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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
CASE STUDY: Merredin town site, Western Australia
Groundwater pumping and desalination project
Merredin is a regional centre in Western Australia's eastern wheat belt. Rising watertables and salinity have concerned the local community and authorities for at least 15 years. Through the State's Rural Towns Program, the Merredin town site has become the subject of detailed groundwater investigations. Recent test pumping results and computer groundwater modelling suggest that lowering the watertable by pumping would be an effective salinity control measure.
The rising saline watertable threatening the town site could be turned into a resource by desalination for drinking water. This could then be used to supplement the town water supplied from Mundaring Weir via the Kalgoorlie pipeline.
Results of groundwater investigation and modelling
Modelling has shown that to protect the whole town, nine bores each producing 50 kL/day would be required to keep groundwater levels at a safe depth.
Watertables now 2.5 to 3.0 m below ground would be lowered, effectively controlling groundwater levels and salinity under about 15 ha of the Merredin central business area. Two recently installed production bores are being used to draw 100 kL/day of moderately saline (30 000 µS/cm, or approximately half seawater quality) groundwater from under the town.
Merredin pilot project
A twelve-month joint pilot project involving Agriculture Western Australia, the Water Corporation and the Merredin Shire, and funded by the State Salinity Council's Community Support Scheme 2000 has begun.
Two hectares of evaporation ponds are to be located about 4 km west of the town centre and will dispose of the water produced by the two bores. A desalination plant adjacent to the evaporation ponds will produce potable water from 10% of the supply. This desalinated water will supplement the town supply via a Water Corporation reservoir. Discharge water from desalination will be returned to the evaporation basin.
Using some of the groundwater as it is pumped to the ponds reduces the volume for disposal by evaporation. This provides considerable economic advantages in both production of potable water and the reduction in size of the evaporation basin required.
The project is a double winner - pumping groundwater will alleviate the salinity risk, and will provide a source from which drinking quality water can be produced. Supplementing the town water supply will enable residents to reduce their dependency on water from the pipeline.
If successful, an expanded and longer-term scheme will be installed in Merredin. Similar schemes may then be employed in other salt-affected towns in Western Australia.
Table of Contents for the Australian Dryland Salinity Assessment 2000
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