Richmond river basin

Although a substantial amount of work has been conducted on different aspects of surface – groundwater interaction within the Richmond river basin (e.g. Drury, 1982; Sammut et al., 1996; Brodie et al., 2007, 2009; Sundaram et al., 2009; Santos and Eyre, 2011; Santos et al., 2011; Davis, 2012; Atkins et al., 2013), no comprehensive basin-wide assessment has been conducted. Brodie et al. (2007) compared different techniques and their applicability to assess surface – groundwater interactions in the Richmond river basin. They concluded that within the Richmond river basin, the groundwater component of baseflow varies substantially depending on the aquifer system. Their study showed that towards the north, the aquifers of the Alstonville Basalt, as well as North Coast Fractured Rocks (which are composed of fractured basalts), can maintain perennial streams. In the southern part of the river basin, the geology changes from the fractured rocks of the basalts to the lower permeability sedimentary sequences of the Clarence-Moreton Basin. Brodie et al. (2007) explained that Q90 flow rates (the flow rate exceeded 90% of the time) observed in creeks associated with these different hydrostratigraphic units and normalised for area vary by over two orders of magnitude, thus indicating a significantly higher baseflow volume from basalts to streams.

Davis (2012) analysed water chemistry and isotopes for several tributaries to the Richmond River. The presence of 222Rn in surface waters confirmed the presence of groundwater; however, the study highlighted the need to conduct more comprehensive time series analysis of environmental tracers to capture spatial and seasonal or longer-term variability.

Coastal sand aquifers, such as the Woodburn Sands (located on the eastern coastline in the Richmond river basin), have a strong degree of connectivity to streams and wetlands – including the Tuckean Swamp (Drury, 1982; Metgasco, 2007). Drury (1982) suggested that groundwater infiltrates through floodplain deposits and discharges into the Tuckean Swamp as well as the Richmond River; however, the Tuckean Swamp may recharge underlying aquifers during drought conditions.

Santos et al. (2011) analysed the times-series of surface water and groundwater chemistry in the Richmond river basin. They suggested that seepage from shallow groundwater is the major pathway that releases metals such as Al and Mn (from coastal acid sulfate soils) to the Richmond River.

Recent mapping of groundwater-dependant ecosystems in the coastal parts of the Richmond river basin has identified wetland clusters and their relationship to geology and landform and the likely water source (NSW Office of Water, 2013).

Last updated:
8 January 2018
Thumbnail images of the Clarence-Moreton bioregion

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