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RESEARCH ARTICLE
Contents Vol 48(4)

Temporal and spatial patterns of salinity in a catchment of the central wheatbelt of Western Australia

M. J. Robertson A D , R. J. George B , M. H. O’Connor A , W. Dawes C , Y. M. Oliver A and G. P. Raper B
+ Author Affiliations
- Author Affiliations

A CSIRO Sustainable Ecosystems, Private Bag 5, PO Wembley, WA 6913, Australia.

B Department of Agriculture and Food WA, PO Box 1231, Bunbury, WA 6231, Australia.

C CSIRO Land and Water, Floreat, WA, Australia.

D Corresponding author. Email: Michael.Robertson@csiro.au

Australian Journal of Soil Research 48(4) 326-336 https://doi.org/10.1071/SR09126
Submitted: 14 July 2009  Accepted: 15 January 2010   Published: 16 June 2010

Abstract

Many estimates have been made of the future likely extent of salinity at regional and national scales in Australia; however, there are few detailed studies of changes in temporal and spatial patterns at catchment scale. This study was conducted in the Wallatin and O’Brien catchments in the low–medium rainfall zone of the central wheatbelt of Western Australia, where we examined the spatial trends in saline land over the last 18 years and related these to the likely rate and extent of future salinisation.

The analysis showed that: (1) salinity has continued to expand post-1999 in landscape positions where there has been watertable rise and also in areas now at equilibrium even though rainfall has been below average; (2) increases in the area of salinity are still dominated by increases in the valley floor but there is now the emergence of many small, isolated outbreaks on the adjacent slopes; (3) widely available satellite-derived salinity maps (LandMonitor) derived in 1998 provide a reliable base-line for saline mapping but now underestimate the area of salt-affected land by 60%; (4) the trend in watertable levels and time since clearing and interactions with proximity to uncleared native vegetation provide reliable predictors of salinity risk; (5) episodic rainfall in areas of shallow watertables is proposed as a significant cause of the expansion in observed salinisation, even though some of this may be transient.

These results are discussed in terms of management options for farmers and the likely long-term outlook for expansion of salinity in the catchment.


Acknowledgments

This research was supported by the Grains Research and Development Corporation, CSIRO’s Water for Healthy Country Flagship, and the Catchment Demonstration Initiative. Thanks to Fay Lewis for data from hydro-geological analysis and many stimulating discussions that influenced this paper. Martin Wells of Land Assessment Pty Ltd provided the soil map for Wallatin–O’Brien. Input from the landholders of Wallatin–O’Brien in mapping salinity is gratefully acknowledged. Hamish Cresswell provided helpful comments on an early draft of the paper.


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