1.1.6.2 Bremer river basin, Warrill Creek and Purga Creek basins

The Bremer River and Warrill Creek are deeply incised into the Main Range Volcanics in their headwaters and form thin and comparatively narrow alluvial systems that overlie the Walloon Coal Measures throughout the rest of their river basins. The Purga Creek alluvium directly overlies the Walloon Coal Measures or other Clarence-Moreton bedrock formations throughout its entire course. Pearce et al. (2007a) noted that Purga Creek is characterised by higher salinities than the Bremer River and Warrill Creek, and they have also observed that the Purga Creek and the Walloon Coal Measures have similar hydrochemistries. This was also independently confirmed by a report from the Bremer Catchment Association (2005), in which high electrical conductivities of approximately 6500 µS/cm were measured for Purga Creek in comparison to the much lower electrical conductivities of less than 1000 µS/cm measured for the Bremer River and the Warrill Creek. Pearce et al. (2007a) indicated that this was probably due to a strong contribution of baseflow from the Walloon Coal Measures to Purga Creek, whereas interaction between the Main Range Volcanics and Bremer River and Warrill Creek generated fresher surface waters. A more detailed assessment of salinity issues in Purga Creek is currently being conducted (R Shaw, 2013, pers. comm.).