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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Water resources - Quality - Queensland
Basin: Ross River
Surface water quality in Ross River
Attributes for which exceedance analyses could be determined:
Salinity, pH, Total Phosphorus, Total Nitrogen, Turbidity
Attributes for which trend analyses could be determined:
Salinity
The Ross River Basin is located in the North East Coast Drainage Division. Apart from the ranges themselves, the catchment is relatively flat and gently sloping. Medium density native vegetation is present over most of the catchment with sufficient grasslands for cattle grazing. The lower catchment is heavily urbanised with Townsville bordering on the north-west bank. There is negligible agriculture in the catchment.
Monitoring data for the exceedance analysis were available from three sites, which are all confined to the lower and middle reaches of the Bohle River. Together, these sites represent approximately 51% of the basin. A trend analysis was not conducted for this basin.
At all of the monitored sites, surface water salinity levels were found to be within ANZECC (1992) and NHMRC (1996) targets for aquatic ecosystem protection, drinking water and agricultural use.
The data indicate that turbidity levels throughout most of the monitored catchment exceed the NHMRC (1996) guidelines for drinking water, however, in terms of aquatic ecosystem protection, these levels are good (ANZECC 1992).
From the limited data available, both TN and TP levels were found unsuitable for aquatic ecosystem protection (ANZECC 1992). Reasons for this are not entirely known but may be partially attributable to point discharges and stormwater runoff from the urban centre located upstream from and adjacent to the sites.
pH levels were found to be within ANZECC (1992) and NHMRC (1996) targets.
| Monitoring Station | Salinity - Electrical conductivity | Total nitrogen | Total phosphorus | Turbidity | pH | Blue Green Algae | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Exceed | Trend | Exceed | Trend | Exceed | Trend | Exceed | Trend | Exceed | Trend | Exceed | Trend | |
| 11810690619 | Good | No Data | Poor | No Data | Poor | No Data | Poor | No Data | Fair | No Data | No Data | No Data |
| 11810694667 | Good | No Data | No Data | No Data | No Data | No Data | Poor | No Data | Good | No Data | No Data | No Data |
| 11810686637 | Good | No Data | Poor | No Data | Poor | No Data | Poor | No Data | Fair | No Data | No Data | No Data |
| 118003A | No Data | No Data | No Data | No Data | No Data | No Data | No Data | No Trend | No Data | No Data | No Data | No Data |
Select a station name in the table above to view a detailed station report.
Monitoring Water Quality Guideline exceedances and trends
Exceedance Classification
For the Audit assessment of surface water quality, individual monitoring sites were classified as good, fair or poor for each variable based on whether State and Territory water quality guidelines (see below) were exceeded. Generally a 'good' classification was achieved where water quality was within guidelines for a greater period of time while a 'poor' classification resulted where water quality did not fall within the guidelines for a greater period of time. A range of statistical measures including the median, 90th percentile, and % time exceedance, were used by States and Territories for this determination dependent upon the variable and whether the analysis was based on assessing acute (short term extreme event) or chronic (long term sustained event) water quality impacts. 'Fair' water quality describes situations intermediate between good and poor. Full discussion of the methods used for water quality exceedance and trend assessment are presented in the Water Quality Technical Report (see link to technical report).
Water quality Trends
Detecting trends in surface water quality is complicated by seasonal climatic variation and the influence of stream flows on the observed concentrations of water contaminants. For these reasons a long term (~10 year) data set containing relatively frequently collected water quality samples (monthly as a minimum) and concurrent flow data are required to support trend assessments. A range of statistical analyses were used by States and Territories to report on water quality trends, dependent upon the nature of the monitoring (i.e., flow based versus regular sampling) and quality of the data (i.e., the method's ability to accommodate missing data values). All used methods that accounted for seasonality and stream flow influences (see link to technical report).
The significance of observed trends were assessed statistically to ensure they were not the result of random variation. Significant trends were reported in terms of their magnitude (i.e., how much change per annum) and their direction i.e. whether they were increasing or decreasing. Results that indicated no trends were also reported.
Result Aggregation
To be able to build an overview of State and National water quality it was necessary to aggregate water quality results from individual sites to river basins. To do this an 'upstream area weighting' method was used. Results obtained from a monitoring station were multiplied by the amount of catchment area that it samples. Weighted results from individual monitoring stations allows a river basin to be characterised in terms of the percentage of area classified as good, fair or poor, or in terms of the area undergoing increasing or decreasing trends for a particular water quality variable. Results per basin are presented graphically as colored pie charts.
This method was supported and adopted by State and territory agencies when compiling the national assessment and can be rationalised in terms of the way water quality interacts within a basin. Nevertheless, the potential for error generation was recognised, particularly when monitoring station coverage across the basin is limited, the opportunity for bias in the characterisation of basin water quality increases. This may lead to the underestimation of the extent of a water quality issue where monitoring stations are not placed within impacted areas, or alternatively overestimation, where in the absence of upstream monitoring stations, results obtained by impacted lowland sites are used to characterise the upper basin.
The Water resources - Quality - Queensland's reporting capacity to interrogate data down to an individual monitoring site scale provides the opportunity for basin wide aggregations presented elsewhere to be further examined.
- Salinity
- Surface Water pH
- Nutrients
- Turbidity
- Faecal Coliforms
- Blue-green Algae
List of attributes:
Note: some attribute information may not be available for some areas
Trend Legend
Exceedance Legend
Salinity
Trend
Salinity describes the salt concentration in water. It is usually measured in terms of the ability of water to conduct an electrical current (electrical conductivity EC) in units of micro siemens per cubic centimetre (m Scm-1). EC is an appropriate indicator of salinity, as it is proportional to the concentration of total dissolved salts and is easily measured in the field or by later laboratory analysis. Salinity is also sometimes measured directly (as is the case in Western Australia) in terms of total dissolved salts (TDS).
The salinity guideline for the protection of aquatic ecosystems was used for the exceedance assessment. The values for this water quality indicator are also generally equivalent for the indicators values for drinking water and agricultural water use, although the latter can be crop specific. Guideline boundaries varied from State to State (see below) reflecting the variability of surface water conditions and management objectives.
The two pie charts present salinity results aggregated from individual monitoring stations to represent the salinity status of the entire basin. They show the relative proportion of the basin area that was classified as having good, fair or poor water quality in terms of salinity guideline exceedances and the relative proportion of the basin area that was assessed as having increasing, decreasing or static salinity trends.
The proportion of the basin for which no data was available is also presented and provides an indication of the monitoring coverage of the basin for salinity.
Exceedance
Surface Water pH
Trend
The acidity or alkalinity of surface waters is measured in units of pH which are a logarithmic scale measure of the concentration of free hydrogen (H+) ions in solution. Values at the low end of the pH scale (1-7) represent extreme to neutral acidity, while values at the high end of the pH scale (7-14) are a measure of the neutral to extreme alkalinity of water.
The pH guideline for the protection of aquatic ecosystems was used for the exceedance assessment. Guideline boundaries varied from State to State (see below) reflecting the variability of surface water conditions and management objectives.
The two pie charts present pH results aggregated from individual monitoring station to represent the pH status of the entire basin. They show the relative proportion of the basin area that was classified as having good, fair or poor water quality in terms of pH guideline exceedances and the relative proportion of the basin area that was assessed as having increasing, decreasing or static pH trends.
The proportion of the basin for which no data was available is also presented and provides an indication of the monitoring coverage of the basin for pH.
Exceedance
Nutrients
Trend - total nitrogen
Trend - total phosphorus
There are a number of nutrients that effect the quality of surface waters. These include nitrogen, phosphorous and organic carbon. These nutrients can occur in a range of chemical forms. Two measure of nutrient concentration in surface waters, total nitrogen and total phosphorus were assessed as part of the Audit. Total Nitrogen - is a measure that sums the concentration of the major forms of nitrogen including ammonia, organic nitrogen, nitrate and nitrite. Total phosphorus - is a measure that sums the concentration of all forms of phosphorus in the water column including dissolved forms, insoluble particulate forms and phosphorus already incorporated in phytoplankton. Both variables require laboratory analysis of samples collected in the field for accurate measurement. While national guidelines for both total phosphorus and total nitrogen are established in units of micro grams per litre (m gL-1), State and Territory guideline specification and operational practice utilise units of milligrams per litre (mgL-1).
The total nitrogen and total phosphorus guidelines for the protection of aquatic ecosystems were used for the exceedance assessments. Guideline boundaries varied from State to State (see below) reflecting the variability of surface water conditions and management objectives.
The four pie charts present both total nitrogen and total phosphorus results aggregated from individual monitoring stations to represent the total nitrogen and total phosphorus status of the entire basin. They show the relative proportion of the basin area that was classified as having good, fair or poor water quality in terms of total nitrogen or total phosphorus guideline exceedances and the relative proportion of the basin area that was assessed as having increasing, decreasing or static total nitrogen or total phosphorus trends.
The proportion of the basin for which no data was available is also presented and provides an indication of the monitoring coverage of the basin for both nutrients.
Exceedance - total nitrogen
Exceedance - total phosphorus
Turbidity
Trend
Turbidity is a measure of the clarity, 'dirtiness' or light scattering/absorbing capacity of water, which is roughly proportional to the type and concentration of suspended matter. It is therefore commonly used as an indicator of the amount of suspended solids in the water column. Turbidity is usually measured in Nephelometric Turbidity Units (NTU), which provide a measure of the capacity of light to penetrate through water. Total suspended solids (TSS) measured in milligrams per litre (mgL-1) is also used as a less accurate measure of turbidity in some instances and by some States (i.e., WA) although it is recognised that non-solid or dissolved substances within water can also affect turbidity.
The turbidity guideline for the protection of aquatic ecosystems was used for the exceedance assessment. Guideline boundaries varied from State to State (see below) reflecting the variability of surface water conditions and management objectives.
The two pie charts present turbidity results aggregated from individual monitoring stations to represent the turbidity status of the entire basin. They show the relative proportion of the basin area that was classified as having good, fair or poor water quality in terms of turbidity guideline exceedances and the relative proportion of the basin area that was assessed as having increasing, decreasing or static turbidity trends.
The proportion of the basin for which no data was available is also presented and provides an indication of the monitoring coverage of the basin for turbidity.
Exceedance
Faecal coliforms
No Faecal Coliforms information exists for this basin
Blue-green algae
No Blue-Green Algae information exists for this basin
Further Information
Key
Links to an another web site
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