The feasibility of rainwater and stormwater harvesting within a winter rainfall climate context: a commercial building focus

Abstract

Cape Town, South Africa, falls within a winter rainfall region, making it difficult to assess the feasibility of rain- and stormwater harvesting. The reason for this is because the region’s high water demand period coincides with the low rainfall summer season, thereby limiting the availability of this alternative water resource when most needed. During this study, rainwater harvesting for toilet flushing purposes, collected from roof surfaces, was practically assessed by means of inserted flow meters at a pilot study site in Kommetjie, Cape Town. The combined and single system roof- and land surface runoff yields and savings of commercial buildings within the Kommetjie business area, were also theoretically assessed by making use of a mathematical roof- and land surface runoff model specifically developed during this study. The statistical testing of the hypotheses statements relating to the pre- and post-harvesting savings at the pilot study building, compared against the average actual municipal water usage, were performed. Hypotheses testing were also performed in order to compare the theoretical rain- and stormwater runoff yields for the commercial business area against the average actual municipal water consumption. The conclusions drawn from this study indicated that valuable potable water, as well as related financial savings, can be achieved within a winter rainfall region, thereby making rain- and stormwater harvesting a feasible option for commercial businesses in Cape Town.