Alternative water sources as a pragmatic approach to improving water security

This study considered a volumetric water balance to assess the influence of AWS on future water security in the City of Johannesburg. Hydrological modelling was implemented in HEC-HMS to quantify runoff volumes up to the year 2050, whilst a GIS-based MCDA was run to cater for socio-economic factors influencing RWH. The outputs from these analyses, together with city water balance, were integrated into WEAP to develop a decision support tool to evaluate the potential of AWS to improve water security. The RWH suitability map shows that at least 50% of the city meet the potential for RWH, whilst the hydrological simulation shows that the harvestable runoff is twice the total non-potable water requirement, demonstrating that RWH reliability can be significantly maximised with increased storage. The scenario analysis highlights that AWS can bridge the gap between water supply and demand, thereby building resilience to climate uncertainties and protecting the environment.