Managing salinity
Department of Water aims to manage and protect key water resources. Where salinity is a problem, the department recommends management practices that ensure salinity levels are kept low enough to permit sustainable use of water for today and for future generations. The protection or improvement of these key and potential water resource catchments also promotes a healthy landscape and environment. This issue is one of Western Australia's biggest environmental problems.
Salinity of streams or land is closely linked to groundwater interaction with surfacewater and often linked to clearing of native vegetation. Its causes are explained in more detail in Understanding Salinity.
Impact
In the south-west of the state, 18 million hectares of the 25 million originally covered by native vegetation have been cleared mostly for agricultural purposes. As a result, 1.8 million hectares are now salt-affected and either cannot grow crops previously grown there or have severely reduced yields. This affected area keeps expanding slowly and is not expected to reach equilibrium for several decades.
Salinity is affecting our natural environment, water resources, agriculture, and important infrastructure such as towns, roads and railways.
Mortlock East River culvert showing signs of salt degradation
Photograph by Peter Muirden
Yilgarn River culvert showing effects of land clearing, waterlogging and salt
Photograph by Peter Muirden
Tackling salinity
The department, and its former agencies, have been successful in delivering science and effective responses to the ongoing issue of salinity on land and in our water over many decades. Changes in land management can alter the salinity of the downstream receiving water bodies. It is important to keep protecting the current and future water resources that might deteriorate in terms of quantity and quality if not managed carefully.
Some forest management activities need to be managed for water quality risk to water resources. State forests are managed by the Department of Parks and Wildlife, though the Department of Water also owns forested land. The departments work together to manage these resources and in preparing and evaluating the Forest Management Plans and silvicultural guidelines.
Mining for bauxite occurs in the water supply catchments in the Darling Range of Western Australia and is controlled by state agreement Acts. The department sits on the Mining and Management Program Liaison Group (MMPLG) and both chairs and administers the Bauxite Hydrology Committee. This ensures the department can provide technical advice and recommendations on hydrology and stream zone ecology to protect the water resources from the effects of mining.
Recently the resources available to undertake the salinity management program in the department under the State Salinity Action Plan 1996 and subsequent {Salinity Strategy March 2000} have been reduced considerably; some of the work programs have been completed while other salinity work was replaced by higher priority state government initiatives.
The work has contributed significantly to the state's understanding of the impacts of land use change (clearing and mining) on water resources and contributed to stabilisation and in some cases recovery of important water resources.
The Salinity program review (2012) recognised catchments where the risk to public assets from salinity was high enough to justify retaining existing clearing controls and keep a 'watching brief' in water resource recovery catchments. Other components of the program have been documented and published as design principles and best environmental practices for Drainage in the Wheatbelt. External components, such as Natural Diversity Recovery Catchments that protect significant natural areas are managed by the Department of Parks and Wildlife.
The last decade has seen many achievements and improvements in understanding and managing the state's salinity problem and the impacts of mining and forest and vegetation management on water assets. These achievements include:
- Successful trial of saline diversion technique in East Collie River and development of a treatment approach for inland desalinisation
- Management of Wellington Plantings Estate for a 800 mg/L salinity benefit to Wellington Reservoir
- Recovery of Denmark River from impacts of salinity
- Implementation of the Engineering Evaluation Initiative and Wheatbelt Drainage Evaluation ($6.8 M initiative including construction of 10 drainage trials, 3 pump systems and 2 treatment systems of saline acidic water)
- Development of {Inland Drainage Policy Framework}
- Development and provision of high level science that guides water resource management in dryland areas and state forest. This science has been documented and is widely used by stakeholders.
A summary of the salinity status and trends is available in the Stream salinity status and trends report, 2005. Monitoring of flow and salinity in key water resources is vital to capture any changes in salinity status and trends early so as to intervene in catchment management.
A range of reports providing technical advice and support for managing and understanding the impacts of salinity are now available.
Country Areas Water Supply Act (1947) clearing controls
The Clearing Control Catchments are proclaimed under the Country Areas Water Supply Act 1947 to limit the clearing of indigenous vegetation in some existing or potential water supply catchments in the South West of Western Australia where the permanent clearing of indigenous vegetation would cause an increase in the salinity of water resources.
There are six South West river catchments where the clearing controls apply:
- Mundaring Weir Catchment Area
- Wellington Dam Catchment Area
- Harris River Dam Catchment Area
- Warren River Water Reserve
- Kent River Water Reserve
- Denmark River Catchment Area
- CAWSA boundaries spatial data
Flow and salinity monitoring has shown that the clearing controls have been very successful in arresting further salinisation of water resources in the controlled catchments.
The Environmental Protection Act clearing legislation, introduced in July 2004 has primacy over Country Areas Water Supply Act 1947 clearing controls. Consequently, land owners or occupiers considering clearing indigenous vegetation in the clearing control areas should first contact the Department of Environment Regulation for advice as to whether an EP Act Clearing Permit or a CAWS Act Licence to clear is required.
Reference material
Stream salinity status and trends in the south-west of Western Australia
Water yield response to land use change in south-west Western Australia
Preliminary assessment of rainfall and groundwater trends in areas of Wandoo
Groundwater information and management options for the Brockman River catchment
Groundwater information for management of the Upper Canning Southern Wungong catchment
Natural resource management in WA; Salinity strategy, March 2000