Georges River

| Contents | Background | Consultation | Objectives | WQOs | RFOs | Glossary | Bibliography | Map | At a Glance |


Acid sulfate soils: include actual acid sulfate soils and potential acid sulfate soils. Actual and potential acid sulfate soils are often found in the same soil profile, with actual acid sulfate soils generally overlying potential acid sulfate soil horizons.

Alien species: See Introduced species.

Allocation: The volume of water a licence holder is entitled to extract during a year, subject to licence conditions and availability. Currently, only licence holders on regulated rivers supplied by irrigation dams have an allocation. (See also Off-allocation flows)

Allocation reliability: The long-term probability (over wet, dry and average years) of irrigators with 'normal security' water allocations being able to get a certain proportion of their nominal allocation by a specified date.

Alluvial aquifer/groundwater: Groundwater (or sub-surface water) contained in the alluvial deposits near a river. It is usually directly connected to the river and therefore its level is closely related to river levels. Alluvial aquifers can be recharged directly from the river under high-flow conditions. Under low-flow conditions, alluvial aquifers can provide base flow in the river channel.

Ambient waters: The ANZECC 2000 Guidelines define these as: "All surrounding waters, generally of largely natural occurrence". These include natural waterways, such as rivers, creeks, lagoons, wetlands and lakes (whether permanent, temporary, ephemeral or seasonal), groundwater and estuarine and marine waters. Ambient waterways can also include artificial waterbodies such as reservoirs and lakes, where these have community value for aquatic ecosystems or for human uses. Environmental values of water (in the form of the NSW Water Quality Objectives) apply to these waters.

Anabranch: A stream that leaves the main stream and re-joins it further down.

Anoxic: Containing low levels of oxygen.

ANZECC: Australian and New Zealand Environment and Conservation Council.

Aquifer: An underground layer of soil, rock or gravel able to hold and transmit water. Bores, spear-points and wells are used to obtain water from aquifers.

ARMCANZ: Agriculture and Resource Management Council of Australia and New Zealand.

Bank slumping: The falling or slumping of a riverbank into the river. May occur due to removal of riparian vegetation, erosion or bank destabilisation. The term is used here to denote slumping resulting from a rapid decrease in river height, in which water drains more quickly from the river than it does from the banks, which then collapse under their own weight.

Billabong: A backwater channel, often formed by a cut-off river bend, that forms a lagoon or pool when river levels fall.

Billion: a thousand million.

Bioaccumulate: The process by which chemical substances are taken up by living things and retained and concentrated as they move up through the food chain.

Biodiversity (biological diversity): The variety of all life forms, comprising genetic diversity (within species), species diversity and ecosystem diversity.

Biota: All living things, including micro-organisms, plants and animals.

Blue-green algae (cyanobacteria): Naturally occurring, microscopic, primitive photosynthetic 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 may become toxic.

Cap: A limit on the amount of water that may be diverted from the river for human uses, e.g. the Murray-Darling Basin Ministerial Council announced a cap on water use in the Murray-Darling Basin in 1995.

Catchment: The area of land drained by a river and its tributaries.

Channel capacity: The volume of water that can pass along the river channel at a certain point without spilling over the tops of the banks.

Confluence: The place where two or more streams flow together.

Contingency allowance: A volume of water reserved in a supply dam for release if and when needed for ecological and/or water quality reasons. For example, a release may be required to maintain water levels in a wetland to enable waterbirds to complete breeding, or to flush away an algal bloom.

Controlled streams: Streams where flow is usually controlled by upstream dams or diversion works, resulting in major changes to the natural flow patterns. These include regulated streams as defined in the NSW Water Act 1912, where water is released from storage to meet downstream irrigation needs.

Criteria: The ANZECC 2000 Guidelines define water quality criteria as"scientific data evaluated to derive the recommended quality of water for different uses. On this website, the term is used interchangably with the term "Trigger value" and "guideline level".

Crustaceans: Invertebrate animals that have segmented legs and hard shells, e.g. crabs, yabbies, prawns.

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 trees and dead branches from a watercourse.

Diatom: A type of very small algae that can be used as an indicator of water quality.

Dissolved oxygen: Oxygen in the water (which may be used by aquatic animals).

DLWC: NSW Department of Land and Water Conservation. Now named Department of Natural Resources (DNR).

DNR: Department of Natural Resources.

Draw-down(s): Volumes of water released or extracted from a pool or dam, thereby lowering the water level.

Dryland salinity: See Salinity.

Ecosystem: Any system in which living organisms and their immediate physical, chemical and biological environment are interactive and interdependent. Examples are ponds, forests and wetlands.

Effluent creek: A creek that leaves a watercourse and does not return to it (the opposite of a tributary). ('Effluent' in this sense has nothing to do with pollution.)

Electrical conductivity (or EC units): A measure of the ability of water to conduct an electric current between electrodes placed in the water; the value obtained relates to the nature and amount of salts present.

Environment: The Protection of the Environment Administration Act 1991 sets out a meaning of 'environment' as: 'Components of the earth, including:

  1. land, air and water
  2. any layer of the atmosphere
  3. any organic or inorganic matter and any living organism
  4. human-made or modified structures and
    areas, and includes interacting natural ecosystems that include components referred to in a-c.'

Environmental flows: Flows, or characteristics of the flow pattern, that are either protected or created for an environmental purpose.

Environmental impact statement: A document which describes a proposed development or activity, predicts the possible or certain effects of the activity on the environment, and outlines safeguards to mitigate or control environmentally damaging effects.

Environmental standard: A quantifiable characteristic of the environment against which environmental quality may be assessed.

Environmental valuation: Technique employed to estimate the worth of an environmental resource from the perspective of society as a whole in the absence of prices.

Environmental value: The ANZECC 2000 Guidelines define environmental vaues as: 'particular values or uses of the environment that are important for a healthy ecosystem or for public benefit, welfare, safety or health and that require protection from the effects of pollution, waste discharges and deposits. Several environmental values may be designated for a specific waterbody.

Ephemeral: Temporary or intermittent, for instance a creek or wetland that dries up periodically.

Escherichia (E.) coli: A type of faecal coliform bacteria (see below) which is found in large numbers in the faeces of humans and other mammals. It serves as a reliable indicator of recent faecal contamination of water.

Estuary: The part of a river in which water levels are affected by sea tides, and where fresh water and salt water mix.

Euphotic depth/zone: The lit region of a body of surface water. This extends from the surface down to the deepest level at which there is sufficient light for photosynthesis to occur.

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.

Fish ladder or fishway: A structure designed to enable fish to move over a physical barrier (dam or weir) in a waterway.

Flood channel: A natural channel in a floodplain, which carries flowing water only during a flood.

Floodplain: Flat land beside a river that is inundated when the river overflows its banks during a flood.

Floodrunners: Channels that run with water only during floods and very high flows.

Floods: Flows that are high enough at their peak to overrun river banks or cause flow through high-level anabranches, floodrunners or to wetlands.

Flow regime: The pattern of flow in a river which can be described in terms of quantity, frequency, duration and seasonal nature of water flows.

Freshes: Flows that produce a substantial rise in river height for a short period, but which do not overrun the river banks or inundate areas of land.

GMC: Groundwater Management Committee.

Great Artesian Basin: A vast, very deep store of underground water below much of the drier regions of eastern Australia.

Groundwater: Underground water filling the voids in rocks; water in the zone of saturation in the earth's crust.

Habitat: The type of environment in which a given animal or plant lives and grows, including physical and biological conditions.

Hard-surfacing: A hard, generally impermeable surface placed over soil-e.g. concrete or bitumen.

Headwaters: The small streams on the higher ground of a catchment, which flow into a river.

High flows: Higher than normal flows, which occupy much of the river channel or which overrun banks. In these guidelines, high flows in the middle and lower reaches of rivers are those that are greater than the level that long-term records indicate would naturally be exceeded 30% of the time (i.e. the 30th percentile).

High-security water use: Licensed entitlement to a more secure water supply than under normal-security licences, e.g. for horticulture and town water supplies.

HRC Healthy Rivers Commission now disbanded see NRC

Hydrographic shape: Describes the flow pattern of water, for example, after a short storm or runoff from prolonged rain.

Hydrology: The study of the distribution and movement of water.

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).

Invertebrates: Animals without backbones, including worms, insects, shrimps, crabs, snails, shellfish and zooplankton. Macroinvertebrates are large enough to be seen without the aid of magnification; microinvertebrates need to be viewed through a microscope.

Irrigation salinity: See Salinity.

Levee: A constructed embankment to prevent a river overflowing.

Low flows: Flows that occupy only a small portion of the river channel. Low flows would normally occur when there is little contribution to the river from rainfall events. For the purposes of the river flow objectives, the low flow is defined as the flow which occurs less than 20% of the total time that the river is flowing.

Macrophyte: A plant large enough to be seen without the aid of a microscope.

Median: The median is the middle value in a data set ranked from lowest to highest.

Megalitre (ML): One million litres (one Olympic swimming pool is approximately 2 ML).

Microbiological quality: In these guidelines, refers to the quality of water in terms of the level of disease-causing organisms it contains.

Multi-level offtake: An offtake structure within a dam, which can take water from various depths, rather than just one. For instance, if the offtake is only at the bottom of the dam, releases of water may be cold, deoxygenated and nutrient-rich. A multi-level offtake allows releases to be made from upper layers where water quality is often better.

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.

NHMRC: National Health and Medical Research Council.

Non-point source pollution: See Point-source pollution.

NRC: Natural Resources Commission - established in 2003 to provide independent advice to the NSW Government on natural resource management issues.

NRHP: National River Health Program.

NTU: Nephelometric turbidity unit (a unit of measurement for turbidity).

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.

NWQMS: National Water Quality Management Strategy. A joint initiative of the state and federal governments, to pursue sustainable use of the nation's water resources by protecting and enhancing their quality while maintaining economic and social development.

Off-allocation flows: Water that has not been released from storage, but comes from dam spills and/or inflows from tributaries below the dam. Licence holders are permitted to extract water from these flows but water so extracted is not debited against their allocation.

Off-allocation period: When access to flows (dam spills or tributary inflows downstream of dams) is permitted by licence holders without debit against their allocated volume. The DLWC announces the start of an off-allocation period, usually when flows are greater than are needed to meet on-allocation orders.

Offtake structure: A structure or point of diversion for water transfer. For instance, water is released from a dam via an offtake structure (see also multi-level offtake).

On-allocation: Water ordered by a licence holder and which will be debited against their actual allocation.

Pathogen: Disease-causing organism.

Percentile: In these guidelines, usually refers to flow duration curves. The horizontal scale of the graph is divided from 0 to 100 percentiles (or per cent of time), while the vertical scale is flow rate (often in ML/day). For example, when looking at flow rates, the 90th percentile is the daily rate that is exceeded on 90% of days at a specific location. If the 90th percentile is 13 ML/day, then the stream flow would be higher than 13 ML/day for 329 days per year, and lower for 36 days per year.

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.

Propagules: Parts of a plant (such as seeds, roots or stems) from which new plants can germinate.

Precautionary principle: The principle that the lack of scientific certainty should not be a reason to postpone preventive measures to avert threats of serious or irreversible environmental damage.

Pulsing supply: A strategy to reintroduce variability to releases of water from dams; introducing pulses of flow below dams allows a more natural flow pattern.

Ramsar Wetlands: Wetlands of international importance listed under the Ramsar Convention. To be put on the register, a wetland has to fulfil certain criteria-such as being important to the survival of migratory birds or endangered plant and animal species.

Raw water: Surface or groundwater that has received no treatment to make it suitable for drinking.

Recharge: Water that infiltrates through the soil surface to the watertable.

Recharge in-take bed: Areas like sandstone hills or gravelly river banks, which prolonged rainfall or high flows seep through to refill an underground waterbody.

Regulated: A river or creek where water is released from storage to meet diversion requirements downstream.

Regulator: A structure used to control the flow of water, for example, diverting water away from the main channel down an effluent creek.

Riffle: A shallow area of the river in which water flows rapidly over stones or gravel.

Riparian zone: The area along the bank of a river or a stream, which often has water-dependent vegetation.

River alluvium: Material deposited by a flood.

Sag: 'Dissolved oxygen sag'-a section of the river where dissolved oxygen levels are depleted, often below a pollution source.

Salinity: The concentration of salts in soil or water, including sodium chloride (NaCl). Dryland salinity is caused by clearing deep-rooted vegetation on areas of saline watertables. The uptake of water by plants is reduced, allowing the watertable with soluble salts to rise, killing plants and creating bare areas prone to erosion. Irrigation salinity occurs when irrigation raises the watertable, bringing high concentration of salt within root zones of plants, killing and stunting vegetation. It results from applying more water than can be used by the crop and by clearing of deep-rooted vegetation such as trees. Urban salinity is when rising watertables cause damage to infrastructure such as roads, underground pipes, houses and gardens. Urban salinity has been identified in NSW in 26 inland towns and in western Sydney.

Spear-point: A shallow bore inserted in soft sediments to draw up water.

State Environmental Planning Policy (SEPP) 14: NSW Government policy to ensure that the coastal wetlands are preserved and protected; prepared under the Environmental Planning and Assessment Act 1979.

Stressed river: Assessment made by the Department of Land and Water Conservation that determines appropriate management strategies for water allocation and flow management in uncontrolled streams. A classification based on environmental and water-use criteria.

Stratification: Distinct layers of water in a dam or weir pool, formed when there is little movement to cause intermixing-usually in summer when deeper layers of water become cold and deoxygenated. These changes may, in turn, induce other water quality changes.

Surface water: Water on the surface of the land, for example in rivers, creeks, lakes and dams.

Suspended solids: The smaller, lighter material such as clay, silt and fine sand carried in suspension in water.

Sustainable: (As applied to water resource management.) Management that will meet current needs while conserving natural ecosystems so they can also meet future needs.

Target (water quality): A level of water quality to be achieved in a specified time frame as a step towards the desired long-term objectives. It is derived from comparing available water quality data/information with the water quality objectives, and considers social and economic factors.

Top-release (of water): Better-quality water released from the top layers of a dam.

Tributary: A river or creek that flows into a larger river.

Trigger values: the ANZECC 2000 Guidelines state that: 'These are the concentrations (or loads) of the key performance indicators measured for the ecosystem, below which there exists a low risk that adverse biological (ecological) effects will occur. They indicate a risk of impact if exceeded and should 'trigger' some action, either further ecosystem specific investigations or implementation of management/remedial actions.' Note that on this website, the trigger values from the ANZECC 2000 Guidelines are also referred to as guideline levels or numerical criteria.

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.

Uncontrolled streams: Streams that are largely free of structures that control flow, such as major dams.

Urban salinity: See Salinity.

Variability: The likelihood of variation or change. High variability of river flows means that stream height at any one place can change substantially over time. Variability is determined by catchment size, number of tributaries, slope and climate. Overall, Australia has extremely variable rainfall and river flows. River management for consumptive uses has decreased variability.

Watertable: The upper surface of a groundwaterbody.

Water quality goal: A desired water quality outcome to help develop strategies for managing human activities that may affect the environment. Under the NWQMS, a chosen suite of environmental values for a catchment would constitute the water quality goals for that catchment.

Water quality objective: ANZECC 2000 Guidelines define Water Quality Objective as a "numerical concentration limit or narrative statement that has been estabilshed to support and protect the designated uses of water at a specified site." The NSW Water Quality Objectives endorse the environmental values (following extensive community consultation) recommended for each catchment and the ANZECC 2000 Guidelines should be used to estabilsh the technical criteria (guideline levels) that support or protect these values at a specified site. The NSW Water Quality Objectives are NOT lmiits.

Weir pools: The water held back by a weir, forming a still pool. Where the land is very flat, such as in western NSW, a weir can cause very long pools to form. For example, Maude Weir on the Murrumbidgee River is 6 m high and creates a weir pool 35 km long.

Wetland: Land inundated with temporary or permanent water that is usually slow moving or stationary, shallow, can be fresh, brackish or saline, and where the inundation affects the plant and animal communities and the type and productivity of soil.

WSP: Water Sharing Plan - a ten year statutory plan under the Water Management Act 2003 that defines how water is shared between users, and between users and the environment and establishes rules for access to that water.

This page was published 1 May 2006

2/05/2006 |