Drains can work but water may need treatment
Released 11 May 2009
Mr Ruprecht says ongoing investigations by Department of Water researchers under the Engineering Evaluation Initiative (EEI) have shown that such drains can be effective in countering salinity, but farmers need to be aware that such drains can have detrimental downstream impacts.
"One impact, if not the key downstream impact that needs to be addressed in planning for salinity engineering works - is acidic groundwater," Mr Ruprecht said.
"The research has shown that acidic waters can adversely affect aquatic plants and animals in creeks and other receiving environments."
Results of a partnership project between the Department of Water's EEI, the Cooperative Research Centre for Landscape Environments and Mineral Exploration, CSIRO and Department of Agriculture and Food show that acidity (that is, water with pH less than 5.5) is widespread in many shallow saline groundwaters in the eastern wheatbelt, along with dissolved metals such as iron and aluminium and sometimes trace metals such as lead, copper, zinc and nickel.
Mr Ruprecht said that the groundwater acidity was believed to be very old and rising watertables had brought this to the surface, along with salt.
"This rising saline water has also caused some lakes to become acidic, in addition to being salinised," he said.
"A key finding by CSIRO scientists has been that the acid in the waters can also be transformed and stored in new minerals forming in drains and lakes, and has parallels with the acid lakes forming on the Murray-Darling.
"But while acidic groundwater is an issue, there are options to manage their impacts, including the use of storage, retention and evaporation basins or treatment systems."
"Preliminary findings from trials conducted by the Department of Water with funding from the Avon Catchment Council indicate that it is possible to neutralise the acidity in drainage waters using either lime sand, hydrated lime or composting wetlands in a range of simple, easy to set-up treatment systems.
"People digging deep drains to counter salinity need to be aware that the salty water drained from their farm could end up causing environmental problems for their neighbour's property or a creek or waterway downstream.
"These impacts may happen over a longer timeframe without the use of deep drains, but they may be accelerated many times and brought forward in time by using drains to manage salinity.
"As a result, managing such downstream impacts is crucial to the successful planning and implementation of sustainable deep drainage systems.
"A simple rule of thumb is to plan such drains with the end receiving environment in mind. That is, always ensure that your drainage plan includes options for the safe disposal or management of any waters from your property."
The EEI findings are part of the Department of Water's ongoing investigations into the use of engineering methods to counter salinity in the Wheatbelt.
Mr Ruprecht said the report on acidic groundwater and a summary brochure was available on the department's website, and with the EEI drawing to a close would soon to be complimented with the report findings of other EEI projects.
The Engineering Evaluation Initiative (EEI) is a priority project under the National Action Plan for Salinity and Water Quality, jointly funded by the WA and Australian Governments.
The initiative carried out projects 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.
It also looked at the effect of any acid groundwater produced and the most effective methods of safely disposing of the saline waters that come out of such drains and pumping projects.
With the Engineering Evaluation Initiative drawing to a close, further findings of EEI investigations will be released in coming months. This is expected to include several regional seminars involving rural communities to consult with farmers on their options for improved water management.'
Contact: Dianne Dixon
Phone: (08) 6364 6983 / 0419 910 847