Soil salinity and dryland salinity are two problems degrading the environment of Australia. Salinity is a concern in most states, but especially in the south-west of Western Australia.Monitoring the white death – soil salinity . Australian Academy of Science.
The Eastern Mallee and the Western Mallee of Western Australia are some areas that are prone to salinity with little remedial action being undertaken to rectify the problem. Lands surrounding Lake Bryde-East Lake Bryde and Dumbleyung Lake have also been affected.
In the Murray River valley, irrigation has caused salinity problems. Land surrounding the town of Werrimull in the northwest of Victoria have been affected by salinity due to land clearing.
Process The soil in Australia naturally contains salt, having accumulated over thousands of years. This salt may come from prevailing winds carrying ocean salt, the evaporation of inland seas, and from weathered parent rocks. Rainfall absorbs this salt on the surface, and carries it down into the subsoil where it is stored in unsaturated soil profiles, until it is once again mobilised by ground water and rising water tables.Bell, David (1999). Australian Trees for the Rehabilitation of Waterlogged and Salinity Damaged Landscapes. Australian Journal of Botany, 47: 697–716. When this ground water comes closer to the surface, this salt is also brought up. As the water eventually evaporates, it leaves behind all this concentrated salt, resulting in soil salinity. This can be caused by an imbalance in the hydrological cycle, or by irrigation.
Prior to British settlement in 1788, groundwater levels were in equilibrium. Seasonal recharge, and year-round utilisation of ground water by deep rooted native vegetation resulted in ground water levels remaining static.C.J. Clarke, R.J. George, R.W. Bell, T.J. Hatton (January 2002). Dryland salinity in south-western Australia: its origins, remedies, and future research directions, Australian Journal of Soil Research, 40(1): 93–113. Land clearing in Australia has resulted in a loss of this native vegetation, replaced largely by agriculture and pasture crops. These are often shallow rooted annual plants which are unable to intercept and adequately absorb stored and rising ground water. This creates an imbalance in the hydrological cycle, and results in dryland salinity. Salinity is classified as a dissolved salt content of a substance like soil or water. Salinity can prevent crops and other vegetation from growing leaving land empty.
Irrigation is also a contributor to salinity. Firstly, the addition of irrigation acts to simulate rainfall, and if not applied at appropriate levels, can result in the recharge of water tables, and promotes rises in the water table.Pels, S. 1978. Waterlogging and Salinization in Irrigated Semi-arid Regions of NSW. Search Volume 9, pp 273-276. Secondly, irrigation water itself can contain salts, which are deposited into the soil with its use. This level of salt can range from 0.5 - 2 tonne per hectare per year, and can greatly increase natural salt levels.
Effects and impacts Over time this process has caused the thin top-soil layers to become irreversibly salty and no longer suited for agriculture. By 1999 an estimated 2.5 million hectares of land had become salinised since the introduction of European farming methods.
Currently, around 5.7 million hectares of land is classed as having 'high potential' for salinisation with that number expected to rise to 17 million hectares by 2050.Salinity. Department of Sustainability, Environment, Water, Population and Communities.
High soil salt levels have dramatic impact on plant root zones, in both native vegetation as well as agricultural and pasture crops, natural wetlands and surrounding water ways. An increase in salt can decrease the ability of plants to absorb water through their roots by osmosis, cause leaf burn and necrosis through increased levels of sodium and chloride, and create nutrient and ionic imbalances resulting in poor growth and death. Department of Primary Industry, NSW government Salinity can also adversely affect infrastructure such as roads, buildings, underground pipes and cables through oxidation.
Muehlenbeckia horrida subsp. abdita, commonly known as the Remote Thorny Lignum, is a critically endangered species due to its intolerance to salinity.
Impacts by state New South Wales Currently 5% of New South Wales is affected by dry land salinity, and around 50% is under threat. 15% of current irrigated land is impacted, and up to 30% is currently under threat. The main regions currently affected, and at high risk, are The Murrumbidgee River catchment near Griffith, and Jemalong River Catchment near Forbes, as well as the Murray River irrigation area near Deniliquin.
Victoria The current levels of salinity in Victoria are relatively small, with the main impact expected to occur in high risk areas in the coming years. These high risk areas include the Campaspe, Loddon, Corangamite, Glenelg-Hopkins, Goulburn-Broken catchments, and Wimmera and Mallee regions. The current cost to Victoria is estimated at $50million per year. This is expected to rise significantly with the impacts on agricultural land, wetlands and infrastructure in high risk areas to increase, mainly in part to an anticipated 10 fold increase in salt levels by 2050.
Western Australia Western Australia contains the majority of land affected by salinity in Australia, with around 70%. Over 2 million hectares are currently affected, and around 4 million hectares of land are currently listed as high risk, and 50% of divertible water is already considered overly saline. Around 450 plant species are endemic to areas that are at high risk of salinisationGeorge R, Short R, Short B & Pinjarra, 2006. Estimating the extent of salinity. Western Australian Department of Agriculture and Food.
South Australia Salinity in South Australia is a problem in all principal agricultural areas, with 370000 hectares of land and wetlands impacted. At current rates, this is expected to increase by 60% by 2050. Australian Natural Resources Atlas, Department of Sustainability, Environment, Water, Population and Communities. It is expected to cost the state around $47million per year in lost agricultural profit, and is expected to taint more than 20% of ground water to levels above those safe for human consumption.
Tasmania Tasmania is relatively unaffected by salinity, with around 1% of agricultural land, and 8% of farm land adversely affected by salt, resulting in a current cost to the state of around $5million per year, rising to around $13million by 2050. The majority of this salinity is irrigation based.
Queensland Queensland is the least affected state of Australia, due to its unique seasonal rainfall. Around 15000 hectares are currently affected, with 3.1million hectares considered highrisk. At current rates however, salinity is predicted to have moderate scale impacts on land and infrastructure by 2050, with 12,000 km of roads, 1500 km of rail lines, and around 2.8million hectares of agricultural land, remnant vegetation, and wetlands and streams negatively affectedBrough, M. 2007. Salinity. Department of Natural Resources and Water, Queensland State Government.
Impact reduction and management Government initiatives The Australian governments have taken an integrated approach to target different scales of management. The approach is to manage the salinity issue at national, regional and state levels, down to local and individual farmers. Since 1983 the Australian governments have actioned the National Soil Conservation Program, National Landcare Program, Natural Heritage Trust, National Action Plan for Salinity and Water and Caring for our Country.
The National Landcare Program focused on improving resource management and practices at the farm and local level.National Landcare Program Review 2003. Department of Agriculture, Fisheries and Forestry. The National Dryland Salinity Program (1993 to 2004), funded a broad range of research and development from which to roll out further government programs.Van Bueren, M., and Price, R.J., 2004, Breaking Ground — Key Findings from 10 Years of Australia’s National Dryland Salinity Program . Land & Water Australia, Canberra.
The National Action Plan for Salinity and Water Quality (NAPSWQ), implemented together with the Natural Heritage Trust (NHT) program, ran from 2000 to 2008. The NAPSWQ was adopted through an intergovernmental agreement between Australian commonwealth, state and territory governments. The plan aimed to help support community action and land managers in adversely affected catchments, and was rolled out by regional Natural Resource Management (NRM) organisations. The governments committed $1.4 billion over seven years to tackle the salinity problem. The plan involved input and participation from government, community, local business and land managers. The NAPSWQ focused on 21 regions across Australia that were deemed; through hazard assessments and dryland salinity risk, to be most affected by salinity and water problems.Australian Government 2008 What is the National Action Plan for Salinity and Water Quality? The goal of the NAPSWQ was to motivate and enable regional communities in preventing, stabilising and reversing trends in salinity; improve water quality and secure reliable allocations for both human, industrial and environment use.Sinclair Knight Merz 2006 Evaluation of salinity outcomes of regional investment . Report to the Department of the Environment and Heritage and Department of Agriculture, Fisheries and Forestry April 2006. The overarching objectives of the NHT were biodiversity conservation, sustainable use of natural resources, community capacity building and institutional change. The final report for the NAPSWQ states that ‘With few exceptions the massive efforts involved in delivering NAPSWQ and NHT programs have at best halted the degradation of these resources. This has reinforced the view of the State of Environment (SoE) Report that concluded that the condition of these resources continues to decline despite the best efforts of the community and government'.State Natural Resource Management Office 2010 National Action Plan for Salinity and Water Quality and Natural Heritage Trust program 2003–2009 Final Report. Prepared for Western Australian State Government March 2010 p.1
In 2008 the initiative Caring for our Country was started to replace the National Action Plan, which had ceased.National Action Plan for Salinity and Water Quality . Retrieved on 19 September 2011 This Australian Government initiative aims to build on the work done under the NAPSWQ,Australian Government 2011 Natural Resource Management - Monitoring, evaluation, reporting and improvement for Caring for our Country . focusing on a more targeted asset-based approach,Alexander, Jennifer; Roberts, Anna and Pannell, David J. 2010 Victoria catchment management approaches to salinity: learning from the National Action Plan experience. Australasian Journal of Environmental Management, 17(1): 45-52. and aims to build attitudes of environmental stewardship.
Case study examples Salinity management in the Murray-Darling Basin has included investment in salt interception schemes, rehabilitation of irrigation areas, and programs to educate landholders and irrigators on better practicesGovernment of South Australia 2009 Salinity and water quality - Government of South Australia. Retrieved from: http://www.sa.gov.au/subject/Water%2c+energy+and+environment/Water/River+Murray/Allocations+and+water+information/Salinity+and+water+quality