Yass Valley
Indicator: Surface Water Quality
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What the results tell us for Yass Valley
The majority of the Yass Valley Council area is in the Murrumbidgee Catchment Management Authority and its rivers flow to the Murrumbidgee River catchment. Water from these river systems also sustain much of Upper Lachlan’s irrigated agriculture.
Three key determinants of surface water quality are; electrical conductivity, total phosphorus and turbidity levels. These were measured at three water quality monitoring sites in Yass Valley. Other physio-chemical parameters are also reported, including dissolved oxygen, pH, temperature and total suspended solids.
Other water quality sites have been sampled in Yass Valley, such as the Murrumbidgee River sites Burrinjuck Dam and Glendale, however no data was reported for these sites over the current reporting period.
Trends in surface water quality
Yass Valley surface water quality monitoring sites are at:
- Goodradigbee River at Wee Jasper (site number 410024)
- Murrumbidgee River at Halls Crossing (site number 410777)
- Yass River at Riverview (site number 41010898).
| Parameter* and location | Median values | Default trigger values ** | ||
|---|---|---|---|---|
| 1997–2000 | 2000–04 | 2004-08 | ||
| Goodradigbee River at Wee Jasper (410024) | ||||
| Dissolved oxygen (mg/L) | 11 | 9 | 9 | |
| Dissolved oxygen saturation (%) | 95 | 93 | 95 | Between 90-110 |
| Electrical conductivity (µS/cm) | 76 | 72 | 61 | 350 |
| pH | 7.6 | 7.6 | 7.5 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 14 | |
| Total phosphorus (µg/L) | 9 | 16 | 18 | 20 |
| Total suspended solids (mg/L) | 1 | 5 | 5 | |
| Turbidity (NTU) | 3 | 6 | 5 | 25 |
| Murrumbidgee River at Halls Crossing (410777) | ||||
| Dissolved oxygen (mg/L) | - | - | 9 | |
| Dissolved oxygen saturation (%) | - | 90 | 84 | Between 90-110 |
| Electrical conductivity (µS/cm) | - | 203 | 320 | 350 |
| pH | - | 8.1 | 8.1 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 8 | |
| Total phosphorus (µg/L) | - | 19 | - | 20 |
| Total suspended solids (mg/L) | - | 8 | - | |
| Turbidity (NTU) | - | 6 | 10 | 25 |
| Yass River at Riverview (410176) | ||||
| Dissolved oxygen (mg/L) | - | - | 10 | |
| Dissolved oxygen saturation (%) | - | 99 | 106 | Between 90-110 |
| Electrical conductivity (µS/cm) | - | 679 | 740 | 350 |
| pH | - | 8.4 | 8 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 18 | |
| Total phosphorus (µg/L) | - | 19 | 37 | 20 |
| Total suspended solids (mg/L) | - | 5 | 11 | |
| Turbidity (NTU) | - | 7 | 8 | 25 |
* µS/cm = microsiemens per centimetre; µg/L = microgram per litre; NTU = nephelometric turbidity unit; ** For information on default trigger values, see About the Data
Source: NSW Provisional River Data, 2008
Goodradigbee River at Wee Jasper
The median value for electrical conductivity at Wee Jasper reduced over the current reporting period. Similarly the pH value decreased as well, to an acceptable limit lower than the default trigger value (Table 1). The electrical conductivity trend has been consistent with the previous two reporting periods, falling slightly each time.
Overall the water quality has improved marginally at this site, with only the total phosphorus concentration increasing over the current reporting period.
Murrumbidgee River at Halls Crossing
The water quality at the Halls Crossing site on the Murrumbidgee River was worse in the current reporting period, when compared to the previous reporting period. The median value for the electrical conductivity significantly rose over the current reporting period, however this value was still under the default trigger value. Dissolved oxygen concentration also dropped below the lower limit of the default trigger value, over the current reporting period and pH remained above the upper default trigger value.
Yass River at Riverview
Yass River’s water quality monitoring sites, are listed as site number 410176 for the current reporting period, however in the previous report, it was listed as 41010898, which indicates that the station may have changed or there was an error in the reporting of data. Therefore comparisons between reporting years may not be accurate. The median value for electrical conductivity increased significantly to over twice the default trigger value. Similarly the total phosphorus concentration also increased significantly, to over the default trigger value, indicating that the water quality at the site decreased over the currently financial year. The pH levels did decrease over the current reporting period, however they are still above the default trigger values.
Other studies
One Waterwatch monitoring site is listed for Yass Valley Council. The site is at Wee Jasper which is also monitored by the NSW Department of Water and Energy. No additional data was available for Wee Jasper from Waterwatch.
About the data
Data for the monitoring sites covered in this report were from the NSW Department of Water and Energy (DWE) http://www.dwe.nsw.gov.au/
Data is routinely reported at http://nratlas.nsw.gov.au. DWE is responsible for quality control and on-going maintenance of the data collected in its databases.
Interpreting the data
Default environmental value
The Water Quality and River Flow Interim Environmental Objectives (EPA 1999) for NSW, which are still current, indicate that protection of aquatic ecosystems is the default environmental value for most water bodies in catchments associated with Yass Valley Council area. Although individual councils are free to assign additional or different value through local processes and based on site-specific information, so far no councils in the Australian Capital Region have done so.
Default trigger values
The default trigger values used in this report were those values set out in Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand (ANZECC and ARMCANZ) (2001). The values applicable to the Australian Capital Region are those for ‘south-east Australia for slightly disturbed ecosystems’ (ANZECC and ARMCANZ 2001). The default trigger values for different water quality parameters for the protection of aquatic ecosystems are based on the type of water body in question. Compared to most other environmental objectives, the protection of aquatic ecosystems is one that requires more stringent water quality guidelines.
The median value (i.e. middle value of a data series) for each monitoring site in the Council area over the reporting period was compared with the default trigger value from the guideline values suggested in ANZECC and ARMCANZ (2001). This approach was recommended when no environmental values were set, water quality objectives were not determined, local reference sites were unavailable and local site-specific information could not be sourced. This broad reporting approach cannot be used to assess 'compliance'; it is merely a warning system to alert natural resource managers.
The data was firstly sourced from the NSW Natural Resource Atlas, if the relevant data wasn’t available from this resource, the information supplied from the NSW Department of Water and Energy (DEW) was used. The data from the NSW Natural Resource Atlas generally provided daily data on stream flow and electrical conductivity, amongst others. Whereas the data supplied by the DEW had periodic samples of the data, however did include values for the turbidity and total phosphorus.
Electrical conductivity is a measure of the ability of water to conduct an electric current. This is considered an appropriate indicator of salinity, as it is proportional to the concentration of total dissolved salts in water.
Phosphorus is considered as a key indicator of eutrophication in Australian freshwaters because it is typically a limiting nutrient for primary production under natural conditions (Cullen 1986; Donnelly et al. 1992). Total phosphorus is analysed as it represents an aggregation of all fractions of phosphorus reaching the water column from various processes and it represents the potential maximum concentration of phosphorus available for biological uptake (NSW EPA 2000).
Australia has naturally turbid waters, owing to deeply weathered soils rich in clay-sized particles. These particles are readily transported to streams during storms. Because of their colloidal nature they remain suspended in the water column, resulting in high turbidity (Cullen 1986). In addition to natural causes, the turbidity of many waters has increased as a result of human-induced erosion through practices such as land clearing (agriculture and forestry), urbanisation, extractive industries and river regulation (Walker 1985). Turbidity is a measure of light scattering and absorptive properties of water, which are roughly proportional to the type and concentration of suspended matter. It is therefore commonly used as an indicator of the amount of suspended matter in the water column, although quantitative relationships between the two are difficult to define, because various types of suspended material have different light-scattering properties.
Additional data
Other potential sources of water quality monitoring data include the Community Access to Natural Resources Information (CANRI) website and the Waterwatch program.
References
Australian & New Zealand Water Environment & Conservation Council (ANZECC) (1992) Australian Water Quality Guidelines for Fresh & Marine Waters, Prepared for the National Water Quality Management Strategy
ANZECC & ARMCANZ (2001) Australian Water Quality Guidelines for Fresh & Marine Waters, Prepared for the National Water Quality Management Strategy
Australian Government (2008), Australian Natural Resources Atlas, viewed at http://www.anra.gov.au/index.html on 10 October 2008
ANZECC and ARMCANZ - see Australian & New Zealand Water Environment & Conservation Council and Agricultural and Resource Management Council of Australia and New Zealand
Cullen, P. 1986, ‘Managing nutrients in aquatic ecosystems: the eutrophication problem’, in Deckker P. & Williams W.D. (eds) Limnology in Australia, CSIRO, Melbourne, pp.539–554.
Donnelly, T.H., Caitcheon, G.G. & Wasson, R.J. 1992, ‘Algal blooms in inland Australian water systems: sourcing nutrients and turbidity’, in CSIRO Division of Water Resources Divisional Report 92/4, CSIRO, Canberra, pp.74–81
MDBC, 2008, Sustainable Rivers Audit – A report on the Ecological Health of rivers in the Murray-Darling Basin, 2004-2007, Murray Darling Basin Commission, SRA Report 1, June 2008. Viewed at http://www.mdbc.gov.au/SRA on 10 October 2008.
NSW EPA (2000) NSW 2000 State of the Environment Report – Waters Chapter
NSW NRA (2008), New South Wales Natural Resource Atlas: NSW Provisional River Data, viewed at http://nratlas.nsw.gov.au on 10 October 2008
Sydney Catchment Authority (2008), Annual Water Quality Monitoring Reports, New South Wales Government, Sydney Catchment Authority, viewed at http://www.sca.nsw.gov.au/water-quality/water-quality-monitoring-reports on 10 October 2008
Walker, K.F. 1985, ‘A review of the ecological effects of river regulation in Australia’, Hydrobiologia vol.125, pp.111–129
Waterwatch NSE (2006), Waterwatch NSW, view at http://www.waterwatch.nsw.gov.au/index.html on 10 October 2008
