Comparative study between design methods for reservoirs of rainwater harvesting and use systems

Abstract

The imbalance between the increasing demand for water in the various human activities and the pronounced scarcity of water make up the panorama of a national water crisis. Actions such as the capture and use of rainwater are an alternative to scarcity. However, the design of the reservoir that integrates Rainwater Harvesting and Use system (RHUs), comprises a complex step, given the existence of several methods that result in differentiated volumes, according to NBR 15527 (ABNT, 2007), namely: Rippl method, simulation method, Azevedo Neto method, german practical method, practical English and practical Australian. In this way, this work aims to compare the volumes calculated by the methods established in the mentioned norm, and also by the method presented by Dornelles (2012), for three brazilian capitals: Belo Horizonte, Goiânia and Porto Alegre. In general, for the practical and Rippl methods, the discrepancy between the observed values for the calculated volumes of reservoirs, varying from 4,89 m³ to 39,00 m³, to Belo Horizonte, for example, is observed. This, in fact, may confuse decision making by the designer, also stressing the limitation of such methods on the performance of RHUs in its time of use. The simulation method provided, for 15,00 m³, the efficiency of 80,87%, 80,81% and 98,37% for Belo Horizonte, Goiânia and Porto Alegre, respectively. Already using the method proposed by Dornelles, in Belo Horizonte, the same volume will experience the efficiency of 87,80%; to Goiânia the efficiency of 87,00% and; in the same way for Porto Alegre, 99,70%. Comparing the last two methods, it is noticed that there is not much difference, and can be used safely. Thus, the simulation and Dornelles (2012) methods provided safer values providing data for analysis of RHUs performance indices over the years.