Dataset: Groundwater Zone of Impact for the Namoi subregion



This dataset was created within the Bioregional Assessment Programme. Data has not been derived from any source datasets. Metadata has been compiled by the Bioregional Assessment Programme.

The Zone of Impact (ZOI) is derived from the groundwater management units, mining development leases and/or coal seam gas (CSG) tenements, and directional flows of groundwater (Barrett et al., 2013). The process of defining the ZOI is undertaken via consideration of the vertical and horizontal proximity and scale of groundwater connectivity pathways and potential for depressurisation or dewatering.


The purpose of the ZOI is to provide a first step in the process of determining whether a water-related link is possible between coal resource development and the assets. It is intended to be a realistic yet inclusive estimate of the land surface area where potential impacts might occur. As the model-data analysis, impact analysis and risk analysis components of a BA are completed it will be possible to more closely characterise and quantify impacts in terms of their extent and their likelihood.

Dataset History

Schlumberger Scenario 3 with Santosh's buffer: GroundwaterZoneofImapctMaps_Schlumberger1.pdf

Damian Barrett's polygon with justification: DamiansPolygon.pdf

Jim Kellet's Lower Namoi ZOI: Lower Namoi ZOI.pdf


Development (see GroundwaterZoneofImapctMaps_Schlumberger1.pdf):

Expert opinion by Santosh Aryal (CSIRO). Schlumberger have prepared model scenarios and run their groundwater model. Scenario 3 is the most likely development scenario and is published in their 2012 groundwater model report which is archived at:

Lower Namoi groundwater impacts (see Lower Namoi ZOI.pdf):

Expert opinion by Jim Kellet (GA). For the Cainozoic sediments in the lower Namoi the impact boundary would extend across the entire area of occurrence of the Namoi alluvium defined by the Lower Namoi WSP boundary in Smithson (2009) whcih can be found at: An ultra-conservative boundary would be the entire area between two dividing streamlines in the alluvium enveloping the Namoi alluvium, the southern one extending NW from the common corner of the Gilgandra and Walgett 1:250 000 sheets and the northern one approximately collinear with the northern WSP boundary. These same boundaries (the ultra-conservative ones) would also be an appropriate impact boundary for the underlying GAB sequence. The rationale behind the choice in both hydrogeological systems is that there is no groundwater flow radially outwards from these boundaries. The recommended ZOI boundary for the Lower Namoi is almost identical to the Lower Namoi alluvium defined in the Namoi Water Sharing Plan. The background heads are the watertable contours plotted on 1:250 000 maps and indicate some flow into the zone but no groundwater flow out of it. The no outflow condition is the rationale for choosing this particular boundary.

Expert scientist view (DamiansPolygon.pdf)

Damian Barrett (CSIRO). Keep lower Namoi alluvium as may be impacted. Stay west of Hunter-Mooki Fault - elsewhere use catchment boundaries.

Dataset Citation

Bioregional Assessment Programme (2013) Groundwater Zone of Impact for the Namoi subregion. Bioregional Assessment Source Dataset. Viewed 11 December 2018,

General Information