A report card looking at the health of the Derwent has found that investments to improve water quality are paying off, but that a broader scope may be needed to sustain river health in the longer term.
The 2011 Report Card summarises monitoring data collected by the Derwent Estuary Program (DEP) and partners in the area between New Norfolk and the Iron Pot Light. DEP Director Christine Coughanowr said the report provides a watching brief on the State of the Derwent estuary.
“As in previous years, this includes trends in sewage, industrial and stormwater pollution, monitoring results for swimming beaches and heavy metals in seafood, as well as actions taken to clean-up the Derwent,” Christine said.
“This year’s Report Card also provides a more holistic understanding of the ecological systems and processes that underpin the health of the estuary, including detailed surveys of wetlands, seagrasses and rocky reef habitats and new scientific studies of heavy metal and nutrient processes.”
“Much of this work was carried out in collaboration with the DEP’s research partners and supported through Australian Government grants.”
Ms Coughanowr said a major study of heavy metals and nutrients highlights the need to manage the estuary within a broader context that also includes the River Derwent catchment and D’Entrecasteaux Channel areas.
Releasing the 2011 report today, Ms Coughanowr said industrial discharges into the Derwent continue to fall.
“Annual discharges of organic matter from the Norske Skog paper mill have fallen by over 90 percent, while at Nystar over 120 tonnes/year of zinc and other heavy metals are being extracted from contaminated groundwater, which previously entered the Derwent,” Ms Coughanowr said.
Each summer, recreational water quality is monitored at beaches and bays around the estuary. The 2011 Report Card also shows that nine of the Derwent’s 18 swimming sites are currently classified as having good water quality; seven are fair and two are poor.
The best water quality was measured at New Norfolk Esplanade, Little Sandy Bay Beach, Hinsby Beach, Taroona, Kingston (middle), Blackmans Bay, Little Howrah and Opossum Bay.
Windermere Beach and the western end of Nutgrove Beach received poor water quality ratings. Ms Coughanowr said investigations are planned to identify and address pollution sources at these sites.
Other 2011 Report Card highlights include • Seafood safety - oysters and mussels from the Derwent estuary- including Ralphs Bay - contain high levels of heavy metals, particularly zinc, lead and cadmium. The latest DEP survey results also confirmed some fish species from the Derwent estuary have elevated levels of mercury, particularly black bream. More information can be found in the recently updated brochure ‘Should I eat Shellfish and Fish from the Derwent?’ at www.derwentestuary.org.au; • More than 15 new stormwater projects have been completed to capture litter, sediment and other pollutants; • Weed management has continued to eradicate rice grass, while the introduced New Zealand weed ‘karamu’ has emerged as a new challenge.
The Derwent Estuary Program (DEP) is a regional partnership between the Tasmanian State Government, councils, businesses, scientists and community-based groups to restore and promote the Derwent estuary.
For a full copy of the 2011 State of the Derwent Report Card, go to www.derwentestuary.org.au or pick up a copy at Council or Service Tasmania offices.