How much to divert? A multi-model analysis of first flush optimisation in rainwater harvesting systems

This study examines the impact of first flush diversion on rainwater harvesting system performance. It uses first-flush diversion criteria based on rainfall history, minimum rainfall depth, and various first-flush volumes reported in the literature. Three models are developed for runoff generation, potential savings, and economic aspects under various first-flush conditions. Generalizability is enhanced by considering different rainfall regions and multiple demand points. Findings indicate that the most effective criterion is first-flush diversion based on rainfall history. The study offers meaningful implications for rainwater harvesting system practitioners for designing an effective system.