Stormwater Harvesting (SWH) to alleviate water scarcity is often hindered by the lack of suitable available storage in urban areas. This research aimed to discover an economically viable strategy of storing runoff in existing stormwater ponds with the assistance of rudimentary Real Time Control (RTC) techniques to increase the effective storage capacity. The Diep River sub-catchment situated in the southern suburbs of Cape Town, South Africa, that has several stormwater ponds that were largely constructed for the purposes of flood mitigation, was used as a case study. Six SWH scenarios utilising three distinct RTC strategies coupled with two alternative water demand alternatives were simulated with the aid of 10 years' of historical rainfall data with a view to determining the unit cost of supplying selected developments with non-potable water. The use of RTC to increase the effective storage of the ponds was shown to improve the volumetric yield without significantly impairing the flood mitigation provided by the system at a cost that was comparable to what the local residents were already paying for potable water. This finding is important as it suggests a cost-effective way of overcoming one of the greatest limitations associated with stormwater harvesting.