Middle Harbour Creek

Our water quality monitoring program has shown Middle Harbour Creek to have good water quality. Find out more about the estuary and its unique features.

Middle Harbour Creek is situated in the Sydney Metropolitan region of New South Wales. It is classed as a drowned valley estuary and flows into Port Jackson/Sydney Harbour.

The creek flows through a wooded valley flanked by Sydney’s North Shore suburbs. The estuary and its surrounds are a popular recreational place for activities such as birdwatching, walking, picnicking, boating, fishing, and kayaking.

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 located between Taree and Wollongong every 3 years. The most recent sampling in the Middle Harbour Creek was completed over the 2019–20 summer when 2 sites were sampled on a monthly basis.

Middle Harbour Creek 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 'fair' and water clarity is rated 'good' giving an overall rating of 'good' or 'B'.

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 good with:

  • algae abundance graded fair (C)
  • water clarity graded good (B)
  • overall estuary health graded good (B).

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.

We have monitored water quality in Middle Harbour Creek since 2010. This table shows the water quality grades for this estuary over that time.

Middle Harbour Creek historic water quality grades from 2010-11 for algae and water clarity. Colour-coded ratings (red, orange, yellow, light green and dark green represent very poor (E), poor (D), fair (C), good (B) and excellent (A), respectively).

Grades for algae, water clarity and overall are represented as:

  • A – excellent
  • B – good
  • C – fair
  • D – poor
  • E – very poor.

As part of our Beachwatch program we assess swimming suitability at 7 swimming sites in Middle Harbour Creek using microbial indicators. We collect samples at each site weekly between October and April, and monthly from May to September, to calculate the suitability grade. Sampling is ongoing. Each grade reflects the most recent 100 water quality results to April 2022. Find out more about how we monitor beach water quality.

Local government area Swim site name Grade
Northern Beaches Clontarf Pool Good
Gurney Crescent Baths Fair
Davidson Reserve Poor
Willoughby Northbridge Baths Poor
Mosman Chinamans Beach Good
Edwards Beach Good
Balmoral Baths Good

Estuarine, lake and lagoon water can sometimes be unsuitable for swimming, especially after rainfall when stormwater and wastewater can overflow into swimming areas. Learn more about what the grades mean and how we grade swimming sites on our beach classification webpage.

Physical characteristics

Estuary type: Drowned valley

Latitude (ºS) –33.82
Longitude (ºE) 151.26
Catchment area (km2) 77
Estuary area (km2) 6.1
Estuary volume (ML) 81,900
Average depth (m) 13.4
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

Most of the land within Middle Harbour Creek catchment is occupied by urban development associated with the northern suburbs of Sydney. Around one third of the catchment remains forested, a lot of which is protected as part of Garigal National Park. Much of the riparian zone remains intact in the middle and upper reaches of the estuary.

National and marine parks

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

Community involvement

  • Greater Sydney Landcare Network is a community organisation that supports individuals and groups that work to protect, restore and improve the natural environment of Greater Sydney, which includes metropolitan Sydney, greater western Sydney, the Central Coast and Blue Mountains.
Middle Harbour Creek