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Introduction to the Salinity Information Package
The
material presented in this Salinity Information Package (SIP) is
intended as a ‘work book’ of modern reference material
particularly aimed at those working in dryland salinity planning
and extension in the
Murray-Darling Basin. It provides a stepwise understanding of the
complex relationships between land use, land management, landscapes,
groundwater flow systems, catchment communities, industries, institutions,
and social and economic factors that influence salinity management.
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A1 The causes and risk of dryland salinity
Dryland salinity (sometimes referred to as secondary salinity) throughout
the Murray-Darling Basin results from changes in the water balance
of landscapes following the removal of native vegetation and the
introduction of European agricultural practices, most significantly
the adoption of shallow rooted annual crops and pastures.
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A2A Dryland salinity processes in the Murray Basin
Dryland salinity (sometimes referred to as secondary salinity) throughout
the Murray-Darling Basin results from changes in the water balance
of landscapes following the removal of native vegetation and the
introduction of European agricultural practices, most significantly
the adoption of shallow rooted annual crops and pastures.
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A2B Dryland salinity processes in the Great Artesian and Darling
Basins
The
processes causing dryland salinity in the Murray-Darling Basin (MDB)
involve the movement of salt and groundwater through the geomorphic
and geologic units that comprise the Basin’s landforms and
aquifers. No single landscape or groundwater process causes all
salinity throughout the Basin. Rather, a suite of salinity processes
exists.
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A3 The extent and impact of dryland salinity
The
extent and impact of dryland salinity (often referred to as secondary
salinity) in the Murray-Darling Basin is not known with great certainty.
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A4 Understanding dryland salinity management
The
manifestation of salinity in each region of the Basin is linked
intimately to the groundwater
processes prevailing within that region, and relationships with
regional landscapes. Only when these relationships are understood
can informed salinity management planning occur.
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B1 Salt affected soils
In most instances dryland salinity is caused by saline groundwater
seeping to the surface of the land. It
impacts on soil quality and water resources, depleting their utility
and environmental value. Salinity is usually evident after watertables
reach within two metres of the surface when shallow saline groundwater,
drawn up by capillary action, is further concentrated by evaporation.
This may take a decade or two.
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B2 Salt affected streams and other water bodies
As
well as affecting soil, dryland salting also affects the salinity
of surface waterbodies including streams, rivers, lakes, wetlands
and farm dams. The Murray-Darling Basin Commission (1999) suggests
that within the next 50 years dryland salinity will have the potential
to raise the salinity of the River Murray to the point where it
will be unsuitable as a water supply for Adelaide, and may severely
impact irrigation based industries.
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B3 Salt-affected natural ecosystems
An
increase in water salinity presents a range of problems for plants
and animals that are adapted
to the natural environments of the Murray-Darling Basin. The most
important impact of saline water is upon body fluid salt concentrations.
Animals and plants maintain the salt concentration in their body
fluids within a fairly narrow range for the physiological functions
essential to life to occur effectively. Studies of animals and plants
that have adapted to living in saline conditions show that they
possess a number of common characteristics which maintain a fairly
constant salt concentration in their body fluids. Animals and plants
without these advantages are vulnerable to increases in salt in
their environment. It is the rapid change in water quality that
can result in the collapse of aquatic and terrestrial ecosystems.
The salinity ranges within which various wetland animal species
survive are provided in the table below.
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B4 Salt-affected infrastructure
The
term ‘salt affected infrastructure’ used in this information
sheet relates to non-farm and nonecological
impacts arising from the development of dryland salinity. These
comprise:
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B5 Quantify the extent and impact of dryland salinity
Understanding
the extent, impact and landscape context of salinity damage is an
essential part of
gathering information for planning and management. Assessing the
current extent and cost of salinity, understanding who and what
is affected, appreciating who bears the cost, sorting out who contributes
to the problem, and knowing who benefits from salinity management;
these are all facets of the knowledge required for adequate regional
planning. This information must be acquired to ensure wise expenditure
under appropriate cost sharing arrangements. It is not enough to
simply recognise salinity; it must be quantified in terms of costs,
benefits and risks in the future, under current and alternative
arrangement.
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B6 How to assess the costs of dryland salinity?
Despite
dryland salinity being recognised as a significant issue within
the Murray-Darling Basin, there are few estimates of the full cost
of dryland salinity impacts. Quantifying the extent and cost of
the problem provides information critical for developing salinity
management plans and setting priorities and targets.
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C1 Assessing salinity risk from groundwater trends
The
main process we need to be aware of in the development of dryland
salinity is the general rise
of watertables in the landscape, which draws saline water into the
root zone of plants and eventually to the soil surface. Therefore,
observing groundwater movement at a catchment or subcatchment level
is a straightforward way to assess the risk of dryland salinity.
The fact that groundwater systems are slow and dynamic must always
be taken into account. Short-term trends may defy longer-term trends,
particularly in response to climate variability.
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C2 Assessing salinity risk from streamflow and water quality
Rising
groundwater increases saline groundwater discharge and the salinity
of streams rise as more salt is exported from catchments. The risks
associated with increased stream salinity are imposed on downstream
users and the environment. Understanding the risks of increased
stream salinity is a matter of understanding how the salts are generated,
how the streams are regulated, where the salts end up, and where
and how they are accumulating downstream.
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C3 Assessing salinity risk from groundwater discharge
Soil
salinity is a reflection of saline groundwater discharging in the
landscape. As watertables rise and groundwaters progressively intersect
the soil surface the area affected by dryland salinity is seen to
expand. The rate of expansion will be rapid at first, but will slow
down over time as the volumes of discharging groundwater and groundwater
supplied by the aquifer reach equilibrium.
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C4 Inferring salinity risk from catchment characteristics
There
is a good understanding of the range of processes driving dryland
salinity. This knowledge has been gained largely in a few well studied
and documented catchments. Recently, a large effort has been made
to extrapolate this understanding across the whole of Australia.
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C5 Estimating salinity risk from water balance models
Water
balance models are tools that frame dryland salinity issues. They
help us understand and quantify water moving through soils or landscapes
and causing dryland salinity. There are many different types of
models ranging from ‘back of the envelope’ calculations
that experienced hydrogeologists and soil scientists use, through
to very sophisticated numerical computer packages.
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D1 Introducing groundwater flow systems (salinity provinces)
The
fundamental cause of dryland salinity is a shift in the water balance
following the removal of native vegetation for agriculture. The
processes that influence dryland salinity, however, vary from place
to place in accordance with landscapes and groundwater aquifers.
These, in turn, reflect regional geology and geomorphology.
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D2 Groundwater recharge
There
are several different processes by which groundwater recharge may
occur. Water may simply leak through the base or banks of rivers
and streams, or from wetlands, dams and reservoirs, and percolate
to the saturated zone within underlying aquifers.
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D3 Groundwater discharge
Saline
groundwater discharge takes several different forms. It discharges
directly through the floor or banks of a stream (baseflow), affecting
stream salinity, or may discharge as a saline seep, causing soil
salinity. Soil salting also raises salinity in adjacent streams
as salt is washed off affected areas by rainfall.
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E1 Catchment planning and biological management options
The
range of types of dryland salinity problems in the Murray-Darling
Basin is considerable. The key to developing sensible and feasible
dryland salinity management strategies in the Murray-Darling Basin
lies with understanding how landscapes and groundwater processes
function to cause these salinity problems.
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E2 Trees in salinity management
Decisions
over how to best manage dryland salinity should always be made on
the basis of landscape attributes, land capability, the nature and
scale of groundwater flow systems and the feasibility of salinity
‘mitigation’ vs salinity ‘management’ (see Information
Sheet E2).
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E3 Productive uses of saline resources
As
saline groundwater continues to rise in dryland catchments of the
Murray-Darling Basin we are becoming increasingly aware that salinity
will continue to expand over the coming decades in spite of best
efforts to contain it. Large areas of saline affected land will
become unsuitable for traditional agriculture, and the quality some
water resources will further decline. Therefore, some regions will
determine ‘living with salt’ to be the most effective
salinity management strategy.
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E4 Engineering strategies
Under
some circumstances engineering approaches may be appropriate for
managing dryland salinity.
However, the high cost of the technology, together with a range
of technical difficulties, often restricts engineering applications
to those situations where major assets must be protected. Adopting
engineering strategies to avoid dryland salinity is seldom cost
effective in conventional dryland agriculture situations.
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E5 Assessing costs and benefits
Finance
to repair salinity damage, whether privately or publicly sourced,
is normally very limited. Possible
investments need to be ranked in order to make the best decisions
about which investments to make. Cost–benefit analysis is often
used to assist in determining these investment rankings including
who should give and receive the benefits. This process counts all
the costs and all the benefits of each option, using a number of
assessment methods, to determine which is best. Costs and benefits
are measured relative to a ‘do nothing’ or ‘base’
scenario.
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E6 Cost sharing: Who pays and who should pay?
Many
individuals, community groups and organisations are already contributing
considerable time, effort, capital and cash to reducing salinity
damage in the Murray-Darling Basin. It is unlikely that there will
be any new, as-yet-unidentified sources of funds in the foreseeable
future, so increased funding will only come from even greater contributions
from these sources.
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E7 Regional development opportunities— building new industries
around salinity management
There
is an emerging view in Australia that we pursue regional development
pathways which improve economic return and social equity, while
ensuring that Australia’s land and water resources can sustain
both natural ecosystems and forms of human use and management.
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E8 Resources required to develop and implement strategies
All
too often the term ‘resources’ in today’s world is
equated with money. This is understandable,
because financial support is essential to developing and implementing
dryland salinity strategies, but it is equally important to have
a strong sense of what else is required before launching into a
major quest for financial support.
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F1A Identifying State and Commonwealth agencies
Within State and Commonwealth governments there are numerous key agencies, committees, councils and research institutions that support nationally coordinated action against dryland salinity through policy development, planning, R&D and State and regional program funding. It is important to understand the roles of these key institutions in order to appreciate the mechanisms of policy development and the
origin of national or Basin-wide programs that support the activities of regional communities.
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F1B Working with State and Commonwealth agencies
Tackling the complex institutional and legal framework of Australia is a daunting proposition for most people. Three tiers of government and any number of agencies, committees and councils generate policies and plans that impact upon the management of dryland salinity. An array of intersecting research and development institutions continuously feeds new technical, social and economic information into an ever-evolving policy and regulatory environment.
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F2 Working with regional catchment communities
Working
with regional communities in attempting to attain regional dryland
salinity management
involves activities far broader than simply working with affected
landholders. The task involves a
much broader range of stakeholders, and a much greater effort of
contributing to continuous improvements in regional understanding
and management of the issue, including the development of innovative
regional policies and initiatives to best address it.
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F3 Working with local government
More
than 400 urban and rural local government areas are currently affected
by dryland salinity, Australia-wide. It is estimated that dryland
salinity costs the nation more than $100 million per annum from
damage to infrastructure alone. A substantial proportion of these
costs are borne by local government associated with damage to infrastructure
(e.g. roads, bridges, footpaths, parks, recreational facilities
and drainage systems), damage to natural assets, reduction in property
values, decrease in drinking water quality, and increase in the
risk of flooding.
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F4 Working with industries
Working
towards the objective of managing dryland salinity involves much
more than working with farmers, farming communities, and landcare
groups. Salinity is an issue that affects the broader community
through the impact that it has on water resources and the environment,
and infrastructure.
This impact motivates the three levels of government to be involved
in the salinity issue.
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G1 Monitoring the adoption of salinity strategies
In
recent years catchment communities have been bombarded with strategies
and farming systems that
will hopefully contribute to the reduction, or at least management,
of increasingly saline conditions in much of Australia’s soil
and water resources. If we are to determine with any confidence
which strategies are working, which are being taken up by land managers
and which are too unpalatable or impractical for widespread use,
we need monitoring systems in place.
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G2 Managing the effectiveness of dryland salinity management strategies
Dryland
salinity management strategies in the Murray-Darling Basin generally
comprise the following elements:
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G3A Benchmarking dryland salinity
It
is often said that planning is a three step process
involving three simple questions:
• Where do I want to go?
• How do I get there?
• How do I know when I am where I wanted to be?
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G3B End-of-valley targets
Benchmarking
the impact of salinity on water resources is a difficult task (as
described in
Information Sheet G3). However, through evolving government policies
and planning, end-of-valley targets have emerged as a key benchmarking
tool for monitoring the amount of salt exported from catchments
within the Murray-Darling Basin.
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G4 Establishing regional databases
Adatabase
is simply a system for storing and retrieving information. Most
databases are now
organised within computers, and may range from simple spreadsheets
to dedicated software programs that link to sophisticated computer-based
geographic information systems (GIS). These are capable of analysing
and representing many different forms of information collected within
a catchment or region.
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H1 Analysing regional data and reporting trends
A
great deal is known of the landscape processes that cause dryland
salinity in the areas most at risk
within the Murray-Darling Basin, but much less is known about how
best to manage the issue. Moreover, as our understanding improves
we are coming to realise that many of the farming practice modifications
that once promised to control salinity can no longer be considered
effective and appropriate.
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H2 Successes and failures — working through the issues
Given
that this is the last in this series of information sheets it is
appropriate to reflect upon the philosophy of salinity management
for rural communities in the Murray-Darling Basin, and indeed throughout
Australia.
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O1 Introduction to the Salinity Information Package
The
material presented in this Salinity Information Package (SIP) is
intended as a ‘work book’ of modern
reference material particularly aimed at those working in dryland
salinity planning and extension in the Murray-Darling Basin. It
provides a stepwise understanding of the complex relationships between
land
use, land management, landscapes, groundwater flow systems, catchment
communities, industries, institutions, and social and economic factors
that influence salinity management.
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01 Information steps in the Tools extension framework
INFORMATION
STEP A
Understanding Dryland Salinity
A1 The causes and risks of dryland salinity
A2a Dryland salinity processes in the Murray Basin
A2b Dryland salinity in the Great Artesian and Darling Basins
A3 The extent and impact of dryland salinity
A4 Understanding of dryland salinity management
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O3 Keyword index to the Tools information package
Agriculture
A1, B1, C4, D1, E1, E2, E3, E4, E7, F1b, F5, H1
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04 Glossary
Agronomy
The applied aspects of both soil science and the several plant sciences,
often limited to applied plant sciences dealing with crops.
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