What's that in the Water


A simple guide of aquatic phenomena in the area and when and who you should notify if you suspect pollution is occurring.

Clear Water

Clear water has less dissolved and suspended material. Mountain creeks are often clear, because they run over bare rock without sediment or vegetation. Shallow water also tends to be clear because there is not enough depth for the long, blue wavelengths of light to travel and be reflected back.

Clear Water


Clear Brown or Reddish Water

Sometimes water is clear but brown like tea. The colour is the result of dissolved organic material from the breakdown of plants and animals. The material leaches into slow moving streams and lakes from surrounding forests, and wetlands, and stains the water brown or reddish brown.

Clear Brown or Reddish Water

Green Water

Suspended particles of living material can impart a hue to the water. Green water probably has a large population of algae (microscopic plants). Algae and other microscopic organisms have coloured pigments. When they grow in large numbers ("bloom"), they can colour certain areas or entire waterways. Blooms of an organism called Euglena may appear red. A bloom of diatoms, a kind of algae, can look brown.

Green Water

Turbid Water (sometimes grey or brown)

Turbidity in open water may be caused by growth of phytoplankton. 

Human activities that disturb land, such as construction, can lead to high sediment levels entering water bodies during rain storms due to storm water run-off. Areas prone to high bank erosion rates as well as urbanised areas also contribute large amounts of turbidity to nearby waters, through storm water pollution from paved surfaces such as roads, bridges and parking lots. 

If you suspect turbid water is not from a natural cause you should inform Council.

Turbid Water sometimes grey or brown

Slime, Fluff & Algae

Orange Slime or Fluff

Orange fluff is produced by a group of bacteria that use iron as an energy source. This is the same group of bacteria that create oily sheen's. The masses of bacteria excrete slimy or fuzzy-looking material as they grow and reproduce, and the slime becomes coated with rusty iron hydroxide. This is usually a natural phenomenon and is generally associated with acidic soils. In some areas, iron-rich groundwater may seep to the surface, and the iron drops out as it becomes exposed to air. In this case, the iron will appear as an orange crust or stain, and will not be fuzzy-looking.

Orange Slime

Orange Slime Caused by Iron Bacteria

Further information on Iron Bacteria can be found on the Iron Bacteria Web page.


Green hair like strands and green clumps are formed by filamentous algae. These colonies of microscopic plants live in shallow water on the bottom near shore or on submerged objects. Blue Green Algae can present like a paint like presence or strong colour in the water. 

A key to identifying algae species in our waterways can be found at NSW Water. 

Should You Be Concerned About Algae? 

The presence of algae in a waterway does not necessarily mean the water is polluted. A diverse community of algae is healthy. Algae are an important source of food and oxygen for other plants and animals in the water. Sometimes, certain conditions might favour a species that is normally rare in a waterway. With the right temperature, light, and nutrients in the water, the rare organism might multiply rapidly, forming a bloom. When an algae bloom is persistent or occurs routinely, too many nutrients may be entering the water. Nutrients (especially phosphorus) fertilise a waterway just as they fertilise your lawn or garden, causing microscopic plants in the waterway to grow. 

If you suspect the algae is the result of pollution you should inform Council.

Pollen, Oily Sheen's & Foam


A yellowish powder or dust on the surface of water in spring and early summer is probably pollen from trees. Pollen can also collect in clumps or blobs. After becoming water-logged, the pollen sinks to the bottom or may collect in shallows along the banks. Lines of pollen may be left on rocks as water levels drop. 

Oily Sheens

An oily sheen that reminds you of rainbow puddles in an asphalt parking lot might be from spilled petroleum. A minor spill is usually enough to form a film across the surface of large waterway. Oily sheens can also come from natural sources. Some bacteria (Leptothrix discophora) that live in waterlogged places get their energy from iron and manganese, and as these harmless bacteria grow and decompose, the iron may appear oily or form red or orange films, fluffs, and coatings. 

How to tell the difference between petroleum spills and natural oil sheens? 

Poke the sheen with a stick. If the sheen swirls back together immediately, it's petroleum. If the sheen breaks apart (shatters, or forms many sided fragments) and does not flow back together quickly, it is from bacteria or other natural source. 

If you suspect the sheen is not from a natural source you should inform Council.

Natural oily sheen

Photo showing natural oily sheen fracturing when broken with a stick.


Natural oily sheen fractured

 Photo showing natural oily sheen fractured and the brown fluffy evidence of Iron bacteria.


Foam is often seen along lake shores and on streams and rivers. Most foam is natural and does not indicate pollution. Foam forms when water is mixed with air, such as by a waterfall or waves breaking against shore. Plants and animals release organic compounds as they decompose, and these compounds lessen the surface tension of water and create bubbles. Biodegradable detergents and reduction of pollution from wastewater treatment plants have reduced the occurrence of pollution-related foam. 

If the foam smells fragrant or perfume, it may be from a nearby spill or waste discharge pipe. Natural foam may smell fishy or earthy, and may be white, off-white, or brownish, and breaks apart easily when disturbed. 

If you suspect the foam is not from a natural source you should inform Council.


Identifying Algae Blooms

WaterNSW has information to help identify different types of algae in waterways.

Blue-Green algae can pose a health risk to humans and animals, if you suspect you have an algae bloom do not drink the water.

Useful information if you suspect you have a blue-green algae bloom.

Managing Blue Green Algae in Farm Dams(PDF, 53KB)

NSW Health Recreational Water Quality

WaterNSW Algae Contacts

Should I Notify Council?

If you have gone through this simple guide and suspect water pollution to be occurring in a particular waterway, or are unsure of the cause of to phenomena in a waterway, an action request can be submitted to Council.