This product summarises surface water quality information in the Gloucester subregion where there are two main sources of surface water quality data. This includes water quality monitored by the NSW Office of Water , and surface water sampled and monitored by coal mining companies (Gilbert and Associates, 2010; SRK, 2010; . Two water quality indicators included in this report are electrical conductivity (EC), an indication of salinity, and pH.
There is no long-term water quality monitoring programme in the Gloucester river basin. Water quality measurements were mainly conducted on the Avon river basin where there exists coal mining and coal seam gas exploration. The NSW Office of Water commenced a surface water quality monitoring program in the Gloucester valley in November 2013 . The program initially included basic water quality analyses, but was expanded in July 2014. There are two monitoring sites on the Avon River. At the upper site (upstream of Stratford) median field EC and pH readings are 351 µS/cm and 6.76, respectively. At the downstream site (near Gloucester) median EC and pH readings are 2012 µS/cm and 5.86, showing an increasing trend in electrical conductivity and a decreasing trend in pH with distance down the catchment.
Other reported EC values on the Avon River are less than 500 µS/cm. The EC and pH were intermittently measured between 1993 and 2009 on the Avon River, Avondale Creek and Dog Trap Creek . Measured ECs vary from 100 to 500 µS/cm and pH is near neutral to slightly alkaline. The EC values were found to be well related with rainfall, with a reduction in EC following rainfall and an increase in EC when flow reduces and baseflow increases. Another water quality sampling programme was undertaken in April 2011 at three monitoring locations on the Avon River . Salinity at the time of sampling was fresh with EC values less than 324 µS/cm and showing a slight increase in a downstream direction. The pH is near neutral, with a pH value varying from 6.6 to 7.4.
For the southern part of the Gloucester subregion, surface water sampling was intermittently undertaken by Gloucester Coal Ltd on Karuah River and Mammy Johnsons River from 2002 to 2009 . The EC during the observation period was less than 600 µS/cm for the Mammy Johnsons River, and less than 400 µS/cm for the Karuah River; pH for both rivers shows large variation, varying from 6.3 to 8.5.
The NSW Office of Water maintains a long term water quality data set for the Karuah River at Booral (gauge ID: 209003) located downstream of the assessment area. From 2007 to 2014, monthly EC readings ranged from 96 to 346 µS/cm with a median of 225 µS/cm. Values of pH ranged from 6.3 to 7.6 with a median of 6.99.
There is a lack of long-term consistent monitoring of EC and pH for the Gloucester river basin. As a result, the capacity to fully understand what baseline water quality should be for this area is limited.
The NSW Office of Water monitors ambient river water quality at strategic locations and maintains long term data sets for sites across NSW. Attributes currently monitored represent general water quality condition and are most likely to demonstrate change over time from broad scale implementation of natural resource management. The surface water quality data gaps in the Gloucester valley are currently being addressed by NSW Office of Water monitoring programs.