DRYLAND SALINITY
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Proceedings of the 10th
International Conference on Environmental Science and Technology
Kos island, Greece, 5 – 7 September 2007
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DRYLAND SALINITY
P. CRENNAN
EXTENDED ABSTRACT
The landform of much of the productive agricultural area in Australia has an underlying
watertable above which is a subsoil profile containing naturally occurring salt. Imported,
inappropriate farming practices have introduced excessive water into the landform causing
the watertable to rise thereby dissolving salt and concentrating it within the root zone of
plants (within 2 metres of the surface). Salty water is discharged into the rivers and streams
impacting on water quality throughout the river system.
Agricultural production is damaged along with the ecosystems of remnant native vegetation
and wetlands with consequences for the native fauna which is dependant upon those
features. Once mobilized the salt affected soil is irreversibly damaged. The land already
damaged and at risk coincides, in the State of New South Wales, with the productive farming
and grazing lands in the area known as the Murray-Darling Basin.
The entry of water to the watertable is known as “recharge” and the appearance of salinity is
known as “discharge”. In a local groundwater system the recharge and discharge areas may
be close-by however regional groundwater systems may extend over 100 kilometres. In a
system of private land ownership the downstream farm (or fragile ecosystem) in the
discharge area has no relationship with, or control over the farming practices in the recharge
area but will bear the impact and suffer the loss.
Salt concentration is measured in units of electro-conductivity (EC) both in the soils and as it
is discharged into the river system. Commonwealth and State Governments in Australia
have set targets based on the EC measurement of water in rivers at identified locations. The
co-operation of landholders with various agencies is sought to achieve the targets but the
existing sophisticated land use planning system already in place and implemented by the
third tier of government in Australia, Local Government, is largely being ignored at the peril of
the environment.
Keywords: Australia; dryland salinity; land use planning; watertable; salt; unconstrained
agricultural development; native vegetation; recharge areas; biodiversity; ecosystems.
INTRODUCTION
Whilst the issue of salinity in Australia has risen to prominence in the last five years, the
existence of the problem has been acknowledged for a number of decades. Awareness was
raised via the “Halt the Salt” campaigns of the 1970s. Accountability for salinity was first
defined for the Murray Darling Basin in the Salinity and Drainage Strategy of 1988.
Since the Prime Minister of Australia the Hon. John Howard drew attention to the impact of
Dryland Salinity in 1999 the scourge of rising salt in soils in productive agricultural areas
(particularly in the Australian States of New South Wales and Western Australia) is becoming
recognised for the catastrophe which, unless it is curtailed, it will visit upon Australia in the
next 50 years.
At a state of equilibrium which is the point at which the watertable can rise no higher, 15
million hectares (150,000 sq kms) will be salt affected on the Australian mainland. This is an
area greater than the land area of Greece (130,800 sq kms). Just at what point in time
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equilibrium will be reached is uncertain but at present rates it could take as little as 20 years
to reach that stage.
The cause of the problem is inappropriate land use stemming from European farming
practices which are unsuited to the climatic and ground conditions in Australia. The root
systems of plants and vegetation are different, so that the replacement of Australian native
vegetation with crops and pastures which have shallower roots and different growth patterns
from native vegetation has led to a rise in the watertable thereby mobilising salts found in
most Australian landscapes, bringing them to or near to the surface.
The rising watertable dissolves the salts in the ground, capillary action draws salts to the
surface and evaporation then concentrates the salts in the surface layers of the soil. The
end result is substantial and irreversible damage to the soil.
To date in Australia the damage has been most evident in the State of Western Australia
which currently has 1.8 million hectares of land affected by dryland salinity. At the point of
equilibrium, 6.1 million hectares will be salt affected. Whilst Western Australia is a huge
State (more than 2,500,000sq kms, much of which is desert) the total salt affected area will
represent 30% of the agricultural land in Western Australia.
In New South Wales, a far smaller State in area than Western Australia, currently 120,000
hectares of land are salt affected, with 7.5 million hectares predicted to be affected at
equilibrium. The fertility of the soils will be destroyed, the ability to grow crops and graze
animals will be reduced and losses for farm properties will be enormous.
THE CAUSE OF DRYLAND SALINITY
Below the surface of the land, lying above an impenetrable layer of rock or clay exists a
naturally occurring watertable. The watertable will rise if rainfall or water introduced via
irrigation does not run off the surface, evaporate or be absorbed by vegetation.
It is when the water saturates the tiny air spaces between soil particles the excess water
seeps down to the watertable and the soil fills up from the bottom (a process known as
“recharge”).
When deep rooted plants with substantial foliage and extensive root systems such as
substantial trees are removed from the land to be replaced by shallow rooted pastures and
annual crops the ability of the land form to "pump out" excess water is reduced. As the
watertable rises, naturally occurring salts in the soils are dissolved and the salts rise in
solution.
Contributors to the rise of the watertable are:-
- clearing of native vegetation
- planting of shallow rooted annual crops
- introduction of water by irrigation
- poor irrigation practices (e.g. over watering and inadequate maintenance of irrigation
channels)
THE IMPACT OF DRYLAND SALINITY
Plants suffer from the effect of the rising watertable in two ways, firstly, salt makes it harder
for plants to take water from the soil and secondly, water logging may occur thereby
effectively drowning plants as the roots cannot obtain the oxygen that they need to "breath"
where the roots are completely surrounded by water.
Salinity directly effects:-
• Agriculture
• Stream salinity
• Aquatic eco-systems and Biodiversity
• Regional and Urban Infrastructure.
And indirectly effects:-
• Land and Property Values
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• Availability of Finance
• Regional Attraction to Industry
LOCAL AND REGIONAL ISSUES
A localised salinity problem resulting from locally high watertables can appear in the following
areas:-
• Directly under irrigated country
• Dry land areas or road sides next to intensive irrigation areas such as summer
cropped or horticultural areas
• Land next to leaking irrigation channels
• Bare ground such as tracks and roadways
• Low lying areas
The local impact arises typically through the local topography. Recharge of ground water
can occur through cleared hill sides then causing salt affected areas to occur in lower lying
valley floors. These are a small scale version of the overall salinity problem occurring on a
regional basis.
The regional salinity problem and ground water movement is more dependant on local
geology (underlying soil and rock structures) than local topography (surface landform). It is
recharge in the upper reaches of the system which then has its effect throughout the
sedimentary basin. Both regional and local impacts of dryland salinity are present in New
South Wales.
Urban development is not immune from the impact of the rising watertable and salt. Millions
of dollars of damage is occurring to infrastructure such as roads and building which crumble
and decay through salt infiltration. Careful consideration needs to be given to local
development which may interfere with natural underground drainage lines as salt may be
mobilised and effect building foundations, roads and drains.
The response to salt in a given area is dependant on an understanding of whether the cause
is localised or has its origin remote from the locality.
The paper considers the options for control of dryland salinity, the response from the 3 tiers
of Government (Federal, State and Local Government) with particular emphasis on the State
of New South Wales which is faced with the most dramatic impact in the "bread basket" of its
agricultural areas.
Identification of the location and depth of the watertable including the connection of the re-
charge and the discharge area both locally and regionally is critical to an understanding of
where the impacts will be felt and where measures which can be taken will have an effect.
The distance between the cause and the effect can be great.
Critical to the response to salinity is vegetation management and crop management along
with the identification of productive uses to which salt effected land may be put.
THE RESPONSE
State and Federal Governments have set the salinity target for the Murray-Darling River
System (the major New South Wales/Victorian/South Australian river system) as drinking
water quality at the town of Morgan in South Australia. The New South Wales Salinity
Strategy then works back up the catchment identifying the target locations.
Measurement of the outcomes is to be undertaken on the basis of "end-of-valley" targets
along with "within-valley" targets moving upstream assessing the impact on assets (towns,
infrastructure productive enterprises etc) and values (wetlands, sensitive ecosystems etc)
with a downstream verification system.
Current salinity levels have been measured at identified ends of valleys for the New South
Wales rivers which flow into the Murray-Darling river system. The Murray-Darling river
system is the interconnection of all the westerly flowing rivers in New South Wales which
incorporates all flows to the west from the Great Dividing Range and into which there are
waters flowing from rivers in the State of Queensland to the north and the State of Victoria to
the south. The Murray River forms the greater part of the border between the States of New
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South Wales and Victoria. Of necessity the response must involve multiple State
Governments and the Commonwealth Government.
It is identified that whilst all rivers in the Murray-Darling river system have salinity levels
which fall within World Health Organisation (WHO) Guidelines for the acceptable taste of
drinking water (800 EC) for 50% of the time, five of the nine target locations approach or
exceed 800 EC for 20% of the time. At Dubbo, the major central New South Wales City
(located on the Macquarie River) salinity levels exceed 800 EC for 6% of the time.
1
Without
a change to the use of natural resources this level is expected to increase to over 80% of the
time by 2100.
2
The estimated cost from excessive salinity levels in lost agricultural
production alone in Australia is $130 million each year and increasing.
3
This figure takes no
account for ecological and social costs.
The Murray-Darling Salinity Audit suggests total costs for that river system of $1 million for
each year for every 5000 hectares of visibly affected land.
4
At equilibrium the cost would
therefore amount to $1.5 billion per annum.
An economic study of urban salinity in Wagga Wagga, the major city in southern inland New
South Wales, (located on the Murrumbidgee River) in 1998 estimated that the net present
value of the cost to that City of the next 30 years (absent preventative measures) would be
$183 million.
5
Salinity is estimated to cause $9 million damage annually to roads and
highways in south western New South Wales alone.
6
Rainfall and the existence of salt in the soil profile are beyond control. Control of salinity
levels is therefore dependent upon the depth at which the underlying watertable can be
maintained which is therefore dependent upon the nature of the activity undertaken within the
recharge areas.
Local groundwater systems may be 1-5 kilometres across and regional groundwater systems
may vary from 10-100 kilometres across.
7
It would be fortuitous for the recharge and
discharge areas to be within the one property ownership in a local groundwater system and
unimaginable (even in the broad expanses of outback New South Wales) for the recharge
and discharge areas to be in the one property ownership in a regional groundwater system.
Intervention by government will thereby be required to create and to enforce a regime which
will have the farmer in the recharge area manage operations on that property to keep the
watertable at a level which will not cause adverse impacts downstream in the groundwater
system (and where there is discharge into a river system, to that river system).
LEGISLATIVE SYSTEM
Australia has a Parliamentary Democracy based on the liberal democratic tradition. The
location of land uses sympathetic to the environment and to the population in Australia is
governed by a legislated system of land use planning.
Australia is governed by a National Government (the Commonwealth) with specific powers
- New South Wales Department of Land and Water Conservation (2000) NSW Salinity Strategy, Sydney.
- New South Wales Department of Land and Water Conservation (1999) Salinity Predictions for NSW Rivers within the Murray-Darling Basin CNR 99.048. Sydney.
- Prime Minister's Science Engineering and Innovation Council (1999) Dry Land Salinity and its Impact on Rural Industries and the Landscape, Occasional Paper No. 1, Department of Industry Science and Resources. Canberra.
- Murray-Darling Basin Ministerial Council (1999) The Salinity Audit of the Murray-Darling Basin: A 100 Year Perspective, Murray-Darling Basin Commission. Canberra.
- Hill, C. (2000) The Wagga Wagga Urban Salinity Study, Economic Evaluation of Options, Department of Land and Water Conservation Socio-Economic Assessment Unit Wagga Wagga.
- Prime Minister's Science Engineering and Innovation Council (1999) Dry Land Salinity and its Impact on Rural Industries and the Landscape, Occasional Paper No. 1, Department of Industry Science and Resources. Canberra.
- Coram, J. Ed (1998) National Classification of Catchments for Land and River Salinity Control, Water and Salinity Issues in Agroforestry Number 3. Rural Industries Research and Development Corporation Publication No. 98/78 Canberra.
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enshrined in a Constitution. The remaining or reserve powers are held by the six States
which came together to form the Commonwealth of Australia (there are in addition two
mainland Territories the governmental systems of which are not relevant for the purposes of
this paper).
Within the State of New South Wales there is a third tier of government known as Local
Government which exists by virtue of State legislation under the provisions of the Local
Government Act 1993. There are presently 152 Local Councils set up pursuant to the Local
Government Act 1993 which are vested with the primary land use planning role set up under
the Environmental Planning and Assessment Act NSW 1979 ("EP&A Act") under which the
various land use planning instruments are set up. The hierarchy of environmental planning
instruments includes State Environmental Planning Policies ("SEPP"), Regional
Environmental Plans ("REP") and Local Environmental Plans ("LEP"), with the LEP being the
principal environmental planning tool for each of the councils.
LEPs identify various zonings for land use, traditionally being rural, residential, commercial,
industrial, special uses, recreational and environmental protection. A table or matrix of uses
which are prohibited and permissible either with or without development consent of the
council determines the land use in a locality and specific provisions are then applied by the
LEP or by supporting Development Control Plans ("DCP"). Where a particular land use is
unsuited to the locality it is likely to have the land zoned to prohibit that use, otherwise the
land use will be permissible with or without the need for development consent from the
council. Where development consent is required, conditions which must be complied with
are invariably attached to the consent. Compliance with those conditions is mandatory and
enforceable with civil and criminal remedies.
The development consent (of which the conditions form part) is not specific to the individual
to whom it was granted, but is a right which runs with the title to the land. For
environmentally sensitive land and for land uses with potentially significant environmental
impact, a stringent regime of environmental assessment is required where development
consent is required by an environmental planning instrument.
LEPs are the product of local planning which are approved at the State level and made by
the State Minister for Planning signing them into existence. Provisions are in place in the
EP&A Act for LEPs to cross Local Government boundaries. For a State planning issue (and
it may be encountered at a regional level) the Minister for Planning could introduce a SEPP
which generally has the effect of overriding inconsistent provisions in an LEP although its
implementation is generally administered at a Local Council level.
PLANNING CONTROL
The use of land for agriculture in a rural zone is generally permissible without the need to
obtain development consent. Agriculture is generally defined to include all manner of
agricultural uses. Where control over intensive agriculture appears in an LEP Intensive
Agriculture is, generally, narrowly defined. With the exception of a SEPP to control intensive
agriculture, the definition of which is narrow, there is no SEPP to control agriculture.
The consequence is that the vast amount of agricultural land, under which lies the salt profile
and the watertable and which incorporates the recharge and discharge areas, is uncontrolled
by a system of land use planning. Agriculture being permissible without the need for consent
is uncontrolled as to clearing for agricultural purposes, the location of infrastructure, cropping
and crop watering. Without the need for development consent agriculture cannot be
conditioned as to its operation.
The New South Wales Salinity Strategy identifies that partnerships of relevant stakeholders
are to be responsible for the development of regional vegetation management plans, water
management plans and such similar plans as may be developed by the States,
privatised/corporatised irrigation districts. Local Government is identified with respect to its
role with LEPs and DCPs. It would appear that the Strategy has therefore identified
(correctly in my opinion) that the practical application of planning resides within the expertise
of Local Government. Notably absent from the Strategy is involvement of the Department of
Planning and the ability for the Minister to effect sweeping change by the application of a
SEPP.
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Salinity is not an issue which is discrete to an individual farming enterprise and therefore the
individual land owner (except in the most localised of salinity issues) cannot resolve the
problem. In those circumstances the individual standing alone is, not only not interested to
be the catalyst for change, but is powerless to do so.
New and improved farming systems and land management practices more suited to
Australia's unique landscapes must be developed and the potential to farm native plants and
animals must be considered. A movement to other more salt tolerant plant species will be
necessary where the impact of salinity is now irreversible.
Local Government is the tier of government which is closest and most accessible to the
individual land owner. Council has the general responsibility for land use in its area and the
powers are already in place under the EP&A Act for environmental assessment where
development consent is required for land use.
The background to the absence of regulation of agricultural land use appears to be in the
historical European settlement of Australia. Development of land by European settlers,
particularly west of the Great Dividing Range in New South Wales (the "Blue Mountains
area") involved land grants to reward settlers (and some convicts), squatting and the more
recent phenomenon of Grants of Land to soldiers returning to Australia after World War II.
The philosophy involved challenging people to develop agricultural pursuits in a harsh
climate hence it was inconsistent to constrain the manner in which they would make their
land use decisions.
The continued development of agriculture in a sustainable way is now dependent upon the
way in which the land use is managed. Such trade offs as may be required between land
holdings and land uses will require co-operation through the catchment area. Just as a
location unsuited to industrial development will be zoned to prohibit or to control such land
use, so should agricultural use be controlled by proper land use planning not to
unreasonably interfere with the environment.
Proper land use planning is the key to management of salinity issues.
CONCLUSION
Unconstrained agricultural development with methods unsuited to the landscape has
mobilised salt which is resident in the soil profile. Scientific and engineering based solutions
along with crop management plans are in various stages of development and require to be
implemented across a broad landscape. Environmental degradation will continue unless a
concerted and co-operative approach to resolve a problem which is unconstrained by
Council or State borders. All three tiers of government must be involved.
In a system where land is privately owned, a legislated land use planning scheme is the
mechanism to inspire and if necessary, to coerce a change in natural resource management.
A sophisticated land use planning regime is in place in New South Wales. Political, cultural
and historical reluctance to allow land use planning to implement the scientific, engineering
and management responses must be set aside.
