Proposal of rainwater harvesting coefficient (RWHC) for determination of effectively usable rainfall depth, relevant to rainwater harvesting systems design

Abstract

ABSTRACT The study measures rainfall data to determine a rainwater harvesting coefficient revelant to rainwater harvesting and catchment projects assisted by non-parametric statistics tests, based on assumption that part of the total rainfall depth is discarded. The analyses of historical rainfall series shows that the city of Belem presents large potential to promote rainwater harvesting, with a rainy season and a less rainy season during the year. The results present an average of one rainfall event per day, from January 2001 to December 2011, and of which around 38% is used only for washing the rainwater harvesting system. The Anderson-Darling test revealed a non-adherence of the rainfall series to a normal distribution and according to the Mann-Kendall test, there was no significant trend in the evaluated series. After the calculation of the effective rainfall, determination of coefficients, application of the Anderson-Darling normality test and the Kruskal-Wallis variance test, it was proposed a rainwater harvesting coefficient of 0.78 for the city of Belém, Brasil.