The use of large-scale and regional drainage systems to counter salinity in the Blackwood catchment will be the subject of public meetings in Wagin and Moodiarrup this week.

The meetings will consider the findings of the Blackwood Regional Drainage and Water Management Evaluation.

“This study assessed a range of options - including large-scale drainage systems - to improve the management of water resources in the catchment,” Department of Water manager salinity and water

resource recovery officer Tim Sparks said.

“The aim was to identify better ways for farmers, catchment managers and the community to manage dryland salinity, reclaim valuable agricultural land and to lower salinity in the Blackwood River.”

The Department of Water and CSIRO are conducting the information sessions, which will be co-hosted by the Blackwood Basin Group.

Ongoing research by the Department of Water has found deep drains can be effective in helping counter salinity on farms in the Wheatbelt.

Preliminary findings from the Department’s Engineering

Evaluation Initiative reveal that farmers need to be clear from the start about what they want to achieve with drainage.

Drains might not be effective in all cases; downstream impacts need to be considered; and ultimately, drains might be too costly an option.

The department’s director of water resource management John Ruprecht said departmental research indicated that drains planned and designed to suit local conditions and soil types can effectively lower water tables and allow protection or re-establishment of vegetation or crops.

Mr Ruprecht said the EEI study also found there could be problems with acid groundwater produced by drains in some areas, and that there are environmental risks associated with disposing of water from most drains.

The work forms part of the department’s ongoing investigations into the use of engineering methods to counter salinity in the Wheatbelt, and was a priority project under the National Action Plan for Salinity and Water Quality, jointly funded by the State and Federal Governments.

Thirteen projects have been carried out under the initiative to investigate the effectiveness of engineering solutions to combat salinity in the Wheatbelt.

The projects investigated methods such as deep drainage, groundwater pumping, and farm-scale evaporation basins to help farmers better manage salinity at Dumbleyung, Tammin, Bodallin, Pithara,

Morawa, and Beacon.

Research also evaluated the effect on receiving environments of acid and saline drain discharge, and the most effective methods of treating and managing the waters that come out of such drains and pumping projects.

“This has been a very thorough investigation into the effectiveness of drains to counter salinity,” Mr Ruprecht said.

“It included drains up to three metres deep and extending for 22 kilometres, with water from two of the drains collected in evaporation ponds.

“There’s no doubt digging deep drains to counter salinity can work.

“At our Dumbleyung study site monitoring showed that groundwater levels were lowered adjacent to the drain, and the water discharged by the drain was removing salt.

“The EEI has also demonstrated that when planned properly with a clear objective, drains can significantly lower the water table enough up to 250 metres away.”

Mr Ruprecht said digging drains is expensive and some farmers baulked against drainage as an option for managing salinity because of this high cost.

He said farmers needed to determine issues such as whether they wanted to lower the watertable across a catchment, or make specific saline sections of paddocks grow crops again, and where to dispose or manage the waters from a drain.

“Several thousand kilometres of deep and shallow drains have been constructed in the Wheatbelt in recent years but no-one has scientifically looked at how effective they are, what precautions should be taken, and the dangers involved in simply moving salty water from a salinity-affected farm further downstream or into a neighbour’s land,” Mr Ruprecht said.

“This sort of salinity research and development is important to ensure that property owners can decide how best to spend their money and time to fix salinity on their land, without creating potentially worse problems downstream.