Lake Illawarra

Physical characteristics

Latitude (ºS)-34.54
Longitude (ºE)150.88
Catchment area (km2)1238.4
Estuary area (km2)1,235.8
Estuary volume (ML)374275.1
Average depth (m)42.1
Roy et al. (2001) classification5III/5/B
Entrance condition6O/T
  1. Derived from DECCW (2010) NSW estuaries and coastal catchments spatial database.
  2. Includes area mapped as open water (see note 1), mangrove and saltmarsh areas (Creese R. G., Glasby T. M., West G. and Gallen C. (2009) Mapping the habitats of NSW estuaries. Industry & Investment NSW Fisheries Final Report Series 113. Port Stephens, NSW, Australia.
  3. Based on areas at 0.6 m AHD (Roper T., Creese B., Scanes P., Stephens K., Williams R., Dela-Cruz J., Coade G. and Coates B. (2011) Assessing the condition of estuaries and coastal lake ecosystems in NSW. Office of Environment and Heritage, Sydney).
  4. Estimated by dividing the total volume at 0.6 m AHD by the total surface area of the estuary including mangrove areas but excluding saltmarsh (Roper et al., 2011)
  5. Estuary group: I = oceanic embayment, II = tide dominated estuary, III = wave dominated estuary, IV = intermittently closed estuary V = freshwater bodies
    Estuary type: 1 = ocean embayments, 3 = drowned valley estuary, 5 = barrier estuary, 6 = barrier lagoon, 7 = interbarrier estuary, 8 = saline coastal lagoon, 9 = small coastal creeks, 11 = brackish barrier lake. Evolution stage: A=youthful, B=intermediate, C=semi-mature, D=mature.
    (P. S. Roy, R. J. Williams, A. R. Jones, I. Yassini, P. J. Gibbs, B. Coates, R. J. West, P. R. Scanes, J. P. Hudson and S. Nichol (2001) Structure and Function of South-east Australian Estuaries. Estuarine, Coastal and Shelf Science 53, 351-384)
  6. Entrance conditions: O = open, T = trained, I = intermittent.

Tidal prism

The volume of water moving past a fixed cross section during each flood tide or ebb tide (i.e. slack water to slack water), is referred to as the tidal prism of an estuary.

The following table shows the measured tidal prism at the location specified, along with the tidal range for near the measurement site and at Sydney Harbour.

Location:     1.3km from the entrance on 10/3/08

Tide stateFlow
(106 m3
tidal range (m)
Sydney Harbour
tidal range (m)
Ebb flow2.140.661.32
Flood flow 2.70.631.32

Tidal survey

Tidal surveys measure the hydrodynamic behaviour of an estuary during a full tidal cycle. The parameters measured include velocity, water levels, salinity, temperature and pH.

The following tidal surveys have been undertaken on this estuary. A map shows the location and plots of the flows and water levels for the most comprehensive survey.

Copies of tidal survey reports are available from the Estuary Management Program

DateData collectedFigureReport
Jan 1974Current metering at Windang Bridge and six tideboards - full cycle but continual ebb due to high lake level.-MHL366
May 1974Current metering at Windang Bridge - same as 14-15/1 but lake level lower (full ebb and flood).-MHL366
Feb 1994Current metering over a neap tide at the entrance using ADCP, water samples collected at the metering line.-AWACS 94/10
Mar 1994Current metering over a spring tide at the entrance using ADCP, water samples collected at the metering line.-AWACS 94/10
Feb 2008 to Feb 2009Extensive data collection: water levels at eleven sites; velocities at one site; and water quality profiles at twelve sites.1988-40.pdfMHL1826

Hydrographic survey

The hydrographic survey provides the depth and physical characteristics of the estuary.

The metadata associated with the survey can be found on the map sheets provided.

Map sheet number DescriptionScale    Size
53525SH1.pdfLake Illawarra entrance1:1000340.5kb
53525SH2.pdfLake Illawarra entrance1:1000327.6kb
53525.txtLake Illawarra entrance xyz dataN/A43.0kb
56207s01.pdfIndex plan, legends, notes, tidal planes & datum diagram1:15000584.7kb
56207s02.pdfLake Illawarra & Griffins Bay1:5000723.5kb
56207s03.pdfLake Illawarra, Tuggerah Bay & Koonawarra Bay Cross section locations - Mullet Creek, Hooka Creek & Brooks Creek 1:5000732.8kb
56207s04.pdfLake Illawarra, Koonawarra Bay & Yallah Bay Cross section locations - Duck Creek 1:5000609.3kb
56207s05.pdfLake Illawarra, Haywards Bay & Koona Bay Cross section locations - Macquarie Rivulet, Albion Creek & Horsley Inlet1:5000633.2kb
56207s06.pdfLake Illawarra & entrance channel1:5000734.0kb
56207s07.pdfLake Illawarra entrance channel (Bevans Island)1:2000444.7kb
56207s08.pdfLake Illawarra entrance1:2000558.7kb
56207s09.pdfLake Illawarra & Whyjuck Bay1:2000269.0kb
56207s10.pdfCross sections - Macquarie Rivulet1:1000 H 1:200 V349.6kb
56207s11.pdfCross sections - Horsley Inlet & unnamed creek1:1000 H 1:200 V237.9kb
56207s12.pdfCross sections - Hooka Creek, Brooks Creek & Albion Creek1:1000 H 1:200 V290.4kb
56207s13.pdfCross sections - Mullet Creek1:1000 H 1:200 V333.0kb
56207s14.pdfCross sections - Mullet Creek1:1000 H 1:200 V306.7kb
56207s15.pdfCross sections - Duck Creek & unnamed creeks1:1000 H 1:200 V315.6kb
56207.txtLake Illawarra xyz dataN/A632.4kb
Page last updated: 26 April 2012