Restoring natural flow regimes: the importance of multiple scales

Abstract

Urbanisation changes flow regimes which negatively impact the ecology, water quality and geomorphology of receiving waters. These flow regimes need to be restored to more natural levels to improve stream health. We measured the performance of precinct scale (infiltration basin) and household scale (water tanks) stormwater retention systems against flow objectives developed from a nearby reference stream. Continuous flow data was used to determine their performance in restoring total volume, frequency, duration and magnitude of high flow events and baseflows. The different systems varied in their ability to meet flow objectives; the infiltration system was able to restore baseflows through filtration, exfiltration and attenuation, while other metrics were reduced but not to predeveloped levels. The tanks reduced runoff volume and event frequency. The individual systems studied could not meet all flow objectives, demonstrating the need for a combination of systems at different scales. We conclude that certain aspects of the flow regime are easier to restore than others and that working at multiple scales is required and that in residential urban areas, the performance of stormwater harvesting systems is limited by demand, while information system performance is commonly limited by space.

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