Australian Natural Resources Atlas

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Water resources - Quality - Queensland

Location map of Basin Condamine-Culgoa Rivers

Basin: Condamine-Culgoa Rivers

Surface water quality in Condamine-Culgoa Rivers

Copyright Context map of Basin Condamine-Culgoa Rivers

Attributes for which exceedance analyses could be determined:

Salinity, pH, Total Phosphorus, Total Nitrogen, Turbidity

Attributes for which trend analyses could be determined:

Salinity, pH, Total Phosphorus, Total Nitrogen, Turbidity

The Condamine-Culgoa Rivers basin is located in the Murray-Darling drainage division. Set inland, the topography is primarily flat with wide alluvial floodplains. Streams in much of this region are typical of many Australian inland waters. They are slow flowing and meandering, with long periods of low or zero flows during which the streams can become a series of waterholes. There are a number of storages and weirs, as well as many off-stream ring tanks throughout the region and some flows are highly regulated. The eastern catchment contains fertile cropping areas including the Darling Downs. Further west, grazing predominates but there are a number of important irrigation areas, farmed mainly for cotton.

Data for the exceedance analysis were collected from eight sites, which are located in the Condamine-Balonne River, and Sandy and Iron Pot Creeks. Together, these sites represent approximately 10% of the basin. For the trend analysis, data were collected from ten sites, located in the Condamine-Balonne River, and Swan, Emu, Oakey and Hodgson Creeks. Together, these sites represent 41% of the basin. Given the poor coverage of this basin, a firm assessment of the basin's condition cannot be made.

The exceedance analysis indicated that salinity levels throughout the catchment are low. However, increasing surface water conductivity levels were detected in the upper catchment. This is thought to be associated with land-clearing and agricultural activity on soils with naturally high salt content.

Generally, the waters of the Condamine-Balonne exhibited high levels of turbidity, exceeding ANZECC (1992) and NHMRC (1996) targets. It is thought that the nature of the local soils may be the main cause for these turbid conditions as the highest turbidities actually occur in the less intensively cultivated lower reaches of the catchment (DNR & EPA, 1998). However, the trend analysis indicates that turbidity levels are increasing in the middle catchment, suggesting that the removal of native vegetation and associated cropping and cattle grazing may exacerbate erosion in the basin.

From the limited data available, TP concentrations were found to be extremely high in the middle catchment. This is thought to be a result from a combination of factors, including high sediment concentrations in the water and point discharges, such as treated sewerage, septic and animal husbandry effluent discharges (DNR & EPA, 1998).

Due to unsystematic monitoring of TN in the catchment, TN data were not available for this study. However, given the intensity of cultivation activities in the catchment, particularly in the middle to upper catchment, it is likely that surface water's TN levels are elevated.

pH levels were found to be within ANZECC (1992) and NHMRC (1996) targets throughout the monitored catchment.

Monitoring StationSalinity - Electrical conductivityTotal nitrogen Total phosphorus Turbidity pHBlue Green Algae
ExceedTrendExceedTrendExceedTrendExceedTrendExceedTrendExceedTrend
422308CNo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo TrendNo DataNo Data
422333AGoodNo TrendNo DataNo DataPoorNo DataPoorIncreasing TrendGoodNo TrendNo DataNo Data
422352ANo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo DataNo DataNo DataNo DataNo Data
422350ANo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo TrendNo DataNo Data
422213ANo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo TrendNo DataNo Data
422316AGoodNo TrendNo DataNo DataPoorNo DataPoorNo TrendGoodNo TrendNo DataNo Data
4222048GoodNo DataNo DataNo DataNo DataNo DataPoorNo DataGoodNo DataNo DataNo Data
422355AGoodNo DataNo DataNo DataPoorNo DataPoorNo DataGoodNo DataNo DataNo Data
422306ANo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo Data
422310CGoodNo TrendNo DataNo DataFairNo DataPoorNo TrendGoodNo TrendNo DataNo Data
4223055No DataNo DataNo DataNo DataGoodNo DataNo DataNo DataNo DataNo DataNo DataNo Data
422313BNo DataNo TrendNo DataNo DataNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo Data
422356AGoodNo DataNo DataNo DataGoodNo DataPoorNo DataGoodNo DataNo DataNo Data
422357AGoodNo DataNo DataNo DataNo DataNo DataPoorNo DataGoodNo DataNo DataNo Data
422394ANo DataIncreasing TrendNo DataNo DataNo DataNo DataNo DataNo TrendNo DataNo TrendNo DataNo 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.

Note: some attribute information may not be available for some areas

Trend Legend

Trend chart legend

Exceedance Legend

Exceedance chart legend

Salinity

No Salinity information exists for this basin

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Surface Water pH

No pH information exists for this basin

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Nutrients

No Nutrient information exists for this basin

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Turbidity

No Surface Water Turbidity information exists for this basin

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Faecal coliforms

No Faecal Coliforms information exists for this basin

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Blue-green algae

No Blue-Green Algae information exists for this basin

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Further Information

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