1.5.2 Water quality

Summary

Poor water quality due to high salt concentrations has been a considerable issue in parts of the Hunter river basin. This is largely a consequence of geological conditions, but may have been exacerbated in the Hunter River by discharges of saline groundwater from mining operations and rising groundwater levels from past land clearing. The Hunter River Salinity Trading Scheme (HRSTS) was introduced in 1995 to minimise the impact of saline water discharges from industry.

This section reports stream salinity from monitoring throughout the Hunter river basin, with particular focus on three gauging stations on the Hunter Regulated River (Denman, Glennies Creek and Singleton). Salinity levels are typically fresh in the north-east of the river basin, which has important water supply catchments. Higher salinities occur in Wybong and Goulburn rivers and around Lake Liddell. Along the Hunter Regulated River, mean electrical conductivities between 1995 and 2013 varied from around 600 µS/cm at Denman to 750 µS/cm at Glennies Creek to 640 µS/cm at Singleton. All sites exhibit high variability, particularly at low flows when baseflow discharges dominate the streamflow response.

The groundwater quality data available for the Hunter subregion were generally poor and difficult to draw firm conclusions from. Analysis of the available salinity data indicated that salinity in the coastal sands aquifer was on average lower than in alluvial and fractured rock aquifers. The results are not statistically significant as they are based on five samples only. There are large ranges in salinity in the alluvial (21 to 14,500 µS/cm) and fractured rock aquifers (29 to 48,600 µS/cm) but major errors were found in the dataset that undermine confidence in these ranges. For most samples, the hydrostratigraphic unit from which they were obtained was not known. Possibilities for beneficial use of water are provided based on median electrical conductivity values.

Some trace element data are presented for groundwater, but it is difficult to provide meaningful interpretation given the limited number of samples for some elements and lack of information about the water sources sampled and origins of the trace elements.