CEO, Institute of Public Works Engineering Australia
Member, APWA International Affairs Committee
Editor's Note: This article is presented as part of the partnering agreement in place between APWA and its Australian counterpart, the Institute of Public Works Engineering Australia (IPWEA). The APWA International Affairs Committee proposes these articles to assist in the exchange of ideas between our international partners.
Salt is an inherent part of the Australian landscape.
Many areas in this country have naturally high levels of soluble salt in the soil and groundwater. Although salt is a natural, historical aspect of our soils and water, it has long been recognised that our human and land use practices, particularly our agricultural development practices, have changed our landscapes and natural systems.
These practices have significantly altered the natural balance of the water cycle. What was a slowly evolving historical process, has been accelerated to such an extent over the past 200 years that we now face a national problem of enormous significance and considerable economic cost.
The salts originate from either the weathering of salt bearing rocks, or are deposited on the land by wind, or rain transfer from the ocean. These salts are cycled throughout a catchment on a continuous basis, accumulating in the lower parts of the landscape.
In Australia, particularly in parts of the Murray Darling Basin, much of the salt that is now expressing itself at the surface, was deposited by seas which covered much of our existing landscapes. Millions of years of salt accumulation in sedimentary rocks and the slow release of salts found in crystalline rocks has led to the development of substantial concentrations of salts at or near the earth's surface.
Human activity (specifically agricultural development) post European settlement has disturbed these natural ecosystems and altered the existing hydrology. These landscape changes, which were dominated by annual pastures and crops, increased the amount of water that entered the landscape as deep drainage. This process has greatly accelerated the mobility of salts, flushing them through the landscape and into rivers, lakes, wetlands and groundwater.
In general, water is no longer used in the same way within the landscape, nor at the same rate. This has resulted in an accelerated pattern of leakage and in some areas caused groundwater to rise significantly.
Where irrigation of crops and pastures has been employed (particularly the "cost effective" flood irrigation of the past), percolation rates into the groundwater system are much higher.
The end result has been rising water tables that have mobilised stored salts and brought them to or near the soil surface.
Salinity has now risen to a level that is having adverse impacts on agricultural production, water supplies, aquatic ecosystems, biodiversity and, increasingly, on rural and urban infrastructure. These effects are being felt in every state of the nation.
National problem, local solutions
The City of Wagga Wagga, in southern New South Wales, has estimated that the repair and replacement costs for the assets damaged by salinity in their city are in the order of A$100 million ("A" refers to the Australian dollar). Wagga is implementing an Urban Salinity Action Plan and has invested A$4.5m to tackle the problem.
Problems caused by urban salinity are evident in parts of Western Sydney with estimates of 100,000 homes under threat. The local Regional Organisation of Councils (WSROC) has funding to develop a Code of Practice for urban development in Western Sydney to minimise the impacts of salinity on urban development.
Salinity is coming to a town near you...or at least in Australia it seems! More than 400 urban and rural local government areas are affected by dryland salinity across Australia.
The problems of salinity are widespread and have built up over many decades. It will require a sustained effort and significant resources over many years to redress the damage.
The Australian Government has committed A$700m over seven years as part of a national strategy to address salinity and water quality problems.
National Salinity Summit
Whilst salinity is a national issue, like many issues, its impacts will most be felt at a local community level. Many of the solutions will have to be found and implemented by local government-and public works engineers and other professionals will need to be at the forefront.
The IPWEA therefore recently joined forces with the Murray Darling Association, Sinclair Knight Merz Consulting, and the Australian Local Government Association to host the National Local Government Salinity Summit.
The focus of the Summit was to identify practical solutions that will mitigate the impact of salinity on roads, buildings, services, water quality, land use, and ultimately Local Governments' funding capacity.
It was noted that the greatest long-term impacts of salinity might not be on agriculture, but on the shortened lifespan of infrastructure assets such as roads, bridges, parks, underground services and buildings. An example is the damage to roads caused by rising saline groundwater. This can reduce sealed road life expectancy by up to 75 percent!
Salinity Handbook-Free Download
In recognition of these impacts on infrastructure, IPWEA commissioned a Salinity Management Handbook as a resource guide for engineers, public works professionals and others working in local government. This work was supported financially by the Australian Government's National Dryland Salinity Program.
National IPWEA President, Peter Taylor, launched the Local Government Salinity Management Handbook at the Summit. The Handbook provides an introduction to the current salinity situation in Australia from a local government perspective. It explains the causes of salinity and suggests mitigating measures that can be employed. It proposes a proactive role for public works professionals in tackling the salinity issue. Important first steps could include undertaking an audit of existing and potential impacts of salinity in local areas, and the commencement of programs to monitor whether water tables are rising.
Early feedback is that the Handbook is a most useful and valuable document. It can be freely downloaded from the IPWEA website by following the "Documents for Comment" link at www.ipwea.org.au/members/documents.
The 66-page IPWEA Salinity Management Handbook is seen as an evolving document. Comments are invited from practitioners in the field as to whether it meets their needs-or from those with experience in tackling this problem that can contribute to innovative solutions. Contributions from APWA members are most welcome on any of your own experiences...a worthy illustration of the value of international exchange of ideas!
For more information, please contact Chris Champion, IPWEA National CEO, by e-mail at email@example.com.