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Study improves water quality at Emigrant Creek Dam


7 December 2006
Introduced fish species and high nutrient levels have been identified as major causes of algae problems in the Emigrant Creek Dam, in a three-year study by Southern Cross University researchers.

Associate Professor Graham Jones and PhD student Darren Akhurst, from the University’s School of Environmental Science and Management, have been working with Rous Water to find solutions for the algal problems in the dam, which is a vital part of the water supply for Lennox Head and Ballina.

The study has provided a number of innovative solutions to improve water quality in the dam.

“For many years the dam has been suffering from algae problems related to high nutrient levels,” Professor Jones said.

“As the summers get hotter these algae problems have become worse, but no one had investigated in detail what was fuelling the increased algae, or how the problem could be lessened.”

Darren Ackhurst has carried out seasonal studies over two years to see how the amounts of nutrients delivered to the dam in run-off and rainfall had varied. He also looked at how the nutrients could be affected by changes in dissolved oxygen during hotter years.

“One key area highlighted by the study was the effect of introduced fish species causing elevated nutrient levels in the dam,” Professor Jones said.

“Fish like carp, bass, and gambusia have been placed in circular tanks on the dam to measure the effects of these fish at increasing nutrient levels in the water, thus fuelling further increases in algae.

“Carp are aggressive sediment feeders disturbing nutrient levels in the sediments which then increase water column algae.

“Introduced fish like Gambusia prolifically graze essential parts of the aquatic food chain. This allows algae to grow unchecked as there is reduced grazing pressure which naturally keeps algae levels low.

“When these fish are in abundance, algae levels increase in the water column because these fish reduce natural predators that keep the algae levels low. Introduced fish like Gambusia therefore interfere with the natural food chain in the water column.”

Professor Jones said the study had involved engineering input from Southern Cross University’s Dr Leigh Davison and Professor David McConchie. Darren also spent three months in the United States looking at solutions for similar water storages.

“Using a unique technology developed by Professor McConchie’s research group Darren was able to decrease nutrient levels to acceptable levels,” Professor Jones said.

“The technology employs a waste product from the aluminium industry which can remove toxic metals and nutrients from waste streams and water storages like Emigrant Creek Dam.”

Rous Water has also been working on a number of strategies to improve water quality in the dam. These include establishing the Healthy Catchments Program which provides financial assistance to landholders in the Emigrant Creek catchment to undertake environmental works that improve the health of Emigrant Creek.

Additionally, Rous Water employs a team of bush regenerators who have planted thousands of rainforest trees and plants around the foreshores of Emigrant Creek Dam. Once established these plant communities will improve native habitat, filter storm water run-off and provide shade to further reduce algal growth.

Professor Jones is the director of the Centre for Climate Change Studies, which aims to find solutions to water quality and water resource issues in the Northern Rivers as temperatures increase and the climate becomes even drier.

“During these conditions nutrient and algae problems in many of our water storages will increase. To overcome many of these problems we have to be innovative enough to try new solutions,” he said.

Photo: Craig Taylor, from Southern Cross University, with a European carp caught in Emigrant Creek Dam.

Media opportunity: Associate Professor Graham Jones, Darren Ackhurst and Robert Cawley from Rous Water will be inspecting Emigrant Creek Dam on Friday, December 8, at 9.30am.

Media contact: Brigid Veale Southern Cross University communications manager 02 66593006 or 0439 680 748.