Assessing the Potential for Potable Water Savings in the Residential Sector of a City: A Case Study of Joinville City

Abstract

The objective of this study is to evaluate the potential for potable water savings by using rainwater in the residential sector of Joinville, a city located in southern Brazil. Data on roof areas of residential buildings were obtained from the Joinville city council. By considering the roof areas and typologies of residential buildings, representative models were created. The following parameters were used to determine the rainwater tank capacity: the number of dwellers; the total daily water demand per capita; and the rainwater demand. To carry out the simulations for determining the optimal rainwater tank sizes and potential for potable water savings, the computer program Netuno was used to run 33,720 different scenarios. By considering the occurrence percentage for each representative building model (weighted average), the average potential for potable water savings by using rainwater was calculated. The average potential in the central region of Joinville was 18.5% when there is rainwater use only in toilets, and 40.8% when there is rainwater use in toilets and washing machines. The rainwater harvesting system showed a better performance for a rainwater demand equal to 20% of the total daily water demand. The results indicate the necessity to properly size rainwater tank capacities to meet water demands, thereby encouraging more people to adopt rainwater harvesting as an alternative source for non-potable water in buildings. The demand for rainwater should be carefully evaluated, especially in multi-story residential buildings, due to the low availability of roof areas.

Urban FEW Nexus Model for the Otun River Watershed

“…From all the strategies, the authors indicated that water-efficient fixtures were the best water reduction strategy, contributing 59% of the total water reduction. Custódio and Ghisi (2019) reported that the potential water savings were 18.5% when rainwater was used in toilets and 40.8% when rainwater was used in toilets and washing machines in Joinville (Brazil). Due to the sizable water savings that can be reached by implementing different conservation practices, the ORW and especially the Pereira/Dosquebradas urban area will benefit from implementing any of the approaches previously mentioned.…”

Stormwater Harvesting from Roof Catchments: A Review of Design, Efficiency, and Sustainability

“…For example, a rainfall amount of only 640 mm/yr has a roofing area of 2450 m 2 in the paper of Custodio and Ghisi (2019), whereas in the study of Sámano-Romero et al ( 2016), a rainfall amount of 4239 mm/yr has a roofing area of only 50 m 2 which shows that the recorded rainfall amount is usually not the basis for computing the area of the roof. However, most buildings' roof spaces are not large enough to collect enough rainwater to meet demand [53]. Nevertheless, catchment area and catchment surface type can be changed to enhance system performance [54].…”

Comprehensive Assessment Methodology for Urban Residential Rainwater Tank Implementation

“…These raintank yield values represented median value from 10,000 stochastic simulation runs. Using a similar modelling approach considering 33,720 scenarios, Custodia and Ghisi [31] reported 41% of potable water saving when rainwater is used in toilets and washing machines.…”