Barriers to Modeling the Hydrological Impact of Rainwater Harvesting in Urban Catchments

Abstract

The increasing adoption of domestic rainwater harvesting (RWH) as a supplementary/alternative water source has created changes in the hydrology of many urban catchments. To achieve sustainable urban water management, there is a need to understand and assess the impact of these changes using appropriate hydrologic estimation processes. This study investigates current hydrologic modeling procedures, including the design storm and continuous simulation approaches, to determine whether these procedures are suitable for the stated purpose. This investigation reveals that these methods are insufficient to provide a holistic assessment if adopted independently. Existing differences within the design philosophies of these current methods prevent them from being combined, so hydrologic analysis tools capable of overcoming this incompatibility are required. A case study was undertaken to test the usability of the annual exceedance probability neutral, dual probability, and synthetic runoff frequency analysis approaches to gauge hydrological impact. The use of empirical data is also examined. The analysis revealed that different combinations of these methods are suitable to assess holistically the impacts of domestic RWH depending upon local site conditions.