Water and Land Salinity Please check the updated statistics in the eResources Book
|Figure 4 Rising watertables in the |
Berriquin-Denimein Irrigation District
(source: Anon. 1990)
Prior to irrigation, watertables in the Shepparton Region of Northern Victoria were some 25 metres below the surface; now they are typically within 2 metres. Their rapid rise through the 1980s has been described as 'The Underground Flood': Figure 5 shows the situations in 1982 and 1990 (DARA 1989). To tackle the problem, the Shepparton Land and Water Salinity Management Plan has been put into operation. This is an integrated plan to achieve salinity control by reducing the quantities of water entering the groundwater and removing water from the watertable. It involves surface drainage, sub-surface drainage (including groundwater pumping), whole farm planning, and an environmental program (Anon. 1989). Similar problems are being tackled in nearby areas, such as to the west of the Campaspe River, and the Tragowel Plains to the east of the Loddon River.
A range of measures are being undertaken to combat rising watertables and salinisation in irrigation areas. These include surface and sub-surface drains (such as the Wakool-Tullakool sub-surface drainage scheme), groundwater pumping (as is being done to protect the main horticultural areas between Mooroopna and Tatura and south of Cobram in northern Victoria), using groundwater water for irrigation or disposal to evaporation basin, water harvesting (especially of drainage water), in some cases disposal of saline drainage water to the Murray (under the terms of the Salinity and Drainage Strategy), tree planting, and whole farm planning and management, especially in terms of water use management) and coping with saline environments ('living with salt'). Initially in experimental situations, saline drainage water is being used to irrigate treelots, at Loxton, and high value crops at Griffith (The Land, December 18, 1997).
Figure 5 Rising watertables in the Shepparton region. 1982 and 1990 (source: DARA 1989)
It is expected that all irrigation regions within the southern Basin will have water tables within 2 metres of the surface by about the year 2010 (Keyworth 1996). This will obviously affect the sustainability of agricultural production, particularly where the groundwaters are saline.
In spite of some early warnings (Wood 1924), secondary or induced salinisation was long thought to be only a problem in irrigated areas. No longer is this the case. Far greater areas have experienced changes to their vegetation cover and natural water balance in the interests of dryland agriculture. Over much of the Basin, as well as in other parts of Australia, arable and pasture lands are being affected by rising watertables and consequent dryland salinisation (Table 1).
Serious concern about dryland salinity is relatively recent, dating from the early 1970s in Victoria. Now it is recognised as a far bigger problem than irrigation-induced soil salinisation, certainly in terms of the area of land affected and perhaps also in terms of the value of agricultural production. There is no doubt that it is a major threat to agriculture in many parts of the Murray-Darling Basin (MDBC 1993). Data are still incomplete, but as more become available, the area continues to increase. For example,
In the SA mallee, where greatly increased recharge is resulting from clearing begun over 100 years ago, studies indicate that serious soil salinity may develop in the next 30 years. Indeed, low-lying areas east of Murray Bridge have already begun to be affected.
Recent groundwater modelling in the same region also shows that land management practices within a 40 kilometre-wide strip south and east of the River Murray will strongly influence river salinity for the next few centuries (Anon. 1991).
A 1993 Basin-wide study "conservatively estimated that at least 200,000 ha of land in the basin are now grossly affected and more than 1 million ha are at risk from dryland salinity" (MDBC 1993, vii). A more recent study has confirmed the general accuracy of figures for the Victorian part of the Basin (Allan 1994). Preliminary results from a new study into the possible future extent of dryland salinity in NSW indicate that if present land management practices continue, up to 5 million ha could be at risk in that State alone, with the Macquarie (east of Dubbo) (Hulme et al. nd), Lachlan, and Murrumbidgee (east of Wagga Wagga) river basins being the most susceptible (Bradd & Gates 1995). The true picture is not known, though the area is at least close to 600,000 hectares (Powell 1996). It is almost certainly greater than shown in Figure 6, which has been compiled from a number of sources to give as comprehensive a picture as possible of the problem for the Basin as a whole. Although much of the land affected by dryland salinity is within the MDB, the problem is also a national one, being particularly serious in the south-west of Western Australia (Table 2).
Figure 6 The extent of land affected by dryland salinity and urban communities with reported dryland salinity problems in the MDB (source: MDBC)
The current and potential consequences are very serious, not least in terms of land actually lost to agricultural production and the reduced productivity of land that is still being used. The fact that the area of land affected is likely to expand by 300 to 500 per cent over the next few years and that river salinity levels are rising over in much of the Basin, only adds to the concerns.
The following illustrations are two of the five focus catchments being studied as part of the National Dryland Salinity Research, Development and Education Program (Webb 1994).
The Loddon-Campaspe Catchment in northern Victoria covers 1.4 million hectares. In the upper parts of the catchment, native pastures are used for livestock grazing, while on the riverine plains to the north, dryland and irrigated cropping and pastures predominate. Dryland salinity is a major problem in the catchment, quite apart from that induced by irrigation in the irrigation areas. Currently, 11,000 hectares are visibly salt affected, with a further 61,000 hectares presently at high risk and an additional 93,000 hectares at further risk. The mean salinity level of the catchments' waterways is 4,300 EC, while the watertables are rising at 10 to 30 cm a year. An estimated 136,000 tonnes of salt leaves the catchments each year (Anon. 1995).
In tackling the problems, the community is playing the major role, not only through the development of salinity management plans, but also in carrying them out and paying for the work involved to be done. The main measures being undertaken are as follows:
- growing trees and perennial pastures, and improving crop management practices so rainfall is used where it falls;
- improving flood runoff management; and
- reducing leakages from irrigation channels and other infrastructure (Webb 1994, 15).
Such measures are being complemented by considerable monitoring and research.
The Liverpool Plains are located on the north-western slopes of NSW, north-west of Gunnedah. Covering just over one million hectares, the area is drained by the Mooki River and Coxs Creek, tributaries of the Namoi River. The highly fertile black earth soils, combined with the fact that nearly half of the area has a slope of under two per cent, make it one of the most inherently fertile areas in Australia (Schroder et al. 1991). Largely as a consequence of this, less than 15 per cent of the original vegetation remains. Cropping dates from the 1960s and it peaked in the late 1970s-early 1980s, but grazing has always been important. Whilst dryland salinity has long been present, its extent and severity have increased markedly since the late 1980s. An estimated 30,000 hectares have watertables within 2 metres of the surface; a further 195,000 hectares are at risk, with the watertables within 5 metres of the surface. In total, some 16 per cent of the catchment is at risk, and it is the most productive land (McDonald 1995).
As in the Loddon Campaspe catchment, the community is the driving force for remedial action, with support from New South Wales Government's Salt Action and the MDBC's Natural Resources Management Strategy programs. The main focus of the action being taken is to reduce accessions of water to the watertables. These must be reduced by at least 10-30 cm per year to prevent salinity increasing (Webb 1994, 17). Among other things, this will involve changing the traditional practice of growing wheat-soybean-wheat with long fallow periods, and making use of rotations, with lucerne and other perennial pastures, and opportunity cropping (using soil moisture when it is available) rather than long fallows (Webb 1994, 18).
Rising watertables and saline groundwater are not only affecting rural areas. Studies in progress indicate that off-farm dryland salinity is an increasing problem over large areas of the Basin (Watson et al. 1995). It is now recognised as an enormous problem in many urban areas (Figure 6), resulting in damage to roads and buildings, the corrosion of gas, water and sewer pipes, and the killing of trees, grass and other vegetation (Hamilton 1995). The problems are largely due to over-watering of gardens and public areas, roof run-off, and run-off from "waterproofed" areas. For example, some 60 per cent of the urban area of Wagga Wagga is at risk from highly saline watertables, rising by half a metre a year. Houses, public buildings, underground pipelines, public recreation areas, bridges, culverts and roads are all being affected. For example, the playing fields on the campus of Charles Sturt University and other places have been badly affected; even salt tolerant grasses are not surviving.
The costs of water and land salinity
In general terms, it has long been recognised that high water and land salinity levels impose significant costs on all users, agricultural, industrial and domestic.
The salinity levels are such as to cause significant problems for development uses, particularly agriculture and irrigated horticulture. High salinity levels reduce irrigation crop yields and can cause loss of orchard trees. In urban areas, salinity reduces the life of domestic and industrial equipment, increases maintenance costs for appliances and requires greater use of cleaning products (MDBMC 1987, 90).
Recently, however, studies have begun to quantify these costs in monetary terms. Overall, the estimated annual costs are substantial: $130 million in agricultural costs (see Agriculture), $100 million in infrastructure costs, and $40 in environmental costs.
The costs to agriculture have to be considered in various ways, not just in terms of lost production, but also reduced land values, detrimental aesthetic impacts, and costs of remedial action where these are feasible. In the Loddon Campaspe catchment, it is estimated that dryland salinity is costing farmers some $4.9 million per annum. On the Liverpool Plains, the costs are put at $11.3 million per annum, and are predicted to rise to nearly $72 million in ten years, through lost farm production, capital costs, and reduced economic activity. In the Shepparton region, salinity and waterlogging are currently resulting in productivity losses of at least 7 per cent. If nothing is done, losses of the order of 30 per cent will prevail within 30 years. It is estimated that this would result in the loss of 3,500 jobs by the year 2025 and massive economic and social dislocation in the region (Anon. 1989).
Off farm, the problems and costs may well be the larger and more serious than those on-farm. Preliminary studies indicate that rising watertables and dryland salinity are costing local governments at least $7.9 million a year in the Murray-Darling Basin, with well over half of the total being borne by councils in the Victorian part of the Basin (Table 3) (Oliver et al. 1996). For Wagga Wagga City Council, the cost of dryland salinisation is at least $800,000 a year and growing (Christiansen 1995). Rebuilding half a kilometre of the Sturt Highway on the western approaches to the city because of salinity damage cost $500,000. Many other towns and communities are similarly affected. For the rural shires, the major problem is the damage being done to roads and bridges. For example, in 1990, the Young Shire Council estimated the cost of road damage due to high watertables at $800,000. Boorowa Shire has returned over 30 kilometres of paved road to gravel because of high saline watertables and the consequent maintenance problems. The town of Yass is looking at the refurbishment of its water supply system, the cost of which may run into millions of dollars. In many areas, the main beneficiaries of measures to address dryland salinity are frequently off-farm (Carlos 1991). Such situations often justify targeted investment by governments in the interests of the wider community.
There are major problems for water users. River salinity is regarded as "a serious threat in many parts of NSW. Most salts, once dissolved in water, are not removed by natural processes and with present technology their removal is financially prohibitive, with costs around $100 per megalitre" (NSW 1994, 34). Many consumers are having to find alternative sources, such as bottled water. In the six years to 1994, it is estimated that increased salinity, as a consequence of further development within the Basin, has added an additional $1.5 million per year to the costs of water users (MDBMC 1995, 32). There are indications that some vegetable processors have not located in northern Victoria because of the prevailing salinity levels of the water.
On top of all of the above, are the non-market costs of salinity, such as the visual effects, the damage done to aquatic environments, and in some instances, the total loss of wetlands. Damage to some wetland areas affects the breeding of the Ibis, which plays a major role in controlling insects (see Wetlands and Forestry).
Tackling the salinity problems
In all parts of the Basin, governments and community groups are devoting large resources to tackling the water and land salinity problems, for example, the Salt Action programs in Victoria and New South Wales and the Community Action for the Rural Environment (CARE) program in South Australia.
A recent report has indicated that in the Murrumbidgee Irrigation Area, accessions to groundwater will have to be cut by more than 25 per cent - some 25,000 megalitres - to prevent more land going out of use. This will involve stricter controls on rice production, more efficient irrigation of all crops, more efficient water use by urban residents, and significant tree planting.
Whilst much can and must be done at the local level through the combined endeavours of communities and governments, the salinity problem is a Basin-wide one and must therefore be addressed at that level. It was the growing awareness of the salinity problems in the southern parts of the Basin that played a major role in the establishment of the Murray-Darling Basin Agreement and its first accomplishment, the 1988 Salinity and Drainage Strategy (SDS) (MDBMC 1988).
However, it is evident that the much larger problem of dryland salinisation is having an increasing impact on stream salinity, especially when flows are low. At the time of the preparation of the SDS, it was estimated that dryland areas would add up to 40 EC units at Morgan over the period 1986-2006. Such a figure now appears to be a significant underestimate. For example, as mentioned earlier, studies in a limited area of the Victorian riverine plain indicated that groundwater recharge resulting from clearing native vegetation for agricultural use could increase the salinity of the River Murray at Morgan by 140 EC within 50 years (Allison & Schonfeldt 1989). A key factor is that groundwater levels are rising throughout the Murray Basin, with no indication that this will be reversed in the foreseeable future. At the same time, many of the aquifers causing dryland salinity are shallow local systems which can be dealt with by local action.
The Natural Resources Management Strategy (NRMS) will therefore have a role in achieving the objectives of the SDS. At the same time, changes will be required in the Salinity and Drainage Strategy itself.
Both at government and community levels, considerable remedial and research work is being undertaken through the NRMS of the Murray-Darling Basin Ministerial Council. Some of the work is basin-wide, but there are also many regional and local projects, such as studies of soil salinisation and groundwater in the Macquarie Valley, various projects dealing with salinity management in the northern Victorian irrigation areas, dryland salinity abatement in the Forbes area, Campaspe dryland salinity management plan, and a salinity management plan for the Murray from Nyah to the South Australian border.
Much expensive revegetation work needs to be done on individual farms within a whole catchment approach. To assist farmers with the tree planting ad other work that forms part of catchment management plans, the MDBC is examining ways by which cost-sharing arrangements can be made for such work (MDBC 1996). Comparable attention needs to be given to the establishment of perennial shrubs and deep-rooted native pastures, which can play at least as important a role as trees**** (Figure 7).
Figure7 Reducing recharge by changing to perennial shrubs (source: Anon. 1996)
**** Of relevance here are the questions being raised about the true extent of the tree cover at the time of initial European exploration and settlement: see for example Ryan et al. 1995.
Continuing research is indicating an increasingly serious salinity problem throughout the Murray-Darling Basin. Average salinity in the Murray (as measured at Morgan) is rising at 1.5 to 5.0 EC units per year. The SDS was designed to achieve a 60-70 EC reduction at Morgan, but this will be more than wiped out by the latest findings (Williamson et al. 1995). An increase in River Murray salinity to around 900 EC would make the water unfit for human consumption significantly more often than it is now. If salinity increases that much, the proposals that a pipeline be constructed to take saline water to the sea (including one proposal for a polyethylene pipe laid on the bed of the Murray from Echuca to the River's mouth) could well be more attractive and viable (GHD et al. 1990).
Salt is a major feature of the Basin and its landscapes and will clearly become more so in the future. As has been indicated, this is in large measure due to a number of factors. The first is the excess recharge to groundwater and the consequent rise in the watertables, throughout the Murray Basin and in much of the rest of the MDB. The second factor is the substantial redistribution of salt that is occurring through the diversion of water, and hence salt, for irrigation (Lovering et al. 1998; see Groundwater Resources). The consequent reduced river flows also provide much of the explanation for increases in river salinity throughout the Basin.
The implications of the current salinity situation for the Murray-Darling Basin are extremely serious, even without any further growth in its scale and severity. Without the measures that have been taken, the situation would be far worse. However, they have yet to get to grips with the underlying causes. Clearly, it is a matter for all involved in land and water management. New and better ways of managing groundwater will have to be found. More water will have to be found for dilution flows and this can only come from water currently allocated to other uses.
Allan, M.J. (1994): An Assessment of Secondary Dryland Salinity in Victoria. Technical Report No.14. Centre for Land Protection Research, Department of Conservation and Natural Resources, Bendigo.
Allison, G.B. & Schonfeldt, C.B. (1989): "Sustainability of water resources of the Murray-Darling Basin". 12th Invitation Symposium: Murray-Darling Basin - a resource to be managed. Preprint No. 8: 149-161. Australian Academy of Technological Sciences and Engineering, Melbourne.
Anon. (1989): Shepparton Land and Water Salinity Management Plan: draft. Goulburn-Broken Region Salinity Pilot Program Advisory Council, Shepparton.
Anon. (1990): Watertables within the Berriquin Irrigation District. NSW Department of Water Resources, Deniliquin.
Anon. (1991): Measuring Dryland Recharge for Better Land Use Planning. Seeking Solutions No. 9. Division of Water Resources, CSIRO, Canberra.
Anon. (1995): "Profile on the Loddon Campaspe focus catchment". Focus: a newsletter of the National Dryland Salinity Research, Development and Extension Program, 4, 2-9.
Anon. (1996): "Innovative ways to manage recharge in the Mallee". Focus (Newsletter of the National Dryland Salinity Research, Development and Extension Program), Issue 6, 6.
Bradd, J. & Gates, G. (1995): "The progression from site investigation to GIS analysis to map dryland salinity hazards in NSW". pp. 50-55 in Murray-Darling 95 Workshop: extended abstracts Wagga Wagga 11-13 September 1995. Record No. 1995/61. Australian Geological Survey Organisation, Canberra.
Campbell, A. (1998): "The extent, future trends, research and development of dryland salinity". pp. 1-5 in Marcar, N. (Editor) Managing Saltland into the 21st Century: conference papers. National Program on Productive Use and Rehabilitation of Saline Land, Canberra.
Carlos, C. (1991): "What is town water worth?" Australian Journal of Soil and Water Conservation, 4(3), 32-36.
Christiansen, G. (1995): The Economic Costs of Urban Salinity: the Wagga Wagga experience. NSW Department of Land and Water Conservation, Wagga Wagga.
DARA (1989): Salinity: the underground flood. Can it be controlled in the Shepparton Irrigation District? Victoria Department of Agriculture and Rural Affairs, Shepparton.
GHD et al. (1990): A pipeline to the Sea: pre-feasibility study. Gutteridge Haskins & Davey and others for the Murray-Darling Basin Commission, Canberra.
Gibson, G. (1997): Dryland Salinity: an informal discussion guide. Murray-Darling Basin Commission, Canberra.
GWG (1996): Murray-Darling Basin Status of Groundwater 1992. Groundwater Working Group Technical Report No. 2. Murray-Darling Basin Commission, Canberra.
Hamilton, S. (1995): "Urban salinity in the Murray-Darling Basin". pp. 120-123 in Murray-Darling 95 Workshop: extended abstracts Wagga Wagga 11-13 September 1995. Record No. 1995/61. Australian Geological Survey Organisation, Canberra.
Hulme, P. et al. (nd): Salinity in the Lower Macquarie Valley. Macquarie Valley Landcare Group, Warren.
Keyworth, S.W. (1996): "Sustainable irrigation in the Murray-Darling Basin". Focus (Australian Academy of Technological Sciences and Engineering), No. 90, 5-9.
Lovering, J.F. et al. (1998): "Salinity in the Murray-Darling Basin: a critical challenge for the 21st Century". pp. 215-230 in Weaver, T.R. & Lawrence, C.R. (Editors) Proceedings of the IAH International Groundwater Conference. Groundwater: sustainable solutions. International Association of Hydrogeologists, Brisbane.
McDonald, J. (1995): "Dryland salinity in the Liverpool Plains". pp. 221-229 in Outlook 95: commodity markets and natural resources. Australian Bureau of Agricultural and Resource Economics, Canberra.
Meacham, I. (1984): The River Murray Salinity Problem: a discussion paper. River Murray Commission, Canberra.
MDBC (1993): Dryland Salinity Management in the Murray-Darling Basin. Murray-Darling Basin Commission, Canberra.
MDBC (1996): Cost Sharing for On-Ground Works. Murray-Darling Basin Commission, Canberra.
MDBMC (1987): Murray-Darling Basin Environmental Resources Study. Murray-Darling Basin Ministerial Council, Canberra.
MDBMC (1988): Salinity and Drainage Strategy. Murray-Darling Basin Ministerial Council, Canberra.
MDBMC (1995): An Audit of Water Use in the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra.
NHMRC (1996): Australian Drinking Water Guidelines: summary, 1996. National Health and Medical Research Council / Agricultural and Resource Management Council of Australia and New Zealand, Canberra.
NSW (1994): Our Water: a review of the current status of the water resources of New South Wales and the key issues relevant to their future development. Second edition. New South Wales Government, Sydney.
Oliver, M. et al. (1996): Costs of Salinity to Government Agencies and Public Utilities in the Murray-Darling Basin. ABARE Research Report 96.2. Australian Bureau of Agricultural and Resource Economics, Canberra.
Powell, J. (1996): "Managing dryland salinity in the Murray-Darling Basin". Focus (Australian Academy of Technological Sciences and Engineering), No. 91, 2-6.
Ryan, D.G. et al. (1995): The Australian Landscape: observations of explorers and early settlers. Murrumbidgee Catchhment Management Committee, Wagga Wagga.
Schroder, D. et al. (1991): Dryland Salinity: Liverpool Plains. Department of Conservation and Land Management, Sydney.
Webb, A. (1994): Planning for a National Salinity Program: assessment of five focus catchments. Occasional Paper Series No. 05/94. Land and Water Resources Research and Development Corporation, Canberra.
Williamson, D.R. et al. (1995): "Trend in salt concentration and salt load of stream flow in the Murray and Darling Drainage Basins - the historic picture". pp. 262-265 in Murray-Darling 95 Workshop: extended abstracts Wagga Wagga 11-13 September 1995. Record No. 1995/61. Australian Geological Survey Organisation, Canberra.
Williamson, D.R. et al. (1997): Salt Trends: historic trend in salt concentration and saltload of stream flow in the Murray-Darling Drainage Division. Dryland Technical Report No. 1. Murray-Darling Basin Commission, Canberra.
Wood, W.E. (1924): "Increase of salt in soil and streams following the destruction of the native vegetation". Journal of the Royal Society of Western Australia, 10(7), 35-47.
|Slightly affected||Land exhibiting a reduction in salt sensitive plant vigour, some salt-tolerant plants, seasonally or permanently shallow watertable, scalds (if present) are small|
|Moderately affected||Land exhibiting a significant loss of salt-sensitive plants, salt-tolerant plants are common, seasonally or permanently shallow watertable, scalds up to about 5 square metres in size, some erosion present.|
|Severely affected||Land exhibiting an absence of salt-sensitive plants, permanently shallow watertable, large scalds, often badly eroded|
Source: MDBC 1993, 15.
|State||Area affected, in hectares||Area at risk, in hectares|
|New South Wales|
* Much of the area in Western Australia was marginally saline before clearing.
Sources: Gibson 1997; Campbell 1998.
|Roads and bridges|
|Footpaths, bicycle paths|
|Water pipes and supply systems|
|Sewerage pipes and disposal systems|
|Public fencing, stockyards|
|Municipal parks, gardens and playing fields|
|Other (garbage land fills, waste disposal sites and drainage works)|
Source: Oliver et al. 1996, 40.