Crooked River is classed as a barrier river with an entrance that is intermittently open and closed to the ocean.
We sample a subset of the estuaries between Wollongong and the Victorian border every 3 years. The most recent sampling in the Crooked River was completed over the 2023–24 summer, when 2 sites were sampled on a monthly basis.
Water quality report card
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.
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 numerical scores for these 2 indicators are averaged to give the overall grade.
Algae
Water clarity
Overall grade
The report card shows the condition of the estuary was fair with:
- algae abundance graded fair (C)
- water clarity graded good (B)
- overall estuary health graded fair (C).
Grades for algae, water clarity and overall are represented as:
- A – excellent
- B – good
- C – fair
- D – poor
- E – very poor.
Go to estuary report cards to find out what each grade means, read our sampling, data analysis and reporting protocols, and find out how we calculate these grades.
We have monitored water quality in the Crooked River since 2008. This table shows the water quality grades for this estuary over that time.
| Year | Algae | Water clarity | Overall grade |
|---|---|---|---|
| 2023–24 | C | B | C |
| 2022–23 | B | B | B |
| 2020–21 | B | B | B |
| 2017–18 | B | B | B |
| 2014–15 | C | C | C |
| 2008–09 | B | C | C |
Physical characteristics
| Estuary type | Barrier river |
|---|---|
| Latitude | –34.77 (ºS) |
| Longitude | 150.82 (ºE) |
| Catchment area | 32 km2 |
| Estuary area | 0.3 km2 |
| Estuary volume | 140.8 ML |
| Average depth | 0.5 m |
Notes: km2 = square kilometres; m = 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 Crooked River is highly disturbed, with about 75% of land used for grazing and rural residence. Urban land use makes up less than 10% of the catchment at Gerroa and Seven Mile Beach, including 2 holiday parks. A water recycling plant is also located at Gerroa. Over 10% of the catchment is forested and this includes some of Seven Mile Beach National Park.
National and marine parks
- The largest conservation area in the Crooked River catchment is Seven Mile Beach National Park.
- There is no marine park associated with the Crooked River estuary.
Community involvement
- Landcare Illawarra support volunteer groups working to improve the environment in this region.
Aerial view of Crooked Creek
Local government management
Local councils manage estuaries within their area. Where an estuary is attached to a marine park, marine park management teams are responsible for ensuring compliance with marine park zoning.
Kiama Municipal Council manages the Crooked River estuary.
Threatened species
An endangered greater glider population lives in the southern part of the Crooked River estuary catchment.
Read more about the biodiversity in our estuaries.