Assessing the performance of multi-nodal rainwater management systems

Rainwater Management Systems (RMS) is a term that describes the decentralisation and management of rainfall at source for multiple purposes. Many studies have focused on the water saving potential of RMS at a small single storage single demand (S-D) scale, but research into the stormwater management potential of a multi-nodal network scale is lacking. Multi-nodal rainwater management systems comprise numerous storage and demand nodes (nSnD) and are hypothesised to be a more effective way of improving water supply and stormwater management performance of RMS in a domestic network.

This MPhil evaluates the performance of multi-nodal RMS for the water supply and stormwater management potential compared to a conventional S-D system. To achieve this, S-D and nSnD models were created and performance metrics have been developed to enable comparison analysis for the water supply and stormwater management potential. The five identified metrics are water supply efficiency, water supply frequency, stormwater retention efficiency, peak outflow and time above greenfield runoff rate. The feasibility comparison of the model showed that the model was capable of simulating results comparable to monitored RMS data and that the performance metrics developed efficiently analysed RMS performance. The model sensitivity analysis explored the effects of behavioural model, time step and the demand profile on model accuracy. The findings of the sensitivity analysis highlighted that time-step had a high impact upon accuracy, whilst behavioural model and demand profile had a reduced impact on the accuracy.

The nSnD to S-D comparison has shown that the stormwater management and water supply potential of a RMS can both be enhanced through the introduction of a multi-nodal network. nSnD systems are capable of producing a reduced peak outflow, reduction to the time outflow exceeds greenfield runoff rate and an increased water supply efficiency, water supply frequency and stormwater retention efficiency when compared to that of an S-D system.