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

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.

Influence of rainfall and design criteria on performance of rainwater harvesting systems placed in different Brazilian climatological conditions

“…From Figure 4 it is possible to observe that for the same storage tank volume, the failures on demand-supply are greater when the first-flush diverter is considered by comparing with a non-diverter system, agreeing with results presented by Corrêa et al (2018) and Semaan et al (2020). Specifically, for the 200 m 2 rooftop area, the introduction of a first-flush diverter means to discard a volume that can reach 0.4 m 3 every 7 days.…”

“…The analysis accomplished indicated that daily rainfall time series are suitable for RWH system design in the evaluated cities and were also adequate for Belém, State of Pará, Brazil (Corrêa et al, 2018). The use of daily rainfall time series is also an international recommendation, as stated by Campisano et al (2017).…”

“…The planning of the RWH system is influenced by a series of socioeconomic, environmental and technical factors such as the rainfall regime, rainwater quality, space availability, required demands and its characteristics, criteria for project, among others (Santos & Taveira-Pinto, 2013;Melville-Shreeve et al, 2016;Martínez-Acosta et al, 2019;Vargas et al, 2019;Toosi et al, 2020). Therefore, it is difficult to find a basic and generic recommendation for the size and configuration of rainwater storage systems (Jones & Hunt, 2010;Campisano et al, 2017;Corrêa et al, 2018;Semaan et al, 2020), especially in regions and countries, such as Brazil, where the large climatic variability can affect the RWH performance (Palla et al, 2012;Sahin & Manioglu, 2019, Pacheco et al, 2017.…”