1.1.5.2 Surface water quality

The surface water quality indicators given by the percentage of samples exceeding Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines (ANZECC and ARMCANZ, 2000) for turbidity and total phosphorus for protecting the aquatic ecosystem for 2007 to 2008 at four locations within the subregion and at eight locations outside of the subregion are shown in Table 14 . The guideline values for total phosphorus are 0.02 mg/L for upland sites (> 150 m above mean sea level) and 0.05 mg/L for lowland sites. The corresponding values for turbidity are 25 and 50 nephelometric turbidity units (NTU), respectively. Table 14 shows that all sample locations in the Macquarie river basin, except at Turon River, overwhelmingly exceed the limit for total phosphorus. Within the subregion, most samples meet the turbidity guidelines except in the Talbragar River.

The NSW Office of Water monitors ambient river water quality at strategic locations and maintains long-term datasets for sites across the Central West. Attributes currently monitored represent general water quality condition and are most likely to demonstrate change over time from a broad scale implementation of natural resource management perspective (for example, turbidity, total nitrogen, total phosphorus, electrical conductivity, pH and water temperature) (W Mawhinney, 2014, pers. comm.).

Not all monitoring stations in the region record all water quality indicators. Table 15 summarises water quality assessments for the Macquarie-Bogan and Castlereagh river basins at 17 sites and one site, respectively. Except for turbidity and pH, all the water quality indicators listed in the table were rated ‘poor’ to ‘very poor’ (DSEWPaC, 2011). Note that data in Table 14 and Table 15 were assessed against the ANZECC water quality guidelines and not against the Basin Plan water quality targets which will be used in the future (W Mawhinney, 2014, pers. comm.).

Chapter 9 of the Basin Plan describes water quality and salinity management plan including types and 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.

Data from NSW Government (2013) show that the median of mean monthly daily electrical conductivities (EC) at a station in the Castlereagh river basin (Castlereagh River at Hidden Valley, 420017) for 2002 to 2013 is 335 mS/cm and the daily mean water temperature ranges from 5 to 30°C. For a station in the Macquarie river basin (Macquarie River at Carinda, 421012) the median of mean monthly EC is 553 mS/cm and the mean daily temperature ranges from 9 to 30°C. Trend analyses for EC, temperature and turbidity were also done, however data confidence for all sites for all indicators was considered to be low (NSW Government, 2010).

Table 14 Percentage of samples that exceeded Australian and New Zealand Environment and Conservation Council guidelines for total phosphorus and turbidity at different locations within and outside of (in italics) the Central West subregion

Source data: NSW Government (2010)

Table 15 Water quality assessment for Macquarie-Bogan and Castlereagh rivers

Source data: DSEWPaC (2011)

TN total nitrogen; TP total phosphorous