The Estuary Watch program
The health of the Balcombe Estuary is measured monthly. See the report.
Berg Mt Martha’s Estuary Watch data can be viewed on Melbourne Water’s Estuary Watch website.
A bird’s eye view of our estuary
The water quality of a waterway is basic to its ability to support the plant and animal life within and around it. Water quality reflects the health of the whole catchment. Since the late 1990s, BERG Mt Martha has been keeping a check on the water in its section of Balcombe Creek through the national Waterwatch program.
The Waterwatch Program
The Waterwatch Program was set up by the Australian Government in 1993, and is supported by the Government’s Natural Heritage Trust. Waterwatch provides standardised methods and equipment for local groups to monitor water quality in their rivers, streams and lakes. Under Waterwatch, nearly 3000 groups across the country are monitoring water quality at over 7000 sites throughout 200 catchments.
Test results are collated in the Waterwatch Victoria database, which allows community data to be pooled, analysed and interpreted at the catchment level and beyond. The information collected provides a basis for action to tackle problems and improve waterway health.
At BERG MM, we also record the results of our testing on our own database.
For more information on Waterwatch Victoria go to www.vic.waterwatch.org.au.
Local Monitoring Sites
On the Mornington Peninsula, BERG MM is one of 11 community or friends groups that monitor 23 sites on 10 different waterways. Other sites monitored are at Coolart Wetlands, Balnarring Wetlands, Mantons Creek, Stoney Creek, Chinaman’s Creek, Warrangine Park, Sunshine Creek, Merricks Beach drainage, and Watson Creek.
Two community groups monitor Balcombe Creek at six different sites. BERG MM now monitors at Augusta Street, Uralla Road bridge and The Briars. The Mt Eliza Association for Environmental Care (MEAFEC) monitors two sites (Eramosa Road, and Mt Eliza Regional Park at Claremont Street).
BERG MM carries out its physical and chemical measurements on the fourth Sunday of every month and seasonal macro-invertibrate testing 4 times per year..
Measures of water quality
Monitoring involves six measures of water quality:
- Electrical conductivity provides a measure of salinity (dissolved salt increases water’s conductivity).
Levels measured by BERG MM at the Augusta Street testing site are well outside the “fresh water” levels set by Waterwatch. These readings are consistent with those of tidal estuaries and are very different to the up-stream values found at Uralla Road bridge and The Briars. The Waterwatch levels are probably not relevant for the Augusta Street site, which is within the creek’s tidal zone. Levels set for estuaries in other countries suggest that BERG MM’s readings are well within healthy limits.
Salinity will also vary in the estuary depending on whether or not the creek mouth is open, and how much water is flowing downstream. We still have much to learn about these variations and what actually constitutes a healthy range of readings in our creek.
- pH is a measure of acidity. Some of the influences on this in Balcombe Creek are the rock and soil characteristics of the creek bed as well as plant activity and oxygen levels. pH levels measured are within the limits that Waterwatch identifies as healthy.
- Turbidity – the cloudiness of water – is caused by suspended particles that reduce the passage of light. The particles can be soil (clay, silt, sand), algae, plankton, micro-organisms, and other substances. Major contributors include soil erosion and run-off from farm land, eroded or stock-trampled creek banks, and dirt roadways. In cloudy water, less light reaches aquatic plants, frog spawn, and other living things. Turbid water also absorbs more heat and so tends to be warmer than clear water.
Levels of turbidity measured at all sites are within the limits that Waterwatch identifies as healthy. however, after heavy rainfalls, storm water drains deposit much silt from roads, driveways, gardens, roofs etc.
- Dissolved oxygen is essential for creatures with gills – not only fish, but the tiny creatures (macroinvertebrates) that populate waterways (see below). The higher the water temperature, the lower the level of dissolved oxygen in water, so there is a link here to turbidity.
Dissolved oxygen levels measured at all three sites are often below the 50% saturation threshold that is considered healthy for freshwater streams. Lack of riffles in a flowing creek undoubtedly lessens the DO, particularly in summer when the estuary entrance is closed. Dissolved oxygen levels measured at the Augusta Street test site are slightly borderline but within the limits that Waterwatch identifies as healthy.
- Phosphorus is released by rotting organic matter and is essential for plant growth. Australian flora are adapted to the naturally low levels in Australian soils. But agricultural and garden fertilisers contain phosphorus to meet the higher needs of exotic crops and garden plants, and run-off can carry this into waterways. High levels of phosphorus support toxic algal blooms.
Phosphorus levels measured at the Augusta Street testing site are measured within the limits that Waterwatch identifies as healthy.
- Macroinvertebrates are the tiny but visible insects, worms, snails, shrimps, water fleas and the like that are a key part of the food chain in waterways. The diversity and abundance of these creatures is an excellent indicator of stream health.
Every six months BERG counts both numbers of species and numbers of macroinvertebrates in a sample of water from the Augusta Street testing site.
BERG’s testing shows sufficient numbers and range of species to indicate a healthy environment, though species are limited due to the salinity of the estuarine environment. Again, however, we have limited knowledge of what is normal in this environment.
More Questions to be Answered
In the future, BERG MM hopes to look more closely at what happens to water quality under a variety of conditions. For example, after heavy rain, does turbidity increase? If so, does this come from storm water draining into Harrap Creek, or from further up Balcombe Creek? How are the various water quality parameters affected by opening and closing of the Creek mouth? Does wind influence these readings?