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Yarra Yarra farmers tackle rising groundwater
One million hectares of farming land, one group of farmers and one large drainage rehabilitation project. That is the reality of the saline groundwater battle going on in the Yarra Yarra Catchment of Western Australia's Northern Agricultural Region.
Wheat and sheep farmers from the Yarra Yarra Catchment Management Group have tackled the problem of rising groundwater through careful studies over six years under a project coordinated by the Northern Agricultural Catchments Council.
Funding
The project is funded by the Australian Government. The State Government also provides cash and in-kind contributions.
Activities
The studies culminated in the excavation of a pilot drain 10 kilometres long and 2.1 metres deep allowing groundwater to flow into part of a natural evaporation area or chain of salt lakes - the focal point of the Yarra Yarra catchment basin.
Project Manager Max Hudson said during the study period an extensive drilling programme established over 600 observation bores along drainage lines to identify the extent of the shallow groundwater.
"A series of workshops held with farmers showed the main problem was rising saline groundwater locked beneath the valley floors," Max said. "A computerised Geographical Information System was used with aerial photography and precise topographical information. As a result, farmers discovered that despite 20 years of surface water control and extensive replanting of valley floors and mid slopes it had had a minimal impact.
"Farmers took this on board, even though replanting had taken a lot of time and money. Now we know with land that has been cleared for more than 50 years, there's not much chance of getting the water table down with plants, you also need to dig drains to release the groundwater, at the same time ensuring there's no detrimental ecological effect."
Overwhelming anecdotal evidence and some scientific investigations show deep drainage combined with previously established control methods can be a sustainable solution in some landscapes. Design criteria has been developed for a cost-effective, robust and sustainable construction to ensure groundwater in the drains is managed as a separate entity excluding all external surface water.
To gauge the effectiveness of the work, a soil scientist and botanist have been monitoring existing drains, with favorable outcomes. However more widespread investigation is needed in each of the 11 management zones to account for different soil types.
The Yarra Yarra is now looking at a series of on-ground investigations involving up to 300 kilometres of drains under intensive scrutiny through a monitoring programme.
More information
- Max Hudson, Project Manager: (08) 9667 1021 or hmhudson@bigpond.com
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