Influence of the accumulated precipitation and the spatial distribution of rainfall on the results of reservoir sizing methodologies

In this article, we analyze the behavior of six methodologies for dimensioning rainwater reservoirs present in Brazilian standards (Rippl, Simulation, Azevedo Neto, English, German, and Australian), aiming to evaluate the influence of precipitation variability in the results provided by these methodologies. The strategy was to submit the same case to the precipitation characteristics of 65 Brazilian cities. In this way, the methodologies were subjected to the characteristic of similar annual rainfall distribution and different accumulated annual rainfall. And subsequently subjected to different rainfall distributions, but next annual accumulated rainfall. These comparisons show that the influence of rainfall distribution regimes is the main factor for efficient sizing. How rainfall is distributed over the year is more relevant to the dimensioning than the cumulative total. Thus, sizing methodologies that consider changes in rainfall distribution throughout the year tend to be more efficient in meeting the demands of a rainwater catchment project. Methodologies that neglect the relevance of rainfall distribution are likely to provide under-or over-dimensioned results.