Gundagai
Indicator: Surface Water Quality
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What the results tell us for Gundagai
The Gundagai Shire lies within the Murrumbidgee Catchment Management Authority area. The rivers in this catchment form part of the Murrumbidgee River catchment. The water in the Shire’s rivers sustains the regions irrigated agriculture.
Three key determinants of surface water quality are, electrical conductivity, total phosphorus and turbidity levels. These were messured at nine sites in Gundagai. Other physio-chemical parameters are also reported, including dissolved oxygen, pH, temperature and total suspended solids.
Trends in surface water quality
Gundagai Shire surface water quality monitoring sites are:
- Adelong Creek at Bareena (site number 41010890)
- Adjungbilly Creek at Darbalara (site number 410038)
- Hillas Creek at Mundarlo Rd Bridge (site number 41010809)
- Murrumbidgee River at Gobarralong (site number 41010138)
- Murrumbidgee River upstream of Gobarralong Bridge (site number 410195)
- Murrumbidgee River at Gundagai (site number 410004)
- Murrumbidgee River downstream of Tumut River junction (site number 41010394)
- Muttama Creek at Coolac (site number 410044)
- Tumut River upstream of the Murrumbidgee junction (site number 41010891).
| Parameter* and location | Median values | Default trigger values ** | ||
|---|---|---|---|---|
| 1997– 2000 | 2000–04 | 2004-08 | ||
| Adelong Creek at Bareena (41010890) | ||||
| Dissolved oxygen (mg/L) | - | - | 8 | |
| Dissolved oxygen saturation (%) | 83 | 80 | 81 | Between 90-110 |
| Electrical conductivity (µS/cm) | 198 | 195 | 215 | 350 |
| pH | 7.4 | 7.4 | 7.3 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 16 | |
| Total phosphorus (µg/L) | 47 | 53 | 63 | 20 |
| Total suspended solids (mg/L) | 34 | 23 | 20 | |
| Turbidity (NTU) | 32 | 22 | 21 | 25 |
| Adjungbilly Creek at Darbalara (410038) | ||||
| Dissolved oxygen (mg/L) | - | 9 | 9 | |
| Dissolved oxygen saturation (%) | - | 92 | 92 | Between 90-110 |
| Electrical conductivity (µS/cm) | - | 145 | 127 | 350 |
| pH | - | 7.7 | 7.6 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 18 | |
| Total phosphorus (µg/L) | - | 39 | 59 | 20 |
| Total suspended solids (mg/L) | - | 8 | 11 | |
| Turbidity (NTU) | - | 9 | 11 | 25 |
| Hillas Creek at Mundarlo Rd Bridge (41010809) | ||||
| Dissolved oxygen (mg/L) | 9 | 9 | 9 | |
| Dissolved oxygen saturation (%) | 97 | 96 | 98 | Between 90-110 |
| Electrical conductivity (µS/cm) | 250 | 239 | 238 | 350 |
| pH | 7.9 | 7.9 | 7.9 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 24 | |
| Total phosphorus (µg/L) | 55 | 53 | 68 | 20 |
| Total suspended solids (mg/L) | 17 | 11 | 10 | |
| Turbidity (NTU) | 17 | 8 | 11 | 25 |
| Murrumbidgee River at Gobarralong (41010138)# | ||||
| Dissolved oxygen (mg/L) | 11 | 9 | 8 | |
| Dissolved oxygen saturation (%) | 95 | 93 | 105 | Between 90-110 |
| Electrical conductivity (µS/cm) | 332 | 295 | 262 | 350 |
| pH | 7.7 | 7.9 | 7.7 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 27 | |
| Total phosphorus (µg/L) | 212 | 20 | 58 | 20 |
| Total suspended solids (mg/L) | 12 | 8 | 13 | |
| Turbidity (NTU) | 14 | 10 | 10 | 25 |
| Murrumbidgee River upstream of Gobarralong Bridge (410195) | ||||
| Dissolved oxygen (mg/L) | - | - | 9 | |
| Dissolved oxygen saturation (%) | - | 87 | 90 | Between 90-110 |
| Electrical conductivity (µS/cm) | - | 145 | 259 | 350 |
| pH | - | 7.7 | 7.6 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 17 | |
| Total phosphorus (µg/L) | - | 39 | 29 | 20 |
| Total suspended solids (mg/L) | - | 8 | 16 | |
| Turbidity (NTU) | - | 9 | 13 | 25 |
| Murrumbidgee River at Gundagai (410004) | ||||
| Dissolved oxygen (mg/L) | 9 | 9 | 9 | |
| Dissolved oxygen saturation (%) | 95 | 92 | 95 | Between 90-110 |
| Electrical conductivity (µS/cm) | 140 | 114 | 82 | 350 |
| pH | 7.4 | 7.4 | 7.2 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 15 | |
| Total phosphorus (µg/L) | 25 | 44 | 18 | 20 |
| Total suspended solids (mg/L) | 20 | 23 | 6 | |
| Turbidity (NTU) | 40 | 10 | 6 | 25 |
| Murrumbidgee River downstream of Tumut River junction (41010394) | ||||
| Dissolved oxygen (mg/L) | - | 10 | 9 | |
| Dissolved oxygen saturation (%) | - | 95 | 95 | Between 90-110 |
| Electrical conductivity (µS/cm) | - | 72 | 133 | 350 |
| pH | - | 7.3 | 7.2 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 16 | |
| Total phosphorus (µg/L) | - | 22 | 21 | 20 |
| Total suspended solids (mg/L) | - | 9 | 10 | |
| Turbidity (NTU) | - | 8 | 9 | 25 |
| Muttama Creek at Coolac (410044) | ||||
| Dissolved oxygen (mg/L) | 10 | 7 | 8 | |
| Dissolved oxygen saturation (%) | 96 | 75 | 78 | Between 90-110 |
| Electrical conductivity (µS/cm) | 1575 | 1494 | 1085 | 350 |
| pH | 8 | 8.1 | 8 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 15 | |
| Total phosphorus (µg/L) | 117 | 134 | 147 | 20 |
| Total suspended solids (mg/L) | 32 | 25 | 15 | |
| Turbidity (NTU) | 30 | 21 | 13 | 25 |
| Tumut River upstream of the Murrumbidgee junction (41010891) | ||||
| Dissolved oxygen (mg/L) | - | - | 9 | |
| Dissolved oxygen saturation (%) | 94 | 95 | 93 | Between 90-110 |
| Electrical conductivity (µS/cm) | 41 | 28 | 51 | 350 |
| pH | 7.3 | 7.2 | 7 | Between 6.5 - 7.5 |
| Temperature (degrees C) | - | - | 15 | |
| Total phosphorus (µg/L) | 20 | 20 | 21 | 20 |
| Total suspended solids (mg/L) | 9 | 6.5 | 10 | |
| Turbidity (NTU) | 12 | 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; # = only one sample taken during the reporting period
At each site the water quality is assessed by comparing the median values of the electrical conductivity, total phosphorus and turbidity over the reporting period to the default trigger values (Table 1). It was found that Gundagai Shire did not meet the majority of these trigger values, which is also consistent with the previous reporting period. The following observations are made about the median values for the current reporting period:
- The dissolved oxygen saturation percentage was below the lower limit of the default trigger values for Adelong Creek at Bareena, and Muttama Creek at Coolac sites. These values were also below the lower limit of the default trigger values for the previous reporting period.
- The Gobarralong site on Murrumbidgee River only had one sample taken over the entire reporting period, therefore it is likely that the results obtained are not truly representative of the actual conditions of at the site for the current reporting period. This is shown by the variable results over the three reporting periods.
- Total phosphorus concentrations significantly exceeded the default trigger values at Adelong Creek, Adjungbilly Creek, Hillas Creek, the Gobarralong site on Murrumbidgee River, and Muttama Creek, where the concentration was at least three times greater than the default trigger value. The Muttama Creek site, the concentration was over seven times the default trigger value.
- The Gundagai site on the Murrumbidgee River, significantly decreased its median value for electrical conductivity.
- The majority of the other physio-chemical parameters median values were also within the default trigger values in Cooma-Monaro, for the current reporting period, with the exception of pH at Adjungbilly Creek, Hillas Creek, Murrumbidgee River at the Gobarralong and Gobarralong Bridge sites, and Muttama Creek, where the upper pH limits were exceeded.
Although some parameters at some sites had improved since the previous reporting period, many parameters have deteriorated since 2004. The exceedences are likely to be caused by reduced natural flows in the rivers due to drought conditions. Low river levels over an extended period of time release nutrients from the bed silt, which may have also contributed to the poor water quality. Overall, the results show that surface water quality in Gundagai Shire Council are generally poor during the reporting period, 2004-2005 to 2007-2008.
These results should provide natural resource managers with the motivation to undertake and invest in collaborative solutions to improve the quality of river water.
Other studies
Three Waterwatch sites exist in Gundagai Shire Council, all in the Murrumbidgee River catchment, at Adjungbilly-Bongongo, Cootamundra Sewage Treatment Plant outlet and Muttama Creek at Brawlin.
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 the Shire. 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 (ANZECC) and Agriculture and Resource Management Council of Australia and New Zealand (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 Shire 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 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
ANZECC - see Australian and New Zealand Environment and Conservation Council
ARMCANZ – see Agriculture and Resource Management Council of Australia and New Zealand
Australian and New Zealand Water Environment and Conservation Council (ANZECC) (1992) Australian Water Quality Guidelines for Fresh and Marine Waters, Prepared for the National Water Quality Management Strategy
Australian and New Zealand Environment and Conservation Council and Agricultural and Resource Management Council of Australia and New Zealand (ARMCANZ) (2001) Australian Water Quality Guidelines for Fresh and 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 7 October 2008
Cullen, P. 1986, ‘Managing nutrients in aquatic ecosystems: the eutrophication problem’, in Deckker P. and Williams W.D. (eds) Limnology in Australia, CSIRO, Melbourne, pp.539–554.
Donnelly, T.H., Caitcheon, G.G. and 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 – see NSW Environment Protection Authority
NSW NRA – see NSW Natural Resource Atlas
NSW Environment Protection Authority (2000) NSW 2000 State of the Environment Report – Waters Chapter
NSW Natural Resource Atlas (2008), New South Wales Natural Resource Atlas: NSW Provisional River Data, viewed at http://nratlas.nsw.gov.au on 7 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 7 October 2008
