Climate change and rapid urbanisation have meant there is increasing pressure on water supplies in human settlements in Africa. This has led to increasingly unreliable water supplies and outages in many drought-stricken areas.

It is therefore important to understand how these pressures can be addressed and alternative sources of water found. One solution is to develop onsite rainwater harvesting systems. These capture rainwater from roofs and other surfaces and store this. This stored water can then be used instead of municipal water supplies for uses such as cleaning, irrigation and flushing toilets.

While these systems can be highly effective and significantly reduce mains water consumption, they are not widely used in Africa. This situated has been compounded by a lack of access to guides that enable the effective calculation and sizing of rainwater harvesting systems.

To address this gap this study presents and critically evaluates an alternative rainwater harvesting design methodology based on the Rainwater Use Model (RUM). The RUM methodology is compared to conventional methodologies by applying this to a case study building to carry out rainwater harvesting calculations for a range of scenarios.

Results suggest that the RUM methodology may be more accurate than conventional methods. In addition, by enabling different aspects of the systems to be tested rapidly, the RUM methodology provides useful guidance on where investments should be made in the design of a rainwater harvesting system. The study will be of interest to Architects, Engineers and Planners who need to develop more resilient and sustainable water resources in human settlements in dry areas of the world.

This is the abstract for the study which was published recently in the Sustainability Handbook 2020, published by Alive2Green.