The Brigalow Catchment Study: The effects of land clearing in the Brigalow bioregion of Australia (1965 - current)

Level 1 General description


The purpose of the Brigalow Catchment Study was to determine the impact of land use change (Brigalow vegetation to cropping and grazing) on hydrology.

Methods (brief)

Rainfall and runoff data were obtained over 17 years to define the hydrology of 3 adjoining catchments. Following the initial monitoring period, 2 of the 3 catchments were cleared with 1 of them being used for cropping and the other used for grazing. The catchments were then monitored for water balance, resource condition, productivity, rainfall and runoff.

Thornton et al. (2007) used several analytical techniques to confirm that land use has an influence on runoff.

Radford et al. (2007) monitored the decline in productivity levels of developed brigalow land over 23 years post clearing.

Titmarsh et al. (2009) collected nitrogen and phosphorous levels in rainfall and runoff samples over three years for thirty-one plots (<10 ha in size), each with a particular land use and soil type combination and from three sets of larger nested catchments (3 - 200000 ha) with mixed land use/soils in the Queensland Murray Darling Basin (QMDB).

Key findings (brief)

  • Thornton et al. (2007) found total annual runoff increased to 11% and 9% of annual rainfall in the cropping catchment and pasture catchment respectively (average annual runoff in the virgin state is 5% of annual rainfall).
  • Radford et al. (2007) observed a decline in crop production per year by 20% between 2 successive 10-year periods.
  • Grain yield from 14 winter crops without added nutrients declined significantly in 20 years from 2.9 to 1.1 t/ha/year on the upper-slope clay soil (92 kg/ha/year) and from 2.4 to 0.6 t/ha/year on the Sodosol (88 kg/ha/year).
  • The grazed site had an initial pasture dry matter on offer of 8 t/ha which halved 3 years after clearing, and a decline in cattle live weight gain of 4 kg/ha/year was observed over an 8-year period with constant stocking of 0.59 head/ha.
  • Thornton et al. (2012) found that subsequent reductions in soil chloride under cropping were only significant in the upper clay soil, while under pasture, no further significant change occurred.
  • Chloride mass balance analysis indicates deep drainage of 0.17 mm/year for clay soils and 0.26 mm/year for Sodosols under virgin brigalow scrub. These drainage rates increased during the land development phase to 59 mm/year for C2 and 32 mm/year for C3.
  • Titmarsh et al. (2009) found that the export of N and P from all the single land use/soil type catchments was positively correlated with soil fertility and increased as land use intensity increased. Nutrient export rates for the nested catchments did not correlate well to land use. Average rainfall TN and TP concentrations were 0.38 and 0.04 mg/L respectively.

Table 1: Summary of Observed Average Annual Runoff and Sediment Loss for Brigalow catchment study. Howleaky simulation results presented for trial period (Freebairn and Cutajar 2012)

Description of Management system







Sediment loss




Sediment loss


Brigalow scrub (C1)



0.3 –0.33



Opportunity cropping (C2)



0.8 - 3.2



Buffel grass pasture (C3)



0.17 - 0.28





The site is located at 24.81o S and 149.80o E in the Brigalow Research Station, south-west of Rockhampton.

Related studies

  1. Arnold S, Thornton C, and Baumgartl T. (2012). Ecohydrological feedback as a land restoration tool in the semi-arid Brigalow Belt, Qld, Australia. Agriculture, Ecosystems and Environment. Article in Press.

Further Access

Further information on the Brigalow catchment study may be available through the DSITIA www and related databases


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