Biodiversity (or biological diversity): The variety of all life forms, comprising genetic diversity within a species, species diversity and ecosystem diversity
Biota: all living things including micro-organisms, plant and animals.
Blue-Green algae: Microscopic bacteria. Under certain conditions (including high nutrients, warm still water, strong sunlight into the water) they can bloom into a dense and visible growth and become toxic.
Deoxygenated: With most or all oxygen removed. Water becomes deoxygenated (i.e. loses its dissolved oxygen) for a number of reasons including stagnation, eutrophication and rising temperatures.
De-snagging: The removal of fallen and dead branches from a watercourse.
Dissolved oxygen: Oxygen in the water (which may be used by aquatic animals)
Environmental flows: Flows of water, that are either protected or created for an environmental purpose.
Eutrophication: Excessive levels of aquatic plant growth (including algae) resulting from raised levels of nutrients and other factors.
Extraction: Water taken from rivers for off-stream use or for consumption.
Faecal coliform: A type of bacteria found in faecal material of humans and other mammals. Faecal coliforms themselves generally do not make people sick. High levels indicate that water is likely to contain other micro-organisms that make people sick.
Indicator (e.g. water quality, biological, ecological): Any physical, chemical or biological characteristic used as a measure of environmental quality.
Introduced species: Species of plants or animals that are not native to Australia (also referred to as exotic or alien species).
Natural flow regime: The likely pattern of flow before European settlement in Australia. In these guidelines, natural flow regime refers to the flow patterns without any regulation or extraction of water.
Nutrients: Nutritional substances. Unnaturally high levels of nutrients, such as in a river below a sewage treatment plant, can encourage abnormally fast and prolific growth of algae in the water, or weed growth in the bush.
Pathogen: Disease-causing organism.
Point-source pollution: A single, identifiable source of pollution, such as a drain from an industrial site or sewage treatment plant (as opposed to non point-source or diffuse-source pollution-coming from many small sources over a large area).
Potable water: Water fit for human consumption.
Raw water: Surface or groundwater that has received no treatment to make it suitable for drinking.
Salinity: The concentration of salts in soil or water, including sodium chloride (NaCl).
Suspended solids: The smaller, lighter material such as clay, silt and fine sand carried in suspension in water.
Turbidity: A measure of the amount of the light-scattering properties of water. It indicates how much silt, algae and other material is suspended in water. Highly turbid waters may look muddy, stain clothes, block irrigation sprays and pipes or harm aquatic organisms.
Deputy Principal at a Sydney high school. Coordinating author of the new Geoactive book series.