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Goulburn-Broken Catchment, Australia

Main Contributors:

Reinette (Oonsie) Biggs

Other Contributors:

Summary

Around 85% of the native woodland and forest cover has been removed from the mid catchment of the Goulburn-Broken, and 98% from the lower catchment (GBCMA 2003). Anderies et al. (2006b) estimate that the cover of woody vegetation was reduced to below the threshold level needed to maintain the water table below the surface about a decade after clearing began. This threshold is estimated at about 80% vegetation cover in the mid catchment (groundwater in the upper catchment appears not to be connected to water tables in the mid and lower catchment). As water tables rise in response to the reduced vegetation cover, there is a critical threshold at around 2 m below the surface (depending on soil texture). When the water table rises above this, capillary action draws water to the surface. The height of the water table determines the area salinized because of topographic variation, so area salinized and water-table depth are treated as a single threshold. Because of a strong hysteresis effect (tree roots do not function well in saturated soil, so it takes more trees than in unsaturated soil to achieve the same amount of transpiration), more than 80% of the catchment needs to be revegetated to change the trajectory of the system such that the equilibrium water-table depth is below the root zone. As this would affect large areas of dryland farms, pumping is needed in addition to revegetation—the less revegetation, the more pumping (see Anderies et al. 2006b). A constraint is the large volumes of saline water produced. Almost twice as much saline water needs to be pumped if there is no revegetation, which would violate the current salt discharge cap. Revegetation and pumping are both costly. Extracted from Walker et al 2009.

Type of regime shift

Ecosystem type

  • Agro-ecosystems

Land uses

  • Large-scale commercial crop cultivation
  • Intensive livestock production (eg feedlots, dairies)

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Australia & New Zealand

Region

  • Murray-Darling Basin

Countries

  • Australia

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Key References

  1. Walker, B. H., N. Abel, J. M. Anderies, and P. Ryan. 2009. Resilience, adaptability, and transformability in the Goulburn-Broken Catchment, Australia. Ecology and Society 14(1): 12. [online] URL: http://www.ecologyandsociety.org/vol14/iss1/art12/

Citation

Reinette (Oonsie) Biggs. Goulburn-Broken Catchment, Australia. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2012-11-10 14:25:51 GMT.
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