Search
Estuaries are the place where the freshwater from our catchments meet the saltwater of the sea.
Glenelg Hopkins CMA collects readings and observations for the Hopkins, Merri, Yambuk, Fitzroy, Surry and Glenelg estuaries and compiles a snapshot of estuary condition. More detailed estuary profiling is conducted once a month.
Regular observation, measurement and evaluation of our waterways over time provides information on the health of our catchments. This information assists with the maintenance and rehabilitation of our waterways.
To see the latest edition of Estuary Update click here
Previous editions of Estuary Update
To see the latest monthly profiling for your local estuary, click on the estuary links below.
Previous editions of Monthly Profiling
Hopkins
Merri
Yambuk
Fitzroy
Surry
Glenelg
Constant monitoring of estuary condition is vital. Factors looked at when assessing an estuaries health are:
- Depth
- Temperature
- Dissolved Oxygen (DO)
- Turbidity
- pH
- Total Dissolved Solids (TDS)
Temperature
Temperature of a water body directly affects many physical, biological and chemical characteristics.
Temperature directly affects the metabolic rate of plants and animals. Aquatic species have evolved to live in water of specific temperatures. If the water becomes colder or warmer, the organisms do not function as effectively, and become more susceptible to toxic wastes, parasites and diseases. With extreme temperature change, many organisms will die. Changes in long-term temperature average may cause differences in the species that are present in the ecosystem.
Dissolved Oxygen (DO)
Dissolved oxygen is a measure of the quantity of oxygen present in water. Oxygen is essential for almost all forms of life. Aquatic animals, plants and most bacteria need it for respiration (getting energy from food), as well as for some chemical reactions. The concentration of dissolved oxygen is an important indicator of the health of the aquatic ecosystem. Persistently low dissolved oxygen will harm most aquatic life because there will not be enough for them to use.
In some circumstances, water can contain too much oxygen and is said to be supersaturated with oxygen. This can be dangerous for fish. Supersaturated conditions occur in highly turbulent waters in turbines and at spillways, because of aeration, and also on sunny days in waters experiencing algal blooms or with many aquatic plants, because of photosynthesis. In this supersaturated environment, the oxygen concentration in fishes' blood rises. When the fish swim out into water that has less dissolved oxygen, bubbles of oxygen quickly form in their blood, harming the circulation.
Turbidity
In general, the more material that is suspended in water, the greater is the water's turbidity and the lower its clarity.
Suspended material can be particles of clay, silt, sand, algae, plankton, micro-organisms and other substances. Turbidity affects how far light can penetrate into the water. It is not related to water colour: tannin-rich waters that flow through peaty areas are highly coloured but are usually clear, with very low turbidity. Measures of turbidity are not measures of the concentration, type or size of particles present, though turbidity is often used as an indicator of the total amount of material suspended in the water (called total suspended solids). Turbidity can indicate the presence of sediment that has run off from construction, agricultural practices, logging or industrial discharges.
pH
pH is a measure of acidity (or alkalinity). Pure water has a pH of 7, acidic solutions have lower pH values and alkaline solutions have higher values. Values of pH range from 0 (highly acidic) to 14 (highly alkaline). Where water has no net alkalinity or acidity it is said to be neutral and has a pH of 7.
Total Dissolved Solids (TDS)
TDS is a measurement of all suspended organic and inorganic solids smaller than 2 micrometres (μm) within a solution. Although an important parameter, TDS is not a direct indication of water quality, especially when dealing with estuarine or marine waters. TDS is more commonly used in freshwater streams, lakes and reservoirs where the water is intended for consumption. It is related to more aesthetic characteristics such as colour and clarity; characteristics that may affect potability. Total dissolved solids can be leached from stormwater runoff and agricultural runoff but are also found naturally leaching from rocks within soils. Values below 500mg/L are usually acceptable for human consumption.