Judy Edwards

Judy Edwards

Former Minister for the Environment; Science

    Increasing oxygen in rivers a major priority

    23/11/2005 12:00 AM

    The State Government is taking a two-pronged approach to breathing life into the upper reaches of the Swan River.

    A portable oxygenation unit will be mobilised in 2006 as a ‘first line’ response to stressed fish in the river. This type of technology is used in the mining industry to deal with dewatering and chemical treatment.

    At the same time, the Government will be determining where best to locate a large-scale oxygenation plant in order to oxygenate a large section of the river where fish can move to during times of stress.

    The large-scale plant will build on a knowledge that has been gained through operating successfully a system in the Canning River for the past five years and which has reduced the incidence of fish deaths.

    Environment Minister Judy Edwards today said low oxygen levels in the Swan and Canning rivers were recognised in the Swan-Canning Cleanup Program Action Plan as a major cause of nutrient release from river sediments and loss of ecological function.

    “There is concern that a lack in oxygen, together with prolonged algal blooms, is resulting in fish deaths, particularly in autumn,” Dr Edwards said.

    “The scale of fish death events vary from year to year and the fact they do occur is of concern. Experience from the Canning River oxygenation program indicates that it definitely is one tactic to be explored with the aim of introducing it into the upper reaches of the Swan to prevent mass fish deaths.

    “Oxygenation into the Canning River has shown positive results with fewer fish deaths and a significant decrease in nutrients levels, a primary cause of algal blooms that are a primary cause of the deaths.

    “This work has provided a much-needed life support system for the Canning River and demonstrated the potential benefits of large-scale oxygenation in the rivers.”

    Oxygenation involves pumping low-oxygen water from the bottom of the river to a mixing plant where it is injected with oxygen and then returned to the river. The oxygenated water promotes the removal of nitrogen through chemical processes and helps break down organic materials in the sediment. This improves water quality and provides better conditions for aquatic life.

    Low levels of oxygen in the river occur frequently throughout summer and autumn. The oxygenation of the river will allow the Swan River Trust to maintain a level of satisfactory water quality throughout this period.

    Dr Edwards said the State Government had committed $250,000 to investigate the oxygenation program in the Swan River and a further $87,000 to ensure the maintenance of the oxygenation equipment currently used in the Canning River.

    Minister's office: 9220 5050