Explicit scheme approach for calculating rainwater harvesting: proposed model and practical application

Urban areas face growing challenges related to stormwater management due to increasing impermeability and extreme rainfall events. An explicit methodology for the hydraulic design and sizing of rainwater harvesting systems, contributing to more sustainable urban drainage strategies. The method introduces a new routing approach in reservoirs, derived from Bernoulli’s equation and mass conservation principles, and utilizes a binomial approximation for simplification. A practical case study demonstrates the model’s effectiveness, reducing inflow peak rates by approximately 83% for a return period defined by local regulations. Sensitivity analyses were conducted to evaluate the impact of key design variables, such as pipe diameter, discharge length, and reservoir surface area. The model was experimentally validated using a reservoir with a maximum surface area of 29.12 m2, outperforming the conventional water level pool method in predicting the outflow hydrograph. The approach offers a replicable and computationally efficient tool for engineers and urban water system designers.