1.0 INTRODUCTION The Derwent estuary lies at the heart of the Hobart • Derwent Valley Council metropolitan area and is an asset of great natural beauty • Glenorchy City Council and diversity (Figure 1.1). It is an integral part of Tasmania’s • Hobart City Council cultural, economic and natural heritage. The estuary is • Kingborough Council an important and productive ecosystem and was once a • Southern Water major breeding ground for the southern right whale. Areas • Norske Skog Boyer of wetlands, underwater grasses, tidal flats and rocky reefs • Nyrstar Hobart support a wide range of species, including black swans, • Tasmanian Ports Corporation wading birds, penguins, dolphins, platypus and seadragons, • Hydro Tasmania as well as the endangered spotted handfish. • Australian Government • Tasmanian Aquaculture and Fisheries Institute/ Approximately 200,000 people – 40% of Tasmania’s University of Tasmania population – live around the estuary’s margins. The • CSIRO Marine Research Derwent is widely used for recreation, boating, fishing and • NRM South marine transportation, and is internationally known as the • Tasmanian Conservation Trust finish-line for the Sydney Hobart Yacht Race. The Derwent supports several large industries, including paper and zinc production, boat-building and chocolate manufacturing. Despite the pressures it faces on a daily basis, the Upstream, the Derwent supplies most of Hobart’s drinking Derwent is showing promising signs of recovery in water and is an important source of hydro-electric power. response to management actions undertaken by councils and industries. As the condition of the estuary improves, A number of environmental issues affect the there is growing interest in conserving and enjoying the Derwent estuary: Derwent’s natural features. • heavy metal contamination of water, sediments and seafood; The DEP is underpinned by a comprehensive integrated • loss of estuarine habitat and species; monitoring program that documents environmental • introduced marine pests and weeds; conditions and trends, and also supports scientific • altered river flow regimes and blocked fish migration research into key issues such as heavy metals and nutrient routes; processes. Cooperative monitoring arrangements between • elevated levels of nutrients and organic matter, the State Government, industries, local governments and and low dissolved oxygen levels. the scientific community have generated a wealth of new information on water and sediment quality, seafood safety Sources of contaminants to the Derwent include sewage, stormwater and industrial wastes, as well as and estuarine habitats and species, which have been agricultural, forestry and aquaculture inputs from the analysed and interpreted in this new report. adjacent Derwent and Jordan River catchments and D’Entrecasteaux Channel. Although there have been major Several large integrated projects have also been improvements in recent years, the Derwent remains a completed during the past five years, in particular significantly modified estuary. A strategic and coordinated Water Quality Improvement Plans for heavy metals and management approach across all levels of government, nutrients, supported by the Australian Government. industry and the community remains our best prospect for These projects included the development of estuarine a cleaner and healthier estuary in the future. hydrodynamic, sediment transport, toxicant and nutrient response models which have both improved The Derwent Estuary Program (DEP) is a regional our understanding of estuarine processes and provide partnership between the Tasmanian Government, local a good basis for predictive modelling of different governments, industry, scientists and the community management scenarios. to restore and promote our estuary. The DEP was established in 1999 and has been nationally recognised The new State of the Derwent Estuary report reviews for excellence in reducing water pollution, conserving habitats and species, monitoring river health and environmental quality data collected since 2003 to give a promoting greater use and enjoyment of the foreshore. representation of current estuary health and to highlight environmental trends. Sections 2 and 3 review Derwent The DEP’s partners and supporters include: estuary values and uses and provide an overview of the • Tasmanian State Government estuary’s physical setting. Section 4 reviews pollutants • Brighton Council associated with point and diffuse sources and documents • Clarence City Council trends over the past six years. Section 5 provides an State of the Derwent Estuary 2009 13 overview of several integrated studies, carried out in Section 11 provides an update on introduced species and recent years. Sections 6 through 8 give more detailed Section 12 reviews recent initiatives related to climate information about water quality, sediment quality, and change. Finally, Section 13 contains a summary and seafood safety. Section 9 reviews the latest information recommendations and Section 14 provides an up-to-date on Derwent habitat and species. Section 10 reviews list of references. several key foreshore issues and opportunities, Figure 1.1: Derwent estuary SOUTHERN LOCATION MIDLANDS SOUTHERN MIDLANDS Brighton River BRIGHTON N Bridgewater SCALE 0 5 River Derwent Conservation Area kilometres Jordan Green Bridgewater Island Causeway Herdsmans Green Point -URPHYS Cove Nature Reserve M E E H A N R A N G E &LAT Goulds Boyer UPPER Lagoon ESTUARY Norske Skog New Paper Mill SORELL Norfolk $OGSHEAR Windemere 0T Bay MIDDLE ESTUARY Bowen Bridge DERWENT Elwick Risdon VALLEY Bay Cove East Risdon CLARENCE Prince of Wales GLENORCHY Bay Nature Reserve (CITY) (CITY) GLENORCHY Nyrstar Hobart Smelter GeilstonBay New Town Lindisfarne Bay Cornelian Bay Bay Lindisfarne Tasman Bridge HOBART Bellerive MT Battery Point KangarooBay Howrah WELLINGTON Sullivans HOBART Cove Tranmere (CITY) Sandy Bay Rokeby Lauderdale Nutgrove Racecourse Flats Lauderdale Browns Taroona $ROUGHTY0T RALPHS BAY LOWER ESTUARY DERWENT River Alum Mary Ann #LIFFS Bay KINGBOROUGH Kingston Mortimer Opossum SOUTH ARM Bay HUON Bay Blackmans VALLEY Bay Program Area RIVER Half Boundary Moon Bay Local Government Area Boundary South Arm Seacroft NORTH HOBART Local Government Bay Tinderbox #APE$IRECTION (CITY) Area Name WEST s)RON0OT Tinderbox BAY Marine Bruny Reserve Island STORM BAY 14 State of the Derwent Estuary 2009.