Secchi Page






Secchi Disk monitoring files

If you want an electronic copy of the monitoring manual or data sheet these can be accessed from the files below:

Secchi Disk manualFOGSV_2017v4_780KB



Secchi Disk Monitoring videos

We now have a promotional film and detailed instructional video on Youtube. You can access these films here:



Facebook page

We now have a Facebook page specifically for the Secchi Disk project for volunteers and supporters to share photos, tips and video from their monitoring activities.








Interesting trends

Volunteers have been recording Secchi Depths around the Gulf for over 2 years and some interesting readings have emerged.

Secchi Depths around the Gulf have ranged from a very low 70cm at Henley Beach up to 730cm at Port Noarlunga where waters are generally less turbid.

It is suggested by some that a Secchi Depth of 1.2 or less is unsafe for swimming. In the two years of data collection, 8 readings have fallen below that level at sites around the Gulf.

As yet there is not enough data to say whether there are any trends, but many sites seem to be showing an increase in turbidity rather than a decline. Although there is not enough data to say this with confidence. An example of readings is shown from Brighton.









The more data we can collect, the more rigorous it will be and the more information we can provide to decision makers and the community.


Measuring water quality – the Secchi Project

The Secchi disk used to measure water

People who observe our coastal waters regularly can’t help but notice when they are dirty.

In most cases it is possible to make a good guess as to why. Near Adelaide, stormwater is a likely culprit, and we have become accustomed to seeing murky water after rainy and windy conditions. Other causes may include dredging operations, runoff from building sites or agricultural land, waste spills etc.

The Adelaide Coastal Waters Study highlighted the importance of clean water for a healthy marine environment, particularly in relation to seagrasses, which play such a pivotal role in the gulf.

The Secchi disk disappears from view
quickly in turbid water

The Friends of Gulf St Vincent, in collaboration with the Adelaide and Mount Lofty NRM Board, have a project up and running to monitor water quality using Secchi discs. The Secchi disc is a relatively simple and inexpensive way to measure water clarity – the black and white disc is lowered into the water until it is no longer visible. This distance is the Secchi depth.

The rule of thumb is that if you can’t see your feet when you are standing in chest-deep water it is not safe to go swimming.

Similar projects have been run elsewhere – in locations where local pollution of lakes and bays was causing concern, and the benefits are that people become involved in regular observation of changes in the water quality, the data provides a baseline and record of trends, and we all learn more about the sources and impacts of pollution.

In Gulf St Vincent the Secchi depth is usually between 2 and 10 metres, but in other parts of the world measurements of 40 – 80 metres have been recorded!

The waters extending from Outer Harbour to Port Stanvac are particularly at risk from turbidity (muddy waters), but we also need to monitor coastal waters at all jetties around the gulf, so that we can identify marine areas that may be affected by turbidity now, and those which may be at risk in the future.

The project has been running since April 2012, and we are getting data for the Adelaide metropolitan jetties, but we would also really like to sign up some Secchi volunteers for the Yorke Peninsula side of the gulf.

The FoGSV will provide a Secchi kit and training to volunteers for this important monitoring program of Gulf coastal waters. The goal is to get one or more people collecting data (taking measurements and then submitting it via the Secchi Project website) from their local jetties or boats. Volunteers need to have safe access to a relatively deep measuring location. Secchi readings should ideally be taken regularly (once a week would be great) but all data collected will be useful!

If you are interested in participating in this project, or if you know of someone who might be, please contact Mel Rees at