Oral Presentation Australasian Groundwater Conference 2017

Remapping and validation of gaining steams in the Surat Basin – an integral part of understanding impacts on environmental values (#38)

Jit Khor 1 , Steve Flook 1
  1. Office of Groundwater Impact Assessment, Brisbane, QLD, Australia

Increased confidence in the mapping of gaining streams in the Surat Basin is essential for improving conceptual understanding of surface-groundwater interaction and for assessing impacts from groundwater development on associated environmental values. The Office of Groundwater Impact Assessment (OGIA) has initiated a project to remap gaining streams in the Surat Basin using new data generated since the last assessment in 2005.

OGIA is responsible for the assessment of cumulative groundwater impacts from petroleum and gas (P&G) activities in the Surat Cumulative Management Area (CMA). OGIA’s assessment includes regional groundwater flow modelling and the development of monitoring requirements for aquifers and groundwater dependent ecosystems (GDEs) – specifically, springs and gaining section of streams (‘watercourse springs’). In the Surat Basin, gaining streams often result from the dissection of an outcropping aquifer by surface water flows, resulting in the watertable being intersected by the streambed.

At a regional scale, this project uses multiple data sources to identify areas where gaining streams potentially exist. This included the development of a methodology to generate watertable mapping by integrating bore data and a digital elevation model, and assessing other new datasets such as the Queensland GDE mapping. The output from this process is a revised map of potentially gaining reaches in the Surat Basin.

A risk based approach was applied to identify sites for field validation. Outputs from impact assessment were used to prioritise sites for field investigation. Surface water and groundwater data was collected including groundwater pressure, major ion chemistry, isotope analysis (222Rn) and field observations at two field sites.

The outcomes from this project improve the conceptual understanding of surface-groundwater connectivity in the Surat Basin and provides a basis for the establishment of appropriate management strategies for gaining streams in the next iteration of the Surat UWIR. 

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