As an attempt to disseminate a practical and accurate design method, this study performed the sizing of rainwater reservoirs using the Yield After Spill (YAS) algorithm, then fitting mathematical models to the obtained results, using as independent variables: statistical parameters related to rainfall, the demand for non-potable water and the rainwater catchment area, for all the mesoregions of the State of Minas Gerais, Brazil. It was observed that from a certain value of demand for non-potable water, there was a change in the behaviour of the obtained reservoir volumes. Thus, it was necessary to divide the results into two behaviour regions––with ascending and descending trends. In general, for the first and second behaviour regions, a better performance was reached for the exponential and power models, respectively, measured by the coefficient of determination (R2). With these results, water resources technicians will be able to design the rainwater reservoirs in a simple and accurate way, avoiding unnecessary costs, such as the purchase of a reservoir with a larger volume than necessary or the expansion of the storage capacity.