South Perth, Western Australia
April 11, 2008
Salinity is continuing to extend
in Western Australian agricultural areas, but the
Department of Agriculture
and Food has found it is being moderated by the recent dry
period since 2000.
Spokesman Richard George said the Department’s regional
hydrologists recently analysed groundwater trends in more than
1300 bores in about 100 catchments across 19 million hectares.
“We found that groundwater levels were generally rising from
1975 until 2000, but since then both the number of bores with
rising trends and their rates of rise have decreased,
particularly in the north of the State,” Dr George said.
“In contrast, groundwater levels in the more recently cleared
areas to the west and eastern south coast near Esperance are
continuing to rise at a faster rate,” he said.
Dr George presented the findings at the International Salinity
Forum in Adelaide earlier this month.
He said that after 2000 the trend appeared to depend on depth to
watertable with more downward trends in areas of shallow
watertable.
“Persistent drought and high evaporative demand in the northern
agricultural region have offset groundwater rises since 2000.
But in much of the central region, the south-west and western
south coast, similar falls have not been measured despite lower
than average rainfall,” Dr George said.
Bores in the Department’s observation network are on cleared
agricultural land remote from the effects of any salinity
management treatment such as drains, trees or perennial
pastures.
Dr George said that in catchments that were still actively
filling with groundwater and had not yet come to equilibrium,
reduced rainfall appeared to have no discernible impact on
rising trends.
“As these catchments approach equilibrium and discharge areas
grow, we expect climate impacts to become the dominant
controller of trends.”
Dr George said that the recent change in groundwater trends may
have significant implications in assessing the likely future
extent of salinity and effect of management.
He cautioned that observed reductions in watertables must be
corrected for climate.
“Failure to do this may exaggerate the expected benefits of
management on the salinity problem.
“The data also has policy implications for the management of
farmland and public assets at risk of salinity,” Dr George said. |
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