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Estuaries of NSW

What is an estuary?

Estuaries are places of transition. They are where freshwater draining from our coastal catchments mixes with ocean waters. Broadly speaking, estuaries are semi-enclosed waterbodies with open or intermittently open connections with the ocean.

Estuaries in NSW vary in their shape and size, ranging from large coastal embayments and drowned river valleys, such as Port Stephens and the Hawkesbury River, to coastal lakes, such as Lake Macquarie and Wallis Lake, and smaller intermittently open coastal lakes and lagoons, such as Manly Lagoon and Tabourie Lake. Estuaries also support many different habitat types and species.

Estuaries provide many services and are relied on for commercial and cultural activities, tourism and recreation. The way we use estuaries can affect how they function and their overall condition or health.

Estuaries are subject to pressures from human activities as well as natural events such as storms and floods. Common threats to estuary health include increased nutrients and eutrophication, loss of habitat and biodiversity, contaminants and pollutants, accelerated rates of sedimentation, disturbance of acid sulfate soils, changes to freshwater and tidal flows, invasive species and climate change.

The overall target for managing NSW estuaries is that by 2015 there is an improvement in the condition of estuaries and coastal lake ecosystems (NSW State Plan, 2010). 

Information about estuaries

Through the Estuary Management Program, the Office of Environment and Heritage (OEH) collects data and provides guidance to assist in the management of estuaries. Additional information available includes:

• A summary of the estuaries of NSW and some of their physical characteristics.
  
• OEH's Estuary Management Program assists local councils and communities to prepare and implement coastal zone management plans. Completed plans (completedplansoct2010.pdf; 45 KB) are available from the relevant local council.
• Water level data - On behalf of OEH, Manly Hydraulics Laboratory maintains a network of water level recorders. The location of recorders and data for these sites can be obtained through Manly Hydraulics Laboratory.
• Tidal surveys measure tidal characteristics, including tidal flow and velocity, water levels and physical water quality characteristics.
  
• Hydrographic surveys measure the depth and bottom configuration of waterbodies. 
  
• Tidal and mangrove limits - This work defines the upstream tidal limits in estuaries (the point that tides do not pass) and the upstream limit of mangroves for the main arm and tributaries of estuaries. See Survey of tidal limits and mangrove limits in NSW estuaries 1996 to 2005 (20060118DNRSurveyTidalMangroveLimits.pdf; 3.5 MB).
• The Saltwater Wetlands Rehabilitation Manual provides guidance on the rehabilitation and management of swamp forests, saltmarsh, mangroves and seagrass.
• Environmentally Friendly Seawalls: A guide to improving the environmental value of seawalls and seawall-lined foreshores in estuaries provides options for improving the environmental value of existing seawalls and creating new seawalls.

In addition to the Estuary Management Program other sources of useful estuary information include the following.

• OEH recently mapped the boundaries of estuaries in NSW and their catchments. The spatial data is available from maps.environment.nsw.gov.au.
• OEH monitors the health of NSW estuaries through the NSW Monitoring, Evaluation and Reporting Program. The Estuary Management Program can provide funding to assist local councils undertake estuary specific assessments.
• Habitat information and maps showing the distribution of seagrass, mangroves and saltmarsh within NSW estuaries is available from Department of Primary Industries.
• OzCoasts provides information about Australia's coast, including estuaries. Information includes conceptual models, fact sheets on indicators and management tools.