1.1.5.2 Surface water quality

Queensland has a surface water quality network of about 240 stations monitoring in situ measurements using manual sampling as well as continuous water quality measurements (167 stations). These measurements generally include electrical conductivity (EC) at 25 °C, temperature, pH, turbidity, nutrients, dissolved oxygen and total alkalinity (DERM, 2012b). The manual water sampling frequency for all stations in the subregion is four times a year, except in the Oakey Creek (tributary of the Condamine River) which is sampled 12 times a year (DERM, 2012b).

Chapter 9 of the Murray–Darling Basin Plan outlines water quality and salinity management issues, including key causes of water quality degradation in the Basin (MDBA, 2012). It also contains water quality targets for different water use purposes such as irrigation, fresh water-dependent ecosystems for different ecosystem types and recreational water.

1.1.5.2.1 Condamine-Balonne river basin

Water quality data are gathered in the Condamine-Balonne river basin for a range of water quality markers including total nitrogen, total phosphorus, total suspended solids and many other chemicals, such as cadmium, copper, the herbicides Atrazine and Diuron, and the insecticide Dieldrin (DERM, 2011). In the upper Condamine river basin nutrient levels were found to be generally within the guidelines at the nutrient monitoring sites. EC was relatively high in the upstream parts of the Condamine River. The EC measured on the Condamine River at Chinchilla Weir showed values ranging from 800 µS/cm during low flows to 100 to 180 µS/cm during high flows. These results indicate that the Condamine River is relatively saline compared to other rivers in Queensland. Nutrient and turbidity data are generally deficient along the Condamine-Balonne River (DERM, 2011).

An ambient surface water quality summary report by the Department of Environment and Resource Management only reports the direction of water quality trends due to data limitations in most Queensland catchments; they note that reporting on magnitude would not be sufficiently reliable or meaningful (DERM, 2011, p.10). EC and turbidity trends in some of the Condamine-Balonne river basin catchments are summarised in Table 11. Trend data for other water quality indicators are unavailable.

Table 11 Electrical conductivity and turbidity trends in the Condamine-Balonne river basin

^awith available data Source data: DERM (2011)

1.1.5.2.2 Moonie river basin

The two streamflow gauging stations in the Moonie river basin (at Nindigully and Fenton) have high concentrations of total nitrogen, which requires management action (DERM, 2011). However, no trends for EC and turbidity are apparent.

1.1.5.2.3 Border Rivers river basin

Sites in Border Rivers river basin in Queensland (not all within the subregion) are monitored on a monthly basis by the NSW Office of Water on behalf of Dumaresq Barwon Border Rivers Commission for electrical conductivity, nutrients, turbidity, total suspended solids and water temperature. Summary statics of the samples are reported for electrical conductivity, total phosphorus, total nitrogen and turbidity (DBBRC, 2012a). DBBRC (2012b) reports that median salinity level in the Border Rivers basin are below the low salinity guidelines for irrigation water. Macintyre Brook however had the salinity level above the guidelines for protection of aquatic ecosystems in upland streams. Turbidity levels in the Border Rivers river basin showed a gradual increase downstream along the waterway towards Mungindi. The Weir River is the most turbid and most nutrient rich (DBBRC, 2012b).

The DERM (2011) however reports that the streamflow gauging station in the Weir River has insufficient water quality data to assess levels and trends of EC, nitrogen, phosphorus and turbidity. In Macintyre Brook, EC is within the guidelines, while data for nitrogen, phosphorus and turbidity are insufficient for meaningful assessment (DERM, 2011).