Metrowater, Auckland City’s water utility operator, identified two stormwater sites as pilot sites which they suspected had markedly different flow and water quality characteristics.

To provide accurate flow data, AWT installed compound weirs specifically designed and calibrated for each site and purpose built electronics that were developed to trigger sampling based on the capture flow data. Trigger levels were site-specific and chosen to optimise sampling throughout first flush and subsequent peaks in flow. The system collected stormwater samples for the analysis of 20 different determinants.

It was connected to telemetry that informed AWT when sampling was underway. This ensured that samples were delivered to the laboratory for testing within 6 hours and staff were notified, enabling them to perform additional on-site analyses during storm events.

“Our system complemented Metrowater’s Integrated Catchment Programme, which together were able to demonstrate the variability of stormwater quality throughout Auckland.”

This is a cost-effective approach that allows samples to be analysed within 6 hours and enables Metrowater to make truly informed decisions.