St Georges Basin

Our water quality monitoring program has shown St Georges Basin to have excellent water quality. Find out more about the estuary and its unique features.

St Georges Basin is located on the south coast of New South Wales near Jervis Bay. It is classed as a lake which is permanently connected to the sea via a narrow channel adjacent to the township of Sussex Inlet.

The main tributaries to St Georges Basin are the Wandandian and Tomerong creeks. Several towns surround this large waterbody, which is a popular fishing spot.

Estuary health and features

Water quality

As part of our water quality monitoring program we assess the water quality and ecosystem health of an estuary using a range of relevant indicators. We sample a subset of the estuaries between Wollongong and the Victorian border every 3 years. The most recent sampling in St Georges Basin was completed over the 2008–09 summer when 2 sites were sampled on a monthly basis.

St Georges Basin water quality report card for algae and water clarity showing colour-coded ratings (red, orange, yellow, light green and dark green, which represent very poor, poor, fair, good and excellent, respectively). Algae is rated 'excellent' and water clarity is rated 'excellent' giving an overall rating of 'excellent' or 'A'.

This report card represents 2 water quality indicators that we routinely measure: the amount of algae present and water clarity. Low levels of these 2 indicators equate with good water quality.

The report card shows the condition of the estuary was excellent with:

  • algae abundance graded excellent (A)
  • water clarity graded excellent (A)
  • overall estuary health graded excellent (A).

Find out more about our estuary report cards and what each grade means. Read our sampling, data analysis and reporting protocols and find out how we calculate these grades.

Physical characteristics

Estuary type: Lake

Entrance
location 		Latitude (ºS) –35.19
Longitude (ºE) 150.59
Catchment area (km2) 315.8
Estuary area (km2) 40.9
Estuary volume (ML) 215,078.9
Average depth (m) 5.3

Tidal exchange volume

Tidal exchange volume or tidal prism data is available for this estuary. This tidal prism was measured in 2001. 

Tide state Flow
(106 m3)		 Local tidal
range (m)		 Sydney Harbour
tidal range (m)
Ebb flow 0.39 0.54 1.22
Flood flow 0.3 0.49 1.24
Notes: km2 = square kilometres; m = metres; m3 = cubic metres; ML = megalitres.

Water depth and survey data

Bathymetric and coastal topography data for this estuary are available in our data portal.

Land use

The catchment of St Georges Basin has relatively low disturbance with over 70% forested areas, including part of Morton National Park. Urban areas make up almost 10% of the catchment and include the townships of St Georges Basin, Sanctuary Point and Sussex Inlet. Cleared land for grazing accounts for less than 10% of land use.

Web cam

The Sussex Inlet bar crossing web camera provides real-time video of conditions within the river entrance immediately offshore to help with bar crossings and boat safety.

National and marine parks

  • Morton National Park is the largest conservation area within this catchment.
  • This estuary does not flow into a marine park.

Citizen science projects

  • The Budawang Coast Nature Map is an online data platform the community can use to record and identify biodiversity. Data collected is used to map the distribution of native plant and animal species from Moruya up almost to Kiama.

Community involvement

  • The Shoalhaven Landcare Association represents a range of volunteer groups working in and around this catchment.
  • South East Landcare is an umbrella organisation that represents a network of Landcare associations including those in the Shoalhaven area.
St Georges Basin

Local government management

Local councils manage estuaries within their area unless the estuary is attached to a marine park. Shoalhaven City Council manage this estuary.