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Surface Water - Groundwater Interactions in the Lower Fitzroy River, Western Australia

Harrington, Glenn, Stelfox, Louise, Gardner, Payton, Davies, Phil, Doble, Rebecca and Cook, Peter (2011). Surface Water - Groundwater Interactions in the Lower Fitzroy River, Western Australia<br />. Australia: CSIRO.

Document type: Research Report
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Author Harrington, Glenn
Stelfox, Louise
Gardner, Payton
Davies, Phil
Doble, Rebecca
Cook, Peter
Title of Report Surface Water - Groundwater Interactions in the Lower Fitzroy River, Western Australia
Publication Date 2011
ISBN Water for a Healthy Country Flagship Report series ISSN: 1835-095X   (check CDU catalogue open catalogue search in new window)
Publisher CSIRO
Place of Publication Australia
Total Pages 62
Field of Research 300800 Environmental Sciences
Abstract EXECUTIVE SUMMARY

The water resources of the lower Fitzroy River catchment in the Kimberley region of north-west Western Australia are continuing to present both opportunities and impediments for future irrigation development, mining activities and municipal water supply to southern parts of the State. The recent CSIRO Northern Australia Sustainable Yields (NASY) project revealed that the groundwater and surface water resources of this catchment, and many others across northern Australia, lack the historical monitoring data and fundamental technical understanding required to undertake quantitative water assessments and therefore establish sustainable water management policies. In particular, there is a dearth of information and knowledge of groundwater controls on dry season flows in the Fitzroy River. This report presents a synthesis of preliminary research projects that have aimed at starting to address these knowledge gaps. It includes work undertaken by CSIRO as part of the Tropical Rivers and Coastal Knowledge (TRaCK) program, as well as a project in which CSIRO collaborated with WA Department of Water under the Raising National Water Standards program of the National Water Commission, and finally work undertaken by CSIRO as an extension to NASY.

This suite of projects has used contemporary hydrogeological mapping techniques and water bore drilling, in combination with groundwater and river sampling for both routine and novel environmental chemistry analyses. A transect of nine new monitoring bores was installed on Noonkanbah Station in October 2009 to facilitate near-river groundwater sampling and enable monitoring of groundwater level responses to wet season flood flows and recession. Groundwater samples from these shallow bores, and nine other regional bores completed in the different geologies of the Canning Basin, were analysed for major ion chemistry, stable hydrogen and oxygen isotopes of water, radon-222, noble gases (particularly helium-4), chlorofluorocarbons, carbon-14 and stable strontium isotopes. Longitudinal sampling of surface water from different reaches of the Fitzroy River was undertaken on two occasions (May 2008 and May 2010) by helicopter, and samples were analysed for a similar suite of chemical and isotopic constituents.

The main reach of the Fitzroy River on which these projects have focussed is between Jubilee Downs Station (i.e. downstream of Fitzroy Crossing) and the eastern boundary of Liveringa Station. We have identified two major zones of groundwater discharge along this reach: the first is around the confluence of the Fitzroy River with Cunningham Anabranch, and the second is between a well-known waterfall and Yungngora Community on Noonkanbah Station. Two complex discharge mechanisms have been invoked to explain chemical and isotopic data in the context of recently revised geology for these areas. In the first zone, old regional groundwater in the Liveringa Group is thought to flow westwards towards the river before being forced upwards into the alluvial aquifer, or directly into the river, as it meets the low permeability mudstones of the Noonkanbah Formation. In the second zone, even older regional groundwater from the deep Poole Sandstone aquifer is thought to discharge into the river, possibly via the alluvial aquifer, through a series of faults that transect the river. Modelling of the river chemistry profiles from May 2010 suggests the total rate of groundwater discharge over the 100 kilometre study reach is about 102 ML/day, comprising about 3.7 ML/day for the regional aquifers. The remaining discharge is sourced from local groundwater flow systems in the alluvial aquifer.

The results demonstrate a high dependence of dry season flows in the Fitzroy River on discharge from both local and regional groundwater flow systems. It is likely that future groundwater pumping  adjacent the Fitzroy River will result in a reduction to dry season flows, which in turn will have  an impact on the water level of permanent pools. The distance at which future extractive industries should be placed away from the River in order to minimise impacts to dry season flows  and permanent pools requires further research; however, it will be site specific—that is, it will  depend upon the size and pumping regime of the proposed extraction, the hydrogeological properties  of the aquifers between the river and the proposed development, and the proximity of the proposed extraction to the various groundwater discharge mechanisms identified above.
Additional Notes Results of a collaborative research initiative 2008–2011
 
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