Indicator: Surface water quality

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What the results tell us for Tumut

Graphs of water quality data |

See also:
| Aquatic macro-invertebrates | Discharges to waters | Drinking water quality |

For maps showing the location of water quality monitoring sites, Contact us for details of the full report for the Australian Capital Region (available only on CD-ROM).

Surface water quality is generally good in Tumut Shire, and has remained so over the periods 1993–97 and 1997–99 at Site 41010976, Tumut River – a site monitored over time by DLWC.

Tumut Council commenced monitoring at a number of sewer discharge sites only during the reporting period, so comparative data for two time-slices at these sites are not available. Limited data were obtained at these sites, and the absence of faecal coliform data leaves a question mark about the adequacy of treatment.

About the data

Tumut Council monitors the following sites and collects and maintains on-going records.

• Site number Tm1 – Tumut sewer discharge, Tumut River
• Site number Tm2 – Adelong sewer discharge, Murrumbidgee River
• Site number Tm3 – Batlow sewer discharge, Murrumbidgee River
• Site number Tm4 – Talbingo sewer discharge, Tumut River
• NSW DLWC monitors Site number 41010976 in the Tumut River, and collects and maintains on-going records.

Water Quality and River Flow Interim Environmental Objectives were developed for Tumut by NSW EPA early in 2000, but uses and values applicable to the sites were not introduced by DLWC for this report. Criteria for water quality used by both DLWC and the Interim Environmental Objectives are those provided under the National Water Quality Management Strategy. They are listed in the Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC 1992), currently under review.

The EPA acknowledges in the Interim Environmental Objectives that the ANZECC (1992) guidelines need to be adapted to local conditions, and that further refinement of the numerical criteria is needed, especially for aquatic ecosystems, and particularly in places, or for issues, requiring priority action.

Description: What does 'surface water quality' measure?

Which data are collected?

• levels of selected substances in water at all relevant water quality monitoring sites in streams, estuaries and the sea

Why do we report this indicator?

The quality of surface water influences not only the health of aquatic ecosystems, but also whether that water can safely be used for drinking, agriculture, or recreation. Surface waters are streams (lakes and rivers), estuaries and the sea. The amounts of selected substances in surface water indicates the impact of human settlements and landuse on the environment, provided any "natural" sources are taken into account.

The suite of substances that should be monitored and reported is:

• concentration of all forms of nitrogen
• concentration of all forms of phosphorus
• concentration of total suspended solids (for streams only)
• turbidity in NTUs (for streams and estuaries only)
• water acidity
• water temperature
• water salinity, measured as electrical conductivity (for streams only)
• faecal coliform counts
• concentration of dissolved oxygen.

Exceedences of relevant guidelines should be reported separately for each of these susbstances against specified uses. In the Australian Capital Region, these uses (or values) are: aquatic ecology, recreation, aquaculture, agriculture (irrigation, water supply, livestock water supply), drinking water for humans. Each substance is important, and they are reported as part of one indicator to simplify reporting of the results. Any significant trends should also be reported separately for each substance as these trends reflect a change in water quality, and thus a change in the condition of the environment.

Levels of dissolved oxygen, for example, indicate the stress on aquatic life, with the potential for fish to die when levels of dissolved oxygen fall below four mg/L. Erosion and sediment transport are indicated by levels of total suspended solids and turbidity. Phosphorus levels are used to indicate potential algae problems in streams due to nutrient accumulation. Changes in salinity levels can indicate rising groundwater and soil salinity.

Many of these substances have significant natural sources, and these should be taken into account when assessing the data. For example, phosphorus-rich soils contribute much of the phosphorus in surface waters. Many Australian rivers have naturally high amounts of salt, making them marginally saline; and the amount of sediment in streams is also generally high, particularly during floods, resulting in high levels of turbidity and total suspended solids.

Major anthropogenic sources of these substances to Australian streams include soil erosion, agricultural fertilisers and sewage. These factors affect levels of phosphorus, nitrogen, total suspended solids and turbidity in particular. There is also some effect of sewage discharge on dissolved oxygen levels. Concentrations of other substances can also change due to these factors.