WA salt problem exaggerated

17 Nov, 2004 10:00 PM

CSIRO investigators believe the extent of WA's salinity problem is closer to half the figure commonly reported.

CSIRO regional co-ordinator Don McFarlane said he and his research team used the highly-accurate Land Monitor system of digital terrain models to produce a figure of about one million hectares of land directly affected by salinity in WA.

This contrasted with the figure of 1.8mha affected as of 1994 - produced by aerial photography and geophysical methods - that formed the basis for planning in WA's Salinity Action Plan of 1996 and Salinity Strategy of 2000.

"Early estimates were done by mapping a few catchments, recording the level of salinity in those areas and saying that if this was similar to what it was in other catchments, then this was what it will be for the state," he said.

Mr McFarlane said Land Monitor was a far more accurate recording system and did not extrapolate results for other catchments.

It produced precise digital elevation models, mapped and monitored the changes in area of salt-affected land from 1988, and predicted areas at risk of future salinisation.

"The other big thing is that from 1989 to 1996, we've found that salinity really only increased 14,000ha per annum, which is a lot less than other estimates," he said.

There were positive implications of these results.

"The current and predicted future extent of salinity is useful to help decide how much resources agencies and landowners commit to saving assets that may be at risk, and when they should commit these resources," he said.

"If the problem is that much smaller, it gives us substantially more time to develop better farming systems, engineering options and so on. We don't need to panic or think the game's up or anything like that."

But he warned salinity was still a huge problem and there was no room for complacency.

The area of WA farmland directly affected by salinity according to the Land Monitor system is 820,000ha, which was similar to the 933,000ha level reported by farmers in a 2002 Australian Bureau of Statistics survey.

The area of farmland at risk of future salinity is 4.4mha, while the total amount of land at risk is 5.4mha.

Mr McFarlane said these figures were also smaller than previous estimates, while those areas at risk were potentially 50 to 100 years away from turning saline.

Reduced rainfall in the past 25 years may also have reduced the final area likely to be impacted by salinity and the rate it is spreading per year.

"All the indicators are that salt really goes berserk during those wet periods, so if you're in a dry area and not catching the tail-ends of those cyclones, then it is likely that salinity will be stabilising or in some cases even decreasing," he said.

He said further refinements and updates of Land Monitor methodology and area estimates were required, as it was eight years since the last estimate and saline areas may have increased by a further 100,000ha or 0.3pc.

Mr McFarlane's team received a CSIRO chairman's medal for their work with the Land Monitor system.



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