DWE Home > Home > Water Management > Water quality >

Water quality

The quality of the waters in our rivers and aquifers is naturally influenced by inputs of salt and nutrients from the surrounding landscape. However, water quality can also be degraded by a wide range of factors including point sources (such as sewage discharge, mine wastes) and diffuse sources such as land clearing and cultivation, urban and agricultural development.

The regulation of river flow by major storages and weirs and the extraction of water have also influenced the quality of water with many rivers receiving less flow events and floods which naturally clean and flush the river. While for rivers, lowered water quality may only be a short–term problem, water in our groundwater systems has often been stored for thousands of years so any contamination has long-lasting impacts.

The department has many programs that assess water quality and try to improve it. The department through its water licences also require that contaminated irrigation or mining water not be returned directly to rivers and groundwater. The Department of Environment and Conservation licences the discharge of sewage and other point source pollution.

Eutrophication and algal blooms

Eutrophication is a process whereby a river, lake, estuary or marine waters receive excess nutrients, particularly phosphorus but also nitrogen, that can stimulate rapid growth of algae and aquatic weeds. This can promote blooms of algae of which some can be toxic to humans and animals, and result in fish and stock deaths, minor gastro–intestinal complaints and skin irritations in humans. Algal blooms and growth of large water weed can also reduce dissolved oxygen in water resulting in fish kills. Nutrients can come from fertilizers applied to agriculture and lawns; erosion of soil containing nutrients; and sewage treatment plant discharges and urban runoff. For more information about algal blooms and their management, go to Algal information.

The department monitors phosphorous at 195 sites across NSW and at many of these on a monthly basis. The map shows those areas where the phosphorous levels in 2005 regularly exceeded the recommended guidelines.

Percentage of times total phosphorus levels exceeded recommended guidelines at NSW sites

Source: DNR data 2003–05; SCA data 2005; Sydney Water Corporation data 2005

Salinity

Salt is a part of the landscape of NSW and in some rivers and aquifers high salinity levels are natural. For example salinity levels in groundwater aquifers can range from that of rainwater to more than 10 times that of sea water. But the rate of release of salt into our soils and water sources can be accelerated by tree clearing, intensive irrigation and discharge of saline wastewaters from industry, mines and sewerage treatment plants. Over-extraction from an aquifer can also cause intrusion from surrounding saline water.

Water for drinking should not have a salt concentration greater than 800 S/cm (electrical conductivity or EC) and at levels greater than 1500 S/cm EC is unsuitable for the irrigation of many crops and can damage aquatic ecosystems. The Salinity Audit of the Murray–Darling Basin published in 1999 predicted that salinity levels were rising and could cause serious problems for water use and the environment within 20 to 50 years. As a result the NSW government developed the NSW Salinity Strategy in 2000. This recognised that to slow down the increase in salinity, we need to:

protect and manage our native vegetation;
use our land so less water goes into the groundwater table;
use water more effectively and efficiently;
use engineering solutions;
make better use of land affected by salt; and
focus our efforts on priority salinity hazard landscapes.

The department is also operating and constructing a number of salt interception schemes (PDF 761KB).

In the State’s south-west, the Department of Water and Energy is developing a project that would see a local industry fund the ongoing operation of the Billabong Creek Salt Interception Scheme.

Shortly after the NSW Salinity Strategy, The Murray Darling Basin Ministerial Council agreed in 2001 to the Basin Salinity Management Strategy (BSMS). The BSMS established river salinity targets for each tributary valley, as well as the Murray Darling systems. These targets were intended to reflect the shared responsibility between the valley communities and between the States. The BSMS also established an accountability framework to monitor and assess the salinity impact of changes in land and water management. These changes are relative to a Baseline Condition.

Because of practical difficulties assessing changes by monitoring alone, the accountability framework is informed by computer models of the catchment and river systems of the Murray–Darling Basin. Between 2002-2004, the department developed salinity models of the major NSW tributaries of the Murray–Darling Basin. These models were based on the water management models developed using the department's Integrated Quality Quantity Model software. These models were externally reviewed and accredited under the Operational Protocols for Schedule C of the Murray Darling Basin Agreement (PDF 4MB).

The models defined the Baseline Conditions for salinity for NSW, and are able to assess the impacts of any changes in land and water management on flows and salinity. The reports describing the implementation of these models are available below.

Instream salinity models of NSW tributaries in the Murray-Darling Basin

Volume 1 – Border Rivers Salinity Integrated Quantity and Quality Model (PDF 4MB)
Volume 2 – Gwydir River Salinity Integrated Quantity and Quality Model (PDF 2.7MB)
Volume 3 – Namoi River Salinity Integrated Quantity and Quality Model (PDF 2.8MB)
Volume 4 – Macquarie River Salinity Integrated Quantity and Quality Model (PDF 3.5MB)
Volume 5 – Lachlan River Salinity Integrated Quantity and Quality Model (PDF 4.3MB)
Volume 6 – Murrumbidgee River Salinity Integrated Quantity and Quality Model (PDF 3.2MB)
Volume 7 – Barwon-Darling River Salinity Integrated Quantity and Quality Model (PDF 2.9MB)

The department monitors river salinity at a number of locations across NSW. The following table shows salinity levels at key river sites over recent years:

Recorded NSW River Salinity for selected locations from 2000 to 2003 and 2003 to 2006

Stream and Measuring Point	Mean daily river salinity levels (EC) for specified period
* indicates end of valley	Period of record	2000 to 2003	2003–2006#	Maximum @
Murrumbidgee at Balranald*	1992–2006	158	135	1133
Murrumbidgee at Wagga Wagga	1993–2006	142	135	521
Lachlan at Booligal*	1999–2006	545	723	1097
Lachlan at Forbes	1999–2006	472	552	1170
Barwon–Darling at Collarenebri	2002–2006	345**	300	533
Bogan at Gongolgon*	2000––2006	534	425	982
Macquarie at Carinda*	1999–2006	559	651	1207
Macquarie at Baroona	1999–2006	476	499	989
Castlereagh at Gungalman Bridge *	2001–2006	985**	531	1555
Namoi at Goangara*	1995–2006	495	395	1165
Namoi at Gunnedah	1995–2006	578	534	1170
Mehi at Bronte*	2001–2006	505**	511	966
Macintyre at Holdfast	2002–2006	349**	309	575
Hunter at Greta	1992–2006	672	690	1417

Source: DNR 2006.
Note: * indicates end of valley site
** indicates incomplete period of record
# data only available to March 2006
@ maximum spot readings

In general, the drought conditions since 2000 have reduced the mobilization of salt into our rivers.

Water temperature

The temperature of river water varies according to seasonal conditions. However an unnatural increase or decrease in water temperature can affect aquatic ecosystems. Most aquatic organisms are "cold-blooded" which means they are unable to internally regulate their core body temperature and natural temperature changes influence their biological activity and growth. Generally, the warmer the water temperature, the greater the biological activity. Temperature also affects water chemistry as very warm or cold water holds less oxygen which is important for survival of aquatic life.

Artificially cold temperatures can occur in a river downstream of a large dam as a result of the release of colder bottom water (known as hypolimnial water) from a dam. This can affect the river temperature and aquatic organisms, and fish breeding cycles for hundreds of kilometres downstream. DNR in cooperation with other agencies and dam operators is developing a strategy to mitigate the impacts of cold water pollution. For further information, go to cold water pollution.

Turbidity

Turbidity is a common water quality problem in NSW, particularly in the inland areas. Turbidity refers to how clear the water is - the greater the amount of total suspended solids in the water, the murkier or muddier it appears and the higher the measured turbidity. In most rivers turbidity increases after rainfall and flooding because of soil erosion. This can cause sedimentation of rivers and dams which can smother water plants. The suspended sediments can also absorb and transport nutrients, heavy metals, pesticides and other chemicals. Turbid water is a problem for country town water supplies - it is difficult and costly to remedy and may create heath problems.

Groundwater contamination

A particular risk to groundwater sources is contamination by leakage into the watertable of pollutants from industrial sites, fuel storage tanks, septic systems, land fill sites, garbage dumps, abattoirs, cattle feedlots and piggeries. The department maintains a list of groundwater contaminated sites which is used as a basis for determining where groundwater extraction can occur and any associated licensing conditions for nearby aquifers.

The department works with the Department of Environment and Climate Change in developing groundwater clean-up strategies for contaminated sites. Because of the numerous contaminated sites in the Botany Bay area the department is currently developing an overall management plan for the Botany Bay sand aquifers. The department has also developed maps for some catchments showing areas vulnerable to groundwater contamination to help in developing management strategies.

Castlereagh vulnerability map (PDF file)
Lachlan vulnerability map (PDF file)
Macquarie vulnerability map (PDF file)
Macintyre vulnerability map (PDF file)

For more information on the protection of groundwater quality refer to the NSW State Groundwater Quality Protection Policy (PDF file).

Water Quality Monitoring

The department conducts continuous monitoring of salinity and water temperature at around 180 river sites across NSW. At some 195 locations the department also samples other water quality parameters such as turbidity, phosphorous, pH on a regular or periodic basis. Water quality data is also collected from some of the department's groundwater monitoring bores. At times, water quality studies are also undertaken to assess specific water quality issues. For access to the river salinity and temperature data as well as information on other water quality data that has been collected go to Water data online In addition community programs have also collected water quality data through the Waterwatch program. The information collected by Waterwatch groups has been an important guide to programs that improve the health of our waterways including the adoption of local solutions ranging from fencing areas of riverbanks, eradicating weeds and invasive species, to identifying pollution and reducing the effects of runoff, or even changes to licence conditions of polluting industry.