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Research focuses on increasing the lifespan of stormwater ponds in Canberra

Canberra’s stormwater system is under the spotlight with current research from the University of Canberra taking a closer look at ways to better manage nutrient removal using retention ponds and lakes.

Presenting at the Australian Water Association ACT Water Matters Conference in June, University of Canberra Institute for Applied Ecology Research Fellow Rod Ubrihien said research is underway to help increase the lifespan of stormwater ponds in the region.

“Like a lot of cities, Canberra’s stormwater system is predominantly concrete drains. It’s not a natural system and you don't lose any contaminants,” he said.

“Canberra has many urban ponds that were established for stormwater management; they play an important role in removing contaminants and nutrients from urban stormwater.

“These ponds have a useful lifespan that is limited by the capacity of the sediment to accumulate contaminants.

“We are working closely with the ACT Government on two projects. The aim is to understand these systems better to influence policy and improve the way these systems are managed to create better outcomes for the public and environment.”

In coordination with the ACT Healthy Waterways initiative, the first study is assessing nutrient levels in Lake Tuggeranong and their relation to algae blooms.

“Lake Tuggeranong is a major man-made lake in the ACT that allows for increased water retention and to clean up the water before it goes back into the Murrumbidgee and Murray-Darling Basin,” Ubrihien said.

“Over time, the nutrient concentrations in the lake have built up and we are looking at ways to manage that. We are monitoring all the inflows to the lake and also doing regular in-lake sampling so that we can determine whether the algae blooms that regularly occur in the lake are sustained by internal nutrient loading from within the lake, or from nutrient inflows to the lake.

“In the second year, we are going to add some in-lake mesocosms and test some chemical and engineered solutions for better lake management.”

Ubrihien added that the second study involves trialling water fluctuations to assess the effect pond levels have on nutrient retention in sediments.

“The ponds have been put in as a means of slowing down the water flow, which allows for some of the contaminants to settle out and be removed from the water. But they have a lifespan,” he said.

“There is some evidence that fluctuating the water level will increase the lifespan of these ponds due to the resultant chemical and physical changes in the sediment.

“The two-year study involves fluctuating the water levels in some ponds and having some control ponds kept at full level, and monitoring the effect on water quality. We will also be checking macrophyte communities within the ponds to see if the water level fluctuation affects pond vegetation.”

Ubrihien said that while the research projects are underway, sampling water for these studies has thrown up a few challenges.

“It’s a huge project; to determine what, when and where to monitor is more complex than it might seem at face value,” he said.

“In a system that incorporates the ponds in a network of concrete drains, establishing an effective design and water sampling protocol presents many challenges.”

Ubrihien also said the ACT is currently developing significant infrastructure to manage and improve urban waterways.

“There will be a need to assess these, as well as potentially implement the recommendations from studies such as the one I am working on,” he said.

“The management of urban waterways is difficult and will continue to present challenges and opportunities.”

Register for the ACT Water Matters Conference to hear more from Rod Ubrihien about the stormwater research projects currently being carried out in the ACT. 

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