Cities as water supply catchments – Stream ecology (Project B2.1)
Urban streams are commonly degraded by stormwater that runs off hard surfaces such as roofs and roads. Built-up, impervious urban areas result in issues such as large, intense flows of stormwater through pipes and drains resulting in less water infiltrating into the ground, and decreased evaporation and baseflow leading to deteriorating water quality. However, integrated stormwater management and harvesting offers the potential to protect urban streams from this degradation, or to return ecological function to already degraded streams.
The project aims to determine the impact of integrated stormwater management strategies, including stormwater harvesting, on the hydrology and water quality of streams, and to assess the subsequent ecological and geomorphic responses.
The project provided an informed and confident basis for managing stormwater (including stormwater harvesting, along with other stormwater retention, treatment and infiltration- based technologies) with the goal of improving the health of aquatic ecosystems of existing urban areas, and protect those of greenfield developments.
The project tested and demonstrated its hypotheses and conceptual frameworks through demonstration projects, with the primary vehicle being the Little Stringybark project (www.urbanstreams.net/lsc/). This is the first study to monitor an entire catchment (in this case of 450 ha) before and after the introduction of stormwater harvesting, in order to measure the combined hydrological and ecological response.
Researchers developed indicators such as runoff frequency or rainfall retention capacity used them to assess the impact of stormwater harvesting on the hydrology and water quality of streams.
The outcomes of this project will give confidence to waterway managers that they can apply stormwater harvesting as part of a strategy to improve the condition of urban waterways.