A catchment-scale experiment on stream restoration through dispersed upland stormwater retention
To date, no examples of improved ecological condition in stream ecosystems resulting from low impact urban stormwater management have been reported. We worked with a catchment community and municipality to retrofit the stormwater drainage of a 2.5 km2 urban watershed in the headwaters of a small, degraded stream to the east of Melbourne, Australia. Flow, water chemistry, algal and macroinvertebrate assemblages, and leaf decomposition were monitored in 3 tributaries and the main stem of the stream and in 3 control and 3 reference streams for 4–13 years to date. Installation of 280 stormwater systems retaining, harvesting, infiltrating and treating runoff from impervious areas of 102–104 m2 took 4 years to the end of 2013. At the time of writing, no biological changes attributable to the works have been detected, but the tributary with the most complete retention of urban stormwater runoff shows trends suggestive of increased baseflow, reduced nutrient concentrations, and unexpectedly increased electrical conductivity. With different degrees of catchment intervention among tributaries, this study will allow important inferences on the intervention extent and intensity required to improve in-stream ecological condition.
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