RIVER RESEARCH AND APPLICATIONS
River Res. Applic. 19: 377–395 (2003)
Published online in Wiley InterScience
(www.interscience.wiley.com). DOI: 10.1002/rra.745
FLOW RESTORATION AND PROTECTION IN AUSTRALIAN RIVERS
ANGELA H. ARTHINGTONa,b* and BRADLEY J. PUSEYb
a
b
Co-operative Research Centre for Freshwater Ecology and Management, Centre for Catchment and In-Stream Research,
Griffith University, Nathan, Brisbane, Queensland 4111, Australia
Co-operative Research Centre for Tropical Rainforest Ecology and Management, Centre for Catchment and In-Stream Research,
Griffith University, Nathan, Brisbane, Queensland 4111, Australia
ABSTRACT
Since 1857 new Australians have constructed many thousands of weirs (3600 in the Murray–Darling Basin alone) and floodplain levee banks, 446 large dams (>10 m crest height) and over 50 intra- and inter-basin water transfer schemes to secure water
supplies for human use. Flow regulation has changed the hydrology of major rivers on three temporal sales–the flood pulse
(days to weeks), flow history (weeks to years) and the long-term statistical pattern of flows, or flow regime (decades or longer).
The regulation of river flows is widely acknowledged as a major cause of deteriorating conditions in many Australian river and
floodplain ecosystems. In response to mounting environmental concerns, all states, territories and the Commonwealth Government have committed the nation to the principles of ecologically sustainable development and a process of national water
reform. Rivers and wetlands are now recognized as legitimate ‘users’ of water, and jurisdictions must provide water allocations
to sustain and where necessary restore ecological processes and the biodiversity of water-dependent ecosystems. Progress in the
protection and restoration of river and wetland water regimes has been significant, with over half of mainland aquatic systems
designated to receive water allocations of some sort. However, exactly how much water they will receive or retain is unclear
from the data available. Moreover, the ecological outcomes and benefits of water allocations are not yet apparent in most aquatic
ecosystems, with the exception of certain waterbird breeding events, the disruption of algal blooms in weirs and improved fish
passage. After reviewing these issues, this paper addresses two vital questions: How much water does a river need? and How can
this water be clawed back from other users? Studies conducted to date in Queensland rivers suggest that around 80–92% of
natural mean annual flow (and other ecologically relevant hydrological indicators) may be needed to maintain a low risk of
environmental degradation. In the Top End of the Northern Territory, some rivers are maintained at 80% of their natural flow,
whereas two-thirds of various flow indicators has been proposed as the restoration target for the River Murray, and 28% of
natural mean annual flow has been negotiated for the Snowy River in Victoria. To validate these estimates, ecologists are seeking opportunities to turn river restoration projects into long-term hypothesis-driven experiments in ecological restoration, and
the funding, time and institutional support to do so. The paper ends with some suggestions to advance the water reforms and
achieve higher levels of water allocation for the environment.Copyright # 2003 John Wiley & Sons, Ltd.
key words: Australia; flow restoration; environmental flows; flow regulation; water reforms; experimental research; water pricing, water trading
INTRODUCTION
In honour of our late colleague, Professor W.D. (Bill) Williams, it is appropriate to begin this paper about flow protection and restoration in Australia with two observations from his early texts on the ecology of Australian inland waters.
The direct effects of man on the inland aquatic environment have undoubtedly had important consequences
for the distribution and abundance of much of the aquatic biota, consequences which, moreover, are probably
still a long way from the full attainment (Bayly and Williams, 1973: Inland Waters and their Ecology).
Almost every Australian lake, river, stream and pond now bears the imprint of man, or will shortly do so. And,
like it or not, the future of the Australian inland aquatic environment is for man to determine (Williams, 1980:
An Ecological Basis for Water Resource Management).
Two decades later, Boulton and Brock (1999) concluded their text (Australian Freshwater Ecology: Processes
and Management) with an overview of water issues, commenting:
*Correspondence to: A. H. Arthington, CCISR, Griffith University, Nathan, Brisbane, Queensland 4111, Australia.
E-mail: a.arthington@griffith.edu.au
Copyright # 2003 John Wiley & Sons, Ltd.
Received 28 April 2002
Revised 10 December 2002
Accepted 16 December 2002
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A. H. ARTHINGTON AND B. J. PUSEY
In Australia, there has been a shift in emphasis from concern largely about water quantity and supply for
humans’ needs (engineering solutions) to protecting water quality and sustaining natural ecosystems (ecological solutions). We now recognise the central role of water regime in most wetland processes . . . .
Today, in 2003, Australians have a much keener appreciation of the remarkable features of the continent, the
scarcity, fragility and value of its freshwater ecosystems and the importance of maintaining and restoring river and
wetland water regimes. Before reviewing progress with flow protection and restoration in Australia, it is important
to appreciate the extreme climatic variability characterizing much of the continent, and how challenging their new
conditions were for European colonists accustomed to seasonal variability in rainfall but unacquainted with a climate that could swing between drought in one year and floods the next. As a consequence of the dire need for
reliability of water supplies and food, many weirs, dams and levee banks were constructed and river flows were
regulated by these structures or modified by water abstraction and diversions. The legacy from these and other
interventions in rivers and floodplain wetlands is the modification of water regimes and severe ecological impacts.
This paper gives a brief summary of these impacts and an introduction to the wider literature on the state of
Australia’s inland waters. In 1993, pressured by growing environmental, social and economic concerns, the Commonwealth Government and all Australian states and territories committed the country to the principles of ecologically sustainable development and a wide-ranging programme of water reforms, including economic
restructuring of the water industry and formal allocations of water to the environment. Rivers and wetlands have
been recognized as legitimate ‘users’ of water, and jurisdictions have been defining and implementing water allocations to sustain and restore ecological processes and the biodiversity of water-dependent ecosystems. Progress in
the protection and restoration of river water regimes is recounted in this paper, through which run two vital questions: How much water does a river need? and How can this water be clawed back from other users?
AUSTRALIA’S CLIMATE AND HYDROLOGY
Australia (Figure 1) is a relatively small (8.42 106 km2) continent lying between latitudes 10 410 S (Cape York)
and 43 390 S (southern Tasmania), a land of extensive plains and plateaux with only 2% of the land area above
Figure 1. Map of Australia showing locations of major rivers mentioned in the text
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AUSTRALIAN RIVERS
1000 m a.s.l and 59% lying between 200 m and 1000 m (Jennings and Mabbutt, 1986). It lies in the mid-latitude
high pressure belt of the southern hemisphere and its climate is dominated by eastward moving anticyclonic cells
with a low moisture content (Nix, 1981). Australia is the driest inhabited continent, receiving on average only
455 mm of rainfall annually; 66% of the continent gets <500 mm of annual rainfall (Nix, 1981). Evapotranspiration losses are high and mean annual runoff is only 57 mm, yielding the world’s lowest percentage of rainfall as
runoff (mean of 12% compared to 33% for North America). Rainfall and runoff are not only lower in Australia than
on any other continent but also more variable, both spatially and temporally. Spatial variations in runoff separate
the continent into two distinct areas, a humid coastline and an arid interior, with the greatest proportion of total
runoff occurring in the northern and northeastern coastal areas (88% from only 26% of the land area), and the least
recorded in arid and semi-arid regions (75% of the continent receives <12.5 mm of annual runoff). Extreme temporal variations in runoff are also characteristic of much, but not all of Australia (Finlayson and McMahon, 1998;
Smith, 1998). According to a range of hydrological indicators, arid-zone rivers such as Cooper Creek and the Diamantina River have the most variable flow regimes on Earth (Puckridge et al., 1998).
Groundwater plays an important role in Australia’s water budget. Recent assessments suggest that some
25 780 Gl of rainwater finds its way into groundwater aquifers each year (SEAC, 1996). Groundwater, emerging
at or near the surface, provides the base flows that sustain life in many arid-zone and other rivers during dry periods,
supplies Australia’s unique mound springs and cave systems, as well as sustaining many types of plant community.
Australia’s climate is changing under the influence of global warming. Studies by the Commonwealth Scientific
and Industrial Research Organisation (CSIRO) suggest that annual average temperatures will rise by 1–6 C over
most of Australia by 2070 (Whetton, 2001). Warmer conditions will lead to increased evaporation rates, decreased
moisture, increased moisture stress, and either wetter or drier conditions, with significant effects on the number of
flood and drought years. Daily rainfall variability and extreme events will change but not uniformly across the
continent, leading to both increases and decreases in stream flows.
FLOW REGULATION AND ITS ECOLOGICAL CONSEQUENCES IN AUSTRALIA
The uneven spatial distribution and extreme temporal variability of surface and groundwater supplies in Australia
have played a pivotal role in its settlement and development. Water control schemes were constructed almost
immediately upon European colonization to secure reliable water supplies for settlements, mining and irrigated
agriculture. From 1857 to the present, new Australians have constructed a multitude of flow regulation structures,
including many thousands of weirs (3600 in the Murray–Darling Basin alone), locks and floodplain levee banks,
446 large dams (>10 m crest height) and over 50 intra- and inter- basin water transfer schemes. Australia now has
the highest per capita water storage capacity in the world (8.8 107 Ml or 106 l), with 79% of this stored water used
for irrigation purposes, the highest proportional usage of all OECD countries (SEAC, 1996). Most of this water is
held in a few very large storages, the ten largest holding about 50% of total capacity. Details of dams and other
interventions in rivers and floodplain wetlands can be found in Kingsford (2000).
Australia’s legacy from the era of dam construction and floodplain modifications is highly modified flow
regimes and degraded rivers. Flow regulation has changed the hydrology of rivers on three scales of temporal variation (Walker et al., 1995): the flood pulse (days to weeks), flow history (weeks to years) and the long-term statistical pattern of flows, or flow regime (decades or longer). Total river flows and their temporal patterns are
fundamentally altered in many of the continent’s great rivers, including the River Murray, the major headwater
tributaries of the Darling in New South Wales, the Burdekin, Fitzroy, Proserpine, Pioneer, Burnett, Mary, Brisbane
and Logan rivers of Queensland, many coastal rivers in New South Wales, the Snowy River in Victoria, the Ord
River in Western Australia, the Gordon and other Tasmanian rivers, as well as many small stream systems throughout the continent. Within-channel flows have been markedly reduced in streams and rivers, seasonal flow patterns
have been lost or inverted and many floodplains and wetlands are much less frequently flooded than before dam
construction, whereas some wetlands and temporary streams that naturally dried periodically are now permanently
wet, or have lost their natural seasonal pattern of wet and drier months (Walker, 1985; Walker and Thoms, 1993;
Gehrke et al., 1995; Gippel and Stewardson, 1995; Maheshwari et al., 1995; Kingsford, 2000; Sheldon et al., 2000;
Thoms and Sheldon, 2000). The hydrological variability that typifies the natural flow regime of most Australian
rivers (Pusey et al., 1993, 1995; Lake, 1995; Pusey and Arthington, 1996; Finlayson and McMahon, 1998;
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Puckridge et al., 1998), and the water regimes of many wetlands have been altered at a range of temporal and
spatial scales (Maheshwari et al., 1995; Walker et al., 1995; Arthington et al., 2000; Brizga, 2000; Kingsford,
2000; Thoms and Sheldon, 2000).
Flow regulation is widely acknowledged to be a major cause of deteriorating conditions in many Australian river
and floodplain ecosystems (Cullen and Lake, 1995; Lake, 1995; Walker, 1985; Walker et al., 1995; Kingsford,
2000; Bunn and Arthington, 2002). Ecological changes in regulated river systems include massive loss of wetlands
(90% of floodplain wetlands in the Murray–Darling Basin, 50% of coastal wetlands in New South Wales and 75%
of wetlands on the Swan Coastal Plain in southwest Western Australia; Bunn, 1999; Kingsford, 2000), decline of
riparian forests (Kingsford, 2000; Leslie, 2001), invasion of dewatered river channels and wetlands by vegetation
(Bren, 1992), changes in aquatic plant community structure in regulated river reaches and weirs (Blanch et al.,
2001; Mackay et al., 2001), population and species diversity declines of invertebrates, fish and waterbirds (Harris,
1984; Doeg et al., 1987; Gehrke et al., 1995; Kingsford, 2000; Quinn et al., 2000) and several invertebrate extinctions (Sheldon and Walker, 1997). Seven lacustrine invertebrates disappeared when Lake Pedder in Tasmania was
flooded as part of a hydropower scheme, and leeches collected from River Murray wetlands by Victorian hospitals
at up to 30 000 per annum were seldom seen after the 1970s (Kingsford, 2000). More conspicuous impacts of flow
regulation have been massive blooms of toxic cyanobacteria in storages and rivers, most notably the 1000 km long
bloom in the Barwon–Darling River in 1991, so severe as to necessitate the declaration of a state of emergency and
trucking of water to rural homesteads (Bowling and Baker, 1996). Australia’s regulated rivers have also been prone
to invasions of exotic species of plants such as water hyacinth (Eichhornia crassipes), Hymenachne, willows (Salix
spp.), and fish (Arthington et al., 1990), especially carp (Cyprinus carpio; Gehrke et al., 1995) and tilapia (Arthington and Blühdorn, 1994). As Cullen and Lake (1995) so aptly state, we have degraded our rivers and wetlands in
ways that prevent them from sustaining natural aquatic ecosystems and their high levels of endemicity, and are
replacing them with simplified systems of lower diversity and many exotic species that will be much less useful
to humans in the future.
Bunn and Arthington (2002) review Australian examples of four key flow-related processes underlying the
decline of aquatic biodiversity in regulated rivers (habitat alterations and loss, disruption of life history processes
and recruitment, loss of longitudinal and lateral connectivity, and susceptibility to invasions by exotic species). All
of these processes combine to alter the natural distributions of species and the dynamics of aquatic populations, as
well as aquatic community structure, ecological interactions (parasitism, competition and predation) and ultimately, food web structure and energy flow, as demonstrated so often in other parts of the world (Sparks, 1995;
Ward and Stanford, 1995; Lundqvist, 1998; Ward et al., 2001; Naiman et al., 2002).
WATER REFORM IN AUSTRALIA
Scientists and environmental groups began agitating about the impacts of large dams and the degradation of rivers
in the early 1970s when remote Lake Pedder was flooded and the wild rivers of Tasmania were threatened by
hydropower developments. At that time, the management objective was to provide ‘maximum supplies with minimum wastage of water’ (Water Conservation and Irrigation Commission, 1971), and a wastewater mentality prevailed. Australia’s large catchments were termed ‘drainage divisions’, rivers were said to supply ‘effluent’ creeks
and water flows to floodplains, wetlands, aquifers or to the sea were called ‘surplus flows’ and were regarded as
‘wasted’. Twenty years later Australia adopted the National Strategy for Ecologically Sustainable Development,
and in 1994, in response to growing environmental concerns and the need for economic restructuring of the water
industry, all three tiers of government in Australian (Federal or Commonwealth, State/Territory and Local) committed to a process of national water reform. The Council of Australian Governments (CoAG), representing all
governments, drove the water reform process, agreeing to ‘implement comprehensive systems of water allocations
and entitlements backed by separation of water property rights from land title and clear specification of entitlements in terms of ownership, volume, reliability, transferability and, if appropriate, quality’ (CoAG Communique,
25 February 1994, Hobart, Attachment A Water Resource Policy, Item 4a). Underlying the CoAG water reforms is
the expectation that implementation of water pricing, trading and greater efficiency of use will lead to improvements in land and water management and in all forms of environmental quality, particularly the ecological integrity
of river and floodplain ecosystems (Smith, 1998).
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To give policy guidance to jurisdictions and water managers responsible for implementing the reforms, 12
National Principles for the Provision of Water for Ecosystems (ARMCANZ, ANZECC, 1996) were formulated
(Table I). The basic premise of the principles is that rivers and wetlands are legitimate ‘users’ of water and that
the provision of water allocations is critically important to ecological sustainability. The goal of the principles is ‘to
sustain and where necessary restore ecological processes and biodiversity of water dependent ecosystems’ by
means of environmental water allocations that are legally recognized and founded on the best scientific information available (ARMCANZ, ANZECC, 1996, p. 5). The principles further require that all aspects of water management must consider the implications for water-dependent ecosystems; monitoring systems must be established to
assess the ecological outcomes of water allocations, and they must be amenable to adjustment on the basis of new
knowledge and understanding gained through monitoring and research.
Under the Australian Constitution, State and Territory Governments have responsibility for the management of
the surface and groundwater resources of the continent (except for areas of Commonwealth land). Thus to implement the CoAG water reforms, all jurisdictions have had to introduce new water legislation and make adjustments
to policy and institutional structures enabling consideration of the provision of environmental water allocations.
Early histories of these developments can be found in Allan and Lovett (1996) and Smith (1998). They have led to
diverse legislative and institutional arrangements, accompanied by regional and quite variable approaches to the
determination of water allocations for the environment, reflecting different geographic, climatic and ecological
conditions, past policies, water management practices and commitments to water users, and scientific as well as
methodological developments.
ENVIRONMENTAL FLOW METHODS
Methods to determine environmental water allocations (formerly termed ‘in-stream flows’, now generally called
‘environmental flows’ or ‘water regimes’ (to accommodate wetlands and groundwater systems) have been
explored in Australia since the 1980s (e.g. Richardson, 1986; Hall, 1989). Several texts, conference publications
and literature reviews (Gordon et al., 1992; Arthington and Pusey, 1993; AWWA, 1994; Tharme, 1996; Arthington
and Zalucki, 1998; Dunbar et al., 1998; Tharme, 2000, this issue) describe and compare individual methods used in
Australia to define the flows required for maintenance of geomorphological processes and channel morphology,
aquatic and riparian vegetation, invertebrates, freshwater fish, other river-dependent vertebrates, wetlands and
estuaries. Many of these methods are still in use. However, since 1992, several broader methodologies have been
developed to address the water requirements of the ‘riverine ecosystem’ (Arthington et al., 1992) rather than the
needs of just a few aquatic taxa (e.g. fish species of significance for recreational fishing and/or conservation, riparian and wetland vegetation, waterbirds). Arthington and Pusey (1993) describe Australia’s progression from ‘rules
of thumb’ to the present-day emphasis on the water requirements of ecosystems. Methodologies that consider the
entire riverine ecosystem include the holistic approach (Arthington et al., 1992; P. M. Davies et al., unpublished
report, 1996; Pettit et al., 2001), and the building block methodology (Arthington and Long, 1997; Arthington and
Lloyd, 1998; King and Louw, 1998), the expert panel method (Swales and Harris, 1995), the scientific panel
method (e.g. Thoms et al., 1996), the flow restoration methodology (Arthington et al., 2000), the benchmarking
methodology (Brizga, 2000) and DRIFT (downstream response to imposed flow transformation) (King et al., this
issue). Each of these methods is described in Arthington (1998) and/or Tharme (2000).
The ‘natural flows paradigm’ (Poff et al., 1997) and basic principles of river corridor restoration (Ward et al.,
2001) underpin all of these ecosystem methodologies (now termed ‘holistic’ methodologies by Tharme, 1996, this
issue). Their common objective is to maintain or partially restore important characteristics of the natural (or modelled unregulated) flow regime (i.e. the quantity, frequency, timing and duration of flow events, rates of change and
predictability/variability) required to maintain or restore the biophysical components and ecological processes of
in-stream and groundwater systems, floodplains and downstream receiving waters (e.g. terminal lakes and wetlands, or estuaries). Arthington et al. (1998) divided these methodologies into two main types: ‘bottom-up’, that
is, methods that ‘construct’ a modified flow regime by adding flow components to a baseline of zero flow (this
category includes the holistic approach and the South African building block methodology); and ‘top-down’ methodologies. The latter type addresses the question: How much can we modify a river’s flow regime before the aquatic ecosystem begins to noticeably change or becomes seriously degraded?
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Table I. National Principles for the Provision of Water for Ecosystems (ARMCANZ, ANZECC, 1996)
GOAL
The goal for providing water for the environment is to sustain and where necessary restore
ecological processes and biodiversity of water-dependent ecosystems.
PRINCIPLES
Basic premise of principles
Principle 1
River regulation and/or consumptive use should be recognised as potentially impacting on
ecological values.
Determining environmental water provisions
Principle 2
Provision of water for ecosystems should be on the basis of the best scientific information
available on the water regimes necessary to sustain the ecological values of water-dependent
ecosystems.
Provision of water for ecosystems
Principle 3
Environmental water provisions should be legally recognized.
Principle 4
In systems where there are existing users, provision of water for ecosystems should go as far
as possible to meet the water regime necessary to sustain the ecological values of aquatic
ecosystems whilst recognizing the existing rights of other water users.
Principle 5
Where environmental water requirements cannot be met due to existing uses, action (including
reallocation) should be taken to meet environmental needs.
Principle 6
Further allocation of water for any use should only be on the basis that natural ecological
processes and biodiversity are sustained (i.e. ecological values are sustained).
Management of environmental water allocations
Principle 7
Accountabilities in all aspects of management of environmental water provisions should be
transparent and clearly defined.
Principle 8
Environmental water provisions should be responsive to monitoring and improvements in
understanding of environmental water requirements.
Other uses
Principle 9
All water uses should be managed in a manner which recognizes ecological values.
Principle 10
Appropriate demand management and water pricing strategies should be used to assist in
sustaining ecological values of water resources.
Further research
Principle 11
Strategic and applied research to improve understanding of environmental water requirements
is essential.
Community involvement
Principle 12
All relevant environmental, social and economic stakeholders will be involved in water
allocation planning and decision-making on environmental water provisions.
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The benchmarking methodology (described in Arthington, 1998; Brizga, 2000) is the only top-down methodology applied in Australia for assessing the risk of environmental impacts due to water resource development. It is
used routinely in Queensland and is beginning to be used in Western Australia. This methodology is designed to
link information on alterations of natural flow regimes with the geomorphological and ecological consequences of
flow regime change, by evaluating the condition of a range of river reaches subject to various degrees of flow regulation and water resource development. The flow regime of the study river is described in terms of a set of key
flow indicators or statistics of geomorphological and/or ecological relevance (derived from theoretical, empirical
and conceptual models). A suite of ‘benchmark models’ is then developed, each model linking the percentage
change in a particular flow statistic from its natural (pre-regulation) value with the observed geomorphological
and ecological impacts of flow regulation. These models are used to develop a risk assessment framework that
guides the evaluation of the potential environmental impacts of future scenarios of water resource development
and management (Brizga, 2000). DRIFT (downstream response to imposed flow transformation) also embodies
a top-down approach enabling predictions of the ecological impacts of flow regime change (King et al., this issue).
In contrast, the flow restoration methodology combines a ‘bottom-up’ and ‘top-down’ approach (Arthington,
1998). It was designed to define more precisely how the flow regime of a regulated river could be changed to
achieve defined geomorphological and ecological objectives and an overall shift in the ecological characteristics
of the riverine ecosystem towards the natural (pre-regulation) state (Arthington et al., 2000). It has particular relevance to rivers regulated by large dams but could be applied to any river system regulated by infrastructure (e.g. by
inter-basin transfer, weirs or levee banks) and to situations of run-of-the-river water abstractions or alterations to
wetland water regimes and groundwater tables. One of its special features is that alternatives to flow restoration
(e.g. physical habitat restoration) are evaluated when some elements of the pre-regulation flow regime cannot be
restored fully for practical or legal reasons.
Within each of these holistic, ecosystem approaches, the particular methods, tools and models employed to
define the flow requirements of specific ecosystem components vary largely, it seems, as a function of the spatial
scale of the study and the time and resources available to undertake it. Such methods may include wetted perimeter
analysis, the physical habitat module of IFIM (the instream flow incremental methodology) (Bovee, 1982;
Milhouse et al., 1989), the flow events method describing the statistical properties of flow components judged
to be of geomorphological or ecological importance (Stewardson and Cottingham, 2002), wetland and riparian
water budget analysis (e.g. Pettit et al., 2001) and the characterization of flow pulses designed to mobilize sediments, maintain water quality and substrate composition, inundate channel benches, backwaters and floodplain
terraces, provide cues that initiate biological events (e.g. fish migration, spawning, flowring and seed set) and drive
ecological processes (energy flow, material exchanges between river channels, floodplains or the downstream
estuary; see Loneragan and Bunn, 1999). Although such methods (some involving modelling approaches) are
available, many environmental flow studies, short on time and resources, have been forced to rely heavily on
the theoretical literature, conceptual models and best professional judgement rather than undertaking new field
work or modelling activities. This is particularly the case for many applications of ‘expert’ and ‘scientific panel’
methods, which have become a way of fast-tracking environmental flow evaluations in many circumstances
(Cottingham et al., 2002).
Environmental flow studies based on a firmer foundation of knowledge (and predictive models) describing the
relationships between hydrology and ecological processes in particular rivers are relatively rare in Australia.
Applications of the holistic approach in Western Australia (P. M. Davies et al., unpublished report, 1996; Pettit
et al., 2001) and in Queensland rivers (for example, the Brisbane River (Arthington et al., 2000) and Logan/Albert
River (Arthington and Long, 1997; Arthington and Lloyd, 1998)) are exceptions, drawing on several years of field
data. These better grounded studies are rare for one major reason: the past limited commitment of funding agencies
to long-term ecological research on rivers and their floodplains in relation to the hydrological regime. Most river
research in Australia has been conducted within three-year (or even shorter) funding programmes. The Commonwealth’s ‘Environmental Flows Initiative’, an R&D programme established in 1999 with strong support from
scientists and government water managers, has lacked institutional commitment. Recently, Land and Water Australia (the former Land and Water Resources Research and Development Corporation) has resolved to fund environmental flows research (N. Schofield, personal communication, 2002), after a hiatus of some years, giving
renewed hope for a more consistent and supportive research programme.
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In data-poor settings, expert panel assessments continue to propose probability statements based on ‘rules of
thumb’. These serve their immediate purpose (i.e. setting some sort of ‘cap’ on further water diversions, or providing
interim targets for flow restoration). However, they may also serve to undermine the past decade of efforts to place
environmental flow assessments on a firm scientific foundation, based on understanding the ecological roles of the
natural flow regime and using this understanding to produce quantitative descriptions of restorative and protective
flow regimes. In over-committed river basins, such as the Murray–Darling, benchmarking could easily be applied,
based on the many regulated and degraded sections of this river, followed by application of the flow restoration methodology to define scientifically sound flow restoration targets and scenarios in key reaches and tributaries.
One of the features of water management for the environment is the insistence of different jurisdictions that
because all rivers are different, it is not possible simply to adopt environmental flow methods and guidelines from
other jurisdictions. Thus, a high number of different methods has been developed and used in Australia (37 in total;
Tharme, this issue). The general failure of most jurisdictions to learn from the experiences (successful or not) of
others typifies the overall water reform programme. In Australia, there has been only one national conference on
environmental flows with a published proceedings (AWWA, 1994) since the introduction of the water reforms, and
despite the wealth of published and grey literature freely available, and dozens of journal and conference papers,
we see much re-invention of the environmental ‘water wheel’. Thus, the state of Victoria is only now proposing its
definitive method (called FLOWS) for the estimation of environmental flows, even though the very first of such
studies was conducted in that state in the 1980s (e.g. Hall, 1989). In an effort to apply more quantitative methods in
Victoria, Stewardson and Cottingham (2002) have developed the flow events method. This provides a means of
quantifying the components of flow that ecologists recommend should be retained or restored for specific ecological purposes, with a particular emphasis on maintaining variability.
A final point regarding methods is that the techniques of risk assessment so well-developed and effectively
applied in relation to water quality management in Australia (National Water Quality Management Strategy) have
not been employed to any extent in environmental flow studies. This is surely a conundrum given the pivotal definition of ecological water requirements: ‘descriptions of the water regimes needed to sustain the ecological values
of water-dependent ecosystems at a low level of risk’ (ARMCANZ, ANZECC, 1996). The benchmarking methodology appears to be the only structured process to provide a risk assessment framework (based on the assessment
of river response to past flow regulation) within which future scenarios of water use can be evaluated in terms of
their probable impact on aquatic ecosystems.
A best practice framework (Arthington et al., 1998) proposed a logical sequence of activities leading up to, and
following, an environmental flow assessment, within which any of the methods or methodologies outlined above
could be applied. It includes a process of peer review and a monitoring and feedback loop intended to allow adjustments of environmental flows as new knowledge becomes available through monitoring and research. Some form
of peer review process seems necessary and important to ensure scientific rigour, credibility and confidence in
water allocation recommendations that may be very costly, practically and politically difficult to achieve, and
fraught with social and legal implications. Because doubts have been raised about the scientific foundations of
some environmental flow recommendations, scientists are now being pitted against consultants employed by
the proponents of new water resource developments, and litigation has already occurred to secure access to water
for irrigation purposes (e.g. in the Condamine–Balonne system of the upper Murray–Darling Basin). However, no
amount of challenge or litigation will solve the fundamental problem that ecological science cannot yet predict
how any stream or river, or any one component of it such as the fish assemblage, or even a single aquatic species,
will respond to alterations in the flow regime.
PROGRESS WITH FLOW PROTECTION AND RESTORATION IN AUSTRALIA
Flow protection
There is widespread agreement that it is far cheaper for society to prevent degradation of rivers and their floodplains in the first place than it is to restore degraded aquatic ecosystems. For example, the Snowy River Restoration
Project (see below) will cost at least $643 million to achieve total quantifiable benefits of only $61 million (Pigram,
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2000). Nevill (2001) has analysed the legislative and institutional background to biodiversity conservation in
Australia, and the nation’s progress towards the identification of important aquatic areas for conservation in protected reserves. Even the streams that flow through areas protected by national parks, fauna reserves and Ramsar
sites are not protected from all human disturbances. Streams in the Wet Tropics World Heritage Area of northern
Queensland are becoming enriched with nutrients emitted by tourists, water is being extracted for resort use and
translocated fish are treated as a major recreational resource rather than a threat to native biota. Not a single Australian river system is fully protected by the existing national reserve system, nor does the Ramsar Convention
afford protection to many of Australia’s most significant wetlands (McComb and Lake, 1990).
Nevill (2001; also P. Cullen, unpublished presentation, 2001) advocates setting up a National Heritage River
System, starting with rivers of high conservation value identified by the states and territories in their water allocation programmes, and/or already protected by conservation reserves. These rivers may include arid-zone rivers
(Georgina, Diamantina and Cooper Creek), rivers within the Wet Tropics World Heritage Area of Queensland,
the Lake Eyre Basin, the Clarence River in New South Wales, the Ovens River in Victoria, rivers within the World
Heritage Area of southwestern Tasmania, the Fitzroy River and Shannon River in Western Australia, and the East
Alligator River and others in the Northern Territory. Many wetlands recognized as priority areas for conservation
(Arthington and Hegerl, 1988; McComb and Lake, 1990), for example the Barmah–Millewa River Red Gum
Forest and other significant wetlands on the River Murray, groundwater wetlands in Western Australia and floodplain wetlands in Queensland, as well as many others, could be linked into a national network of aquatic reserves.
Quite apart from their heritage values, these rivers and wetlands will serve as the major sources of propagules and
colonists for degraded rivers and wetlands that have already lost much of their biological diversity.
Flow restoration
Restoration is defined by Middleton (1999) as ‘returning a site to a condition similar to the one that existed before
it was altered, along with its predisturbance functions and related physical, chemical and biological characteristics.
The goal of restoration is to establish a site that is self-regulating and integrated within its landscape, rather than to
re-establish an aboriginal condition . . . ’. Rehabilitation is a different process in that it seeks to improve the condition
of an area but not necessarily in the direction of the pre-existing undamaged state (Bradshaw, 1997).
Environmental flow determinations for Australian regulated rivers are consistent with Middleton’s definition of
restoration. They aim to identify and restore flow components that will move a river in the direction of its natural
condition, or the best representation of this that can be identified. Many river rehabilitation works have been undertaken in the past, and even today, some aspects of water and river management are more aligned with the goals of
rehabilitation sensu Bradshaw (1997). For instance, water management rules have been defined and experiments
conducted to achieve the suppression of algal blooms in weirs (e.g. Maier et al., 2001) with the prime objective of
preventing the outbreak of potentially toxic cyanobacterial blooms, rather than re-establishing natural communities of algae and periphyton. In southern rivers, flows and habitat have been managed in such a way that exotic
trout will continue to flourish and sustain recreational fishing.
The CoAG reforms require water allocations to ‘stressed rivers’, wetlands, floodplains, terminal lakes, estuaries
and ecosystems dependent primarily upon groundwater. The following provides a brief summary of progress and
notable examples of flow restoration studies.
Data from the National Land and Water Resources Audit (NL&WRA, 2000) suggest that 26% of rivers and a
similar proportion of groundwater systems are presently over-allocated, that is, they cannot sustain the current
levels of water use and still maintain ecological values. This is probably a very conservative figure as the methods
used to define and estimate ‘sustainable levels of water diversions’ (NL&WRA, 2000) have differed from one state
to another, and the amounts of water considered adequate to sustain river and groundwater ecosystems are poorly
documented in the Audit reports and remain for the most part obscure.
The Commonwealth National Competition Council has recently reported ‘significant progress with land and
water reforms’ which cost Australia $2.2 billion annually. All states and territories have introduced new water
legislation giving the environment formal, legal water rights, and progress reports suggest that over 50% of
Australia’s rivers, wetlands and groundwater systems have been evaluated and will receive some form of environmental water allocation.
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The rest of this section of the paper presents several case studies that illustrate the diversity of approaches being
used in Australia to restore river flow regimes and aquatic ecosystems, the amounts of water that may be involved
and the anticipated ecological outcomes.
Snowy River Restoration Project
The Snowy River rises in southeastern Australia and flows to the sea at Marlo on the Victorian coast. In 1974, the
Snowy Mountains Hydro-electric Scheme was completed at a cost of $800 million, and began to divert over
1 106 Ml of water annually (representing 99% of mean daily flow) from the upper catchment westward to the
Murray–Darling Basin. This inter-basin transfer scheme underwrites $1542 million worth of agricultural products
from the Murray and Murrumbidgee valleys (Davies et al., 1992; Pigram, 2000). With Jindabyne Dam in place,
large floods in excess of 40 000 Ml day1 continue to pass downstream with their frequency unaltered by dams and
diversions, but floods in the range of 20 000 Ml and 30 000 Ml day1 occur much less frequently than in the freeflowing river. Their loss has caused a range of geomorphological and ecological impacts exacerbated by changes in
catchment land-use. The channel below Jindabyne Dam has become narrow, increasingly vegetated, silted up and
less diverse, physically and biologically (Pigram, 2000). Using an expert panel approach and reviews of existing
ecological data, scientists have recommended 28% of mean annual flow below Jindabyne as the overall target for
restoration of the Snowy’s flow regime. Details of the seasonal distribution of flows, and the volume and duration
of particular flow events, are still being decided, but the general principle is to apply a holistic approach and mimic
important features of the pre-regulation flow regime. Environmental flows are expected to achieve improvements
in thermal regime, channel structure, longitudinal connectivity, dispersal and migration of biota, triggers for fish
spawning and the aesthetics of the degraded riverine environment. A monitoring programme has been put in place
to ‘benchmark’ the existing condition of the river before the flows are restored and to track the anticipated ecological outcomes.
The Murray–Darling Basin and the cap on water diversions
The Murray–Darling Basin spreads over an area of 1.073 106 km2 or about 14% of the total area of Australia,
and across parts of four Australian states (New South Wales, Victoria, Queensland and South Australia) and all of
the Australian Capital Territory. These governments and the Federal Government share responsibility for managing the natural resources of the basin. Some form of inter-state cooperation in the management of the basin’s
water resources has been in place since 1902, and from 1985, the Murray–Darling Basin Commission (MDBC)
has facilitated institutional arrangements (Close and McLeod, 2000). The aquatic ecosystems of the Murray–
Darling Basin have been more affected by flow regulation and water diversions than any other Australian catchment (Kingsford, 2000). Impoundments can store 103% of the mean annual runoff and 81% of total divertible
water is extracted, primarily for irrigated agriculture. The mean annual flow at the Murray mouth is only 39%
of natural.
The very first environmental flow provision in the basin was an allocation of 100 Gl year1 for watering the
Barmah–Millewa Forest (65 000 ha) on the River Murray. This forest is the largest contiguous stand of river red
gum (Eucalyptus camaldulensis) in the world and is listed under the Ramsar Convention. About 54 waterbird species breed in the forest and a further ten species are non-breeding vagrants or migrants listed in Japan Australia
Migratory Birds Agreement (JAMBA) and the China Australia Migratory Birds Agreement (CAMBA). Natural
flooding creates suitable nest sites and foraging areas and the fecundity of colonially nesting waterbirds is contingent upon the timing, magnitude, duration and frequency of flooding, and the rate of water level recession
(Leslie, 2001). By reducing the number and duration of floods, river regulation has reduced the frequency of successful breeding episodes by more than 80% compared to the natural precedent (Leslie, 2001). The first environmental flow of 100 Gl to the forest in 1998 achieved negligible ecological benefit, and modelling studies have
subsequently shown that accumulating this environmental flow provision for a number of years, to allow a larger
periodic release, would achieve better environmental outcomes than releasing 100 Gl each year (NRE, 1999).
Environmental water releases have now been tailored to satisfy the known water requirements of a range of wetland biota, especially the breeding of waterbirds. In 2000–2001, the first effective natural flood since 1993 was
enhanced by the largest environmental water release yet made in Australia (a total of 341 Gl, released in three
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parcels of water). This carefully crafted environmental flow strategy enabled at least 15 000 breeding pairs of 20 or
more waterbird species to breed successfully in the forest, and one endangered egret species bred for the first time
since 1975 (Leslie and Ward, 2002).
While the river red gum forests at Barmah may be reasonably well-watered in some years, others further down
the Murray River such as the wetlands at Chowilla have been deprived of their natural flood flows, and many other
parts of this river system have been adversely affected by flow regulation (Kingsford, 2000). In 1995, following an
extensive audit of water use, the Murray–Darling Ministerial Council introduced a basin-wide cap on further water
diversions. This ‘cap’ is intended to limit the volume of water diversions to 1993/1994 levels of development. New
developments are possible under the cap provided that the water for them is obtained by improving water use efficiency or by purchasing water from existing developments (Close and McLeod, 2000). The cap has been hailed as
a major innovation in water management with few international precedents. However, ecologists warn that while
the cap is an essential step in slowing ecosystem decline, it cannot be expected to result in marked improvements in
riverine health because it has been set at a level of water extraction that contributed to the current degradation of
the river system, (Whittington et al., 2000).
A recent review of environmental flow allocations for the River Murray calculated that a 40% reduction in the
existing cap, or 4000 Gl more water basin-wide, would be needed to restore critical flow volumes and flood pulses
of ecologically relevant size and frequency, and significantly improve the ecological condition of the river system
(G. Jones et al., unpublished report, 2001). This project used a risk-based approach to evaluate various scenarios of
ecosystem recovery, proposing that a regulated river will tend to shift towards a healthy condition if various important flow ‘indicators’ (hydrological statistics) can be restored to two-thirds of their pre-regulation level. The ‘twothirds natural’ level was intended as a possible target for restoration of the ‘working’ (i.e. regulated) River Murray,
not a level for ‘acceptable degradation’ or ‘sustainable diversion’ of minimally impacted rivers. It has since been
reformulated as the two-thirds rule, expressed as follows (Cullen, 2001): ‘Any river where more than 1/3 of the
median flow is extracted is likely to be seriously damaged. In such catchments, there should be an annual clawback of water for the environment until this level is reached or, a sustainable level of extraction is determined
through sound research. Compensation should only be paid where there is a genuine legal right to this water’.
Cullen’s rule refers to only median annual flow; however, G. Jones et al. (unpublished report, 2001) applied the
two-thirds criterion to a range of flow statistics describing important characteristics of the flow regime (magnitude,
timing, frequency, duration and rate of rise and fall of flood pulses, seasonal flow patterns, and flow variability)
with known or presumed relevance to river ecosystem components. So the proposed two-thirds rule is less of a
blunt instrument than might appear.
In northern valleys of New South Wales where irrigated cotton is the major crop, environmental water allocations have reduced diversions in the Gwydir Valley to 11% below cap ¼ 37 000 Ml year1 and in the Macquarie
Valley to 12% below cap ¼ 54 000 Ml year1. These reductions in water diversions are restoring about 10% of river
water on average to the valleys of the upper Murray–Darling system. Despite the small amount of water involved,
environmental flow management targets have been established, based around 12 broad River Flow Objectives
(Chessman and Jones, 2001). These objectives range from protecting low channel flows and pool water levels
and mimicking the natural frequency, duration and seasonal nature of drying periods in temporary streams, to
maintaining or restoring the natural inundation patterns and distribution of floodwaters supporting natural wetland
and floodplain ecosystems. As well as aiming to mimic natural patterns of river flow in the low-flow range, reservoir water is sometimes stored to create a ‘bank’ of water that can be used for specific environmental purposes,
variously referred to as an ‘environmental contingency allowance’ or a ‘wildlife allocation’ (Chessman and Jones,
2001). The former bank ‘credits’ have been used to flush blooms of cyanobacteria, the latter to sustain waterfowl
breeding events. This type of release may mimic a natural flow event, or be used more as an intervention in the
natural pattern of river flows to achieve what is seen to be a worthwhile environmental goal.
Benchmarking flow regulation impacts
In Queensland, environmental flow determinations currently apply the benchmarking methodology (Brizga,
2000) to develop a risk assessment framework for the evaluation of future water infrastructure proposals in each
catchment. Benchmarking in the Burnett Basin has produced two risk levels, the first defining ‘the benchmarked
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level above which assessed sites are more likely to have undergone no/minor change from reference condition due
to water resource development’ and the second defining ‘the benchmarked level below which assessed sites are
more likely to have major/very major change from reference condition due to water resource development for at
least one ecosystem component’ (Brizga, 2000). A key point about the risk levels established for Queensland river
systems is the inference that a substantial proportion of the natural flow (about 80–90% of mean annual flow) may
need to be retained, without any change in seasonal patterns of flow, in order to maintain ecological values at a low
level of risk. The principle that water flowing to the sea is not ‘wasted’ has also been established by demonstrating
strong correlations between the magnitude of summer discharge from coastal rivers and commercial fish and crab/
prawn catches in the Logan estuary (Loneragan and Bunn, 1999). The freshwater flow requirements of estuaries
are now considered on a routine basis as part of water resource plans in coastal catchments, and the techniques
developed in Queensland are also being applied in Western Australia.
Brisbane River flow restoration study
The flow restoration methodology (Arthington et al., 2000) was developed to advise on the environmental flow
requirements of the Brisbane River downstream from Wivenhoe Dam. This storage was constructed primarily to
impound flood waters. The dam also provides the major source of potable water to Brisbane city by delivering a
steady flow of water (averaging 650 Ml day1) to a treatment station at Mt Crosby, and a small amount of electricity is generated at Splityard Creek Hydropower Station fed by water from Lake Wivenhoe.
The study, described in Arthington et al. (2000), required evaluation not only of environmental flow options, but
also a review of the operations of all water release rules, particularly those pertaining to flood management (governed by an Act of Parliament), and advice on restoring an inefficient fish ladder at Mt Crosby, as well as an assessment of the potential environmental impacts of electricity generation using the daily flow releases from Lake
Wivenhoe. This study demonstrated how the operation of Lake Wivenhoe as a ‘translucent dam’ (i.e. allowing some
flows to pass through as and when they occur) could restore not only ecologically important flow magnitudes but
also flood pulses and flow variability at various temporal scales (daily, flood events, monthly, and from year to year).
Hydrological simulations showed clearly which particular environmental flows could and could not be achieved
with the dam operating as a flood mitigation storage and major source of water for Brisbane. Modified dam operating rules, piped water delivery to Mt Crosby, physical channel rehabilitation to replace riffle habitats drowned out by
elevated low flows, reconstruction of the fish ladder, and tapping into alternative sources of water for Brisbane, were
all explored as part of the project’s recommendations, as were the implications for environment flows of future
growth in Brisbane’s urban and rural populations. The Brisbane River study demonstrates rapid progress from simplistic rule-of-thumb guidelines based on hydrological indicators (dismissed in the 1980s by Richardson (1986) and
by Arthington and Pusey (1993)) and expert panel approaches involving desktop studies and observation of water
releases from dams (admittedly intended to be the start of a more holistic process; Swales and Harris, 1995).
Flow restoration studies in Western Australia
The holistic approach (Arthington et al., 1992) is being used in Western Australia in flow restoration studies.
These identify the important geomorphological and ecological features of aquatic and riparian systems that are
dependent upon flow and/or groundwater, and from an understanding of flow–ecology relationships, specific ecological water requirements are defined for in-stream and riparian systems (P. M. Davies et al., unpublished report,
1996; Pettit et al., 2001). Particular issues for Western Australia are groundwater systems and wetlands (Froend
and McComb, 1994) and mitigating the downstream ecological effects of water-supply impoundments located on
the Darling Scarp. Permanent streams originating on the scarp have very high quality water and contain ancient
Gondwanic fauna. Their lower reaches flow across the Swan Coastal Plain, where one of the major allocation
issues is maintaining flow permanence and ensuring water quality in pools, particularly dissolved oxygen concentrations over the dry summer months, and thus the capacity of pools to provide summer refugia for fish and invertebrates (P. M. Davies et al., unpublished report, 1996). Modelling techniques are being used to predict dissolved
oxygen concentrations in pools based on pool volume, in-flow and out-flow, rates of gross primary production and
respiration, day length and water temperature (P. M. Davies et al., unpublished report, 1996; P. Davies, University
of Western Australia, personal communication 2002).
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HOW MUCH WATER DOES A RIVER NEED?
Rivers and their floodplains need their natural flow regime in all of its spatial and temporal variability to maintain
their natural ecological integrity and long-term evolutionary potential (see reviews in Arthington et al., 1992;
Lake, 1995; Walker et al., 1995; Poff et al., 1997; Richter et al., 1997; Puckridge et al., 1998; Ward et al.,
2001; Bunn and Arthington, 2002). A water regime that is near to the natural unregulated state is the target for
National Heritage Rivers, Ramsar wetlands and aquatic systems in World Heritage Areas and national parks. Such
a target is not impossible, although it will involve some flow restoration activities, and other drivers of ecological
processes in rivers and their floodplains (i.e. catchment and riparian vegetation, sediment regime and water quality)
must also be kept intact to achieve long-term protection of these systems.
In an ideal world, environmental water requirements would be defined, and alternative water resource developments or restoration scenarios evaluated, by means of quantitative predictive models of the relationships between
hydrology and the ecological processes governing biological diversity and ecosystem integrity. Such models are
not yet available for any Australian river system and many of the available modelling techniques are prohibitively
expensive, particularly at a ‘whole-of-catchment’ scale. Scientists can certainly demonstrate from research in unregulated rivers that some fish species spawn during periods of low and relatively stable spring–summer flows (e.g.
Milton and Arthington, 1984; Humphries and Lake, 2000; Pusey et al., 2001) whilst for others spawning is triggered by flow pulses, and that waterbird breeding and recruitment in floodplain wetlands are dependent upon the
timing, duration and frequency of floods (Leslie, 2001). However, water managers need to know how far these flow
attributes can be altered from their natural levels before fish fail to spawn, or recruitment of waterbirds falls off
drastically. Likewise, those with the responsibility for river management need to be convinced that restoring 10%
or 20% of flow magnitude, or five small floods instead of one larger one, will have measurable ecological benefit
(Bunn and Arthington, 2002).
The benchmarking methodology applied in Queensland water resource planning appears to offer the most tractable method for making probability statements about the ecological implications of altering a river’s flow regime by
specified amounts compared to the natural regime. While the risk assessment models of the benchmarking methodology are superficially similar to the outputs of rule-of-thumb methods such as the Montana method (Tennant,
1976) (i.e. ecologically significant levels of change are related to a set of key flow indicators) there are substantial
differences in how the outputs are derived. In particular, benchmarking provides a framework which enables locally
applicable models of river condition versus hydrological change to be developed. It also provides a structured
approach for incorporating scientific understanding of the complex role of flow in ecosystems that goes well beyond
the simple relationships originally recognized by the Montana method. However, until we have a better understanding of how flow–ecology relationships may vary across the individual subcatchments of large river basins with distinctly different flow regimes (see Pusey and Arthington, 1996; Pusey et al., 1998), from basin to basin and between
biogeographic regions (e.g. Pusey et al., 2000), the benchmarking methodology must be applied with caution. It
should be used only as a ‘holding position’ whilst research and monitoring strengthen our understanding of how
rivers have in the past, and will in the future, respond to change in their individualistic flow regimes.
In the interim, something must be done, and done quickly, to prevent further deterioration of river condition in
most areas of Australia, especially in areas dominanted by irrigated agriculture. The studies conducted to date in
Queensland rivers suggest that at least 80–90% of natural flows (as measured by a core set of hydrological
indicators) may be needed to maintain a low risk of environmental degradation, based on the Fitzroy, Barron
and Burnett River benchmarking studies. In the Top End of the Northern Territory, some rivers are maintained at
80% of their natural flow, whereas in the case studies reviewed above, two-thirds of various flow indicators has been
proposed as the restoration target for the River Murray, and a value of only 28% of natural mean annual flow has
been negotiated for the Snowy River. It may well be that some rivers can maintain their fundamental ecological
integrity with less than 80–90% of natural flows, but this has yet to be demonstrated. Advocating only 66% of a
series of flow statistics for a regulated river with significant water infrastructure may help the River Murray to
recover some of its natural values, but must not be interpreted as a national ‘target flow’ that could pre-empt more
systematic analyses of environmental flow requirements and more generous flow allocations. Furthermore, it must
not detract from options for achieving different levels of restoration in various tributaries and reaches of large rivers,
and certainly should not be used as a level for sustainable diversion of minimally impacted rivers.
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We propose as an immediate alternative to the two-thirds rule: that river-specific benchmark models be developed throughout Australia using well-established quantitative field techniques for the assessment of river condition, and further, that the risk assessments made possible using benchmarking should be used to ‘cap’ further water
diversions until more robust estimates of flow requirements can be determined through research. We made a similar recommendation to cap water diversions ten years ago (Arthington and Pusey, 1993). If a national benchmarking programme is put in place, it will be essential for scientists to communicate the message that benchmark levels
must be treated as hypotheses rather than as fixed targets for flow restoration and protection. Furthermore, ecologists must be given opportunities to test these hypotheses through short- and long-term experimental research and
monitoring, and given the time, funding and institutional support to do so.
Flow restoration experiments
Conceptual models describing the processes underlying anticipated restoration trajectories abound in the literature
and reports from environmental flow studies, giving wide scope for hypothesis-driven flow restoration research and
monitoring as an explicit component of flow restoration projects. Although there are significant experimental design
issues (few suitable reference systems and limited opportunities for replication), turning flow restoration projects into
experiments in restoration ecology is long overdue (Kingsford, 2000; Lake, 2001; Bunn and Arthington, 2002).
We recommend the establishment of a series of demonstration flow restoration projects in focus catchments
around Australia with significant problems due to flow regulation and realistic opportunities for flow restoration.
Each case study could be planned and managed according to a standard format for monitoring and assessment of
critical variables related to flow and flow-driven ecological processes. The monitoring and assessment programme
should be designed to determine the outcomes of particular changes in key flow characteristics (described by key
flow statistics) representing the major types of changes being made in flow regimes in different areas of Australia.
The opportunity to build hypothesis testing into flow restoration projects has been taken up in some jurisdictions. The New South Wales IMEF (Integrated Monitoring of Environmental Flows) programme has been designed
to link four components: a flow rule or rules; the River Flow Objective (RFO) that the flow rule is designed to
achieve; an intended environmental outcome of the RFO; and the biophysical mechanism by which the application
of the rule is expected to lead to the outcome. As the authors of IMEF state: ‘Hypothesis testing would enable the
expected links between the flow regimes and ecology to be either confirmed or reformulated, regardless of whether
or not a long-term ecological improvement is recorded’ (Chessman and Jones, 2001).
The Co-operative Research Centre (CRC) for Freshwater Ecology is conducting a long-term flow restoration
project in the Campaspe River, where the effects of operating Lake Eppalock as a ‘translucent’ dam (allowing
some of the in-flow to the dam to be released downstream as and when it arrives) are being monitored. At present
minimal releases are made from the lake outside of the summer irrigation season. The proposed new flow regime
will allow 25% of Lake Eppalock’s incoming water to be released between May and October. The objective of the
experiment is to restore some of the natural seasonality and variability that existed before the river was impounded
and regulated, and by doing so, promote recovery of invertebrate and fish populations (Humphries et al., 1999;
Humphries and Lake, 2000). The new flow regime would not compromise existing users’ security of supply
because Lake Eppalock has to reach 64% capacity before any environmental water releases are made.
Long-term studies of flow restoration (such as the Campaspe Project) can be disrupted by natural variations of
rainfall and runoff, and other external influences. To date, the planned experimental flow release from Lake Eppalock has not been made because of water shortages in the catchment. Short-term and small-scale experimental water
releases, such as flows designed to trigger fish migration and spawning, offer a more tractable research alternative,
even though the range of issues that can be investigated in this way is limited. King et al. (1998) demonstrated that
experimental releases from the Clanwilliam Dam on the Olifants River, South Africa, resulted in spawning of the
Clanwilliam yellowfish, but suitable water temperatures were also required to ensure egg survival and larval development. Very little manipulative research of this type has been conducted in Australia’s regulated rivers.
Long-term ecological research
Commitment to restoration experiments has been difficult to achieve in Australia and this remains one of
two large gaps in river research. The second major gap is long-term research (Franklin, 1989) on flow-related
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ecological processes in rivers that have not been regulated or modified by major catchment disturbances. Research
in these systems is essential to provide a baseline understanding of river ecosystem functioning in relation to flow
regime, flow history and flow events, and predictive models of flow regulation impacts (Kingsford, 2000; Bunn and
Arthington, 2002). Such research is also needed to be able to predict restoration trajectories (Petts, 1987; Lake,
2001; Ward et al., 2001), and to predict the impacts of climate change on river ecosystems as their flow regimes
change in response to rising temperature, altered rainfall distributions, increasing evaporation rates and greater
water stress. Competing for environmental water allocations will be all the more difficult under future climatic
and hydrological scenarios, and aquatic ecologists are not well-equipped scientifically to deal with these added
pressures, nor have Australians in general faced up to the ‘adaptation challenge’ (Whetton, 2001) that increased
climate variability will present.
Saving water for environmental protection
How can we ‘claw back’ water for rivers? Cities use 8–10% of Australia’s stored water and up to 80% of such
water is used for watering lawns and gardens (Smith, 1998). Most cities have implemented water metering systems
and water pricing, and there is a significant and growing shift towards economical native plant gardens and ground
covers rather than the European style of brilliant green, over-fertilized and over-watered lawns (Smith, 1998).
However the efficiency gains so produced are likely to be absorbed by future population increases, and the drift
of urban settlements onto former agricultural holdings. City dwellers are well-disposed to environmental protection measures and many cities and towns exact some form of environmental levy as part of their land ratings. However, saving water in urban areas is only a minor part of the solution to Australia’s water crisis.
The agriculture sector uses 79% of stored water. Must this extravagant level of water use continue? Recent
research indicates that about 75% of Australia’s agricultural production comes from 25% of farms, representing
those that are profitable in the longer term, largely, but not only, because they have access to ample water for irrigation, whereas 25% of farms are marginal in terms of profits and 50% are not viable. Under the CoAG water
reforms one might expect that water allocations should be provided only to ecologically sustainable agricultural
systems. This may be the trend of the future under the reforms and more enlightened community, economic and
political agendas. However, many of the most profitable agricultural systems, for example cotton and sugar, have
devastating effects on the aquatic and surrounding riparian/terrestrial environment, manifest in the ‘irrigation syndrome’ and clearly evident in the cotton-growing areas of the Murray–Darling Basin (Arthington, 1996) and
around sugar cane plantations in the Burnett catchment and further north (Arthington et al., 1997). If fully implemented and regulated by governments, ecologically sustainable agricultural practices could result in significant
savings of water to be restored for environmental purposes. However the battles over water now taking place in
such catchments as the Condamine–Balonne and the Burnett suggest that sustainable agricultural systems may be a
long while off.
The CoAG reforms also provide the principles and the platform for implementing full-cost pricing of water to
provide an incentive for efficiencies in water use across all sectors, but particularly in the agricultural sector, where
levels of wastage are known to be very high (Postel, 2000). Water savings achieved under government-funded
water use efficiency programmes should be returned to the environment, and a percentage of the water acquired
via water trading could also be returned.
Environmental water banks and water trading
The above mechanisms for retrieval of water for rivers and wetlands are likely to take a long time to achieve in
Australia, and whilst the various institutional, economic, social and political adjustments are taking place, rivers
will continue to degrade. Many rivers, especially those in rural areas, need immediate attention. How can more
water for the environment be acquired now? We can see no alternative but for the environment to be a participant in
the water market. It would seem fanciful to suggest that, just as farmers are compensated for loss of property, crops
and income due to disastrous floods and droughts, the environment, now a legal ‘user’ of water in Australia, should
be compensated for its past water losses to off-stream use. However, we suggest the establishment of ‘water banks’,
not reservoirs full of water to be used only for environmental purposes (although shares in reservoir water volumes
will play a part in providing more water for the environment), but financial banks, operated by ‘river managers’
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with the power and legal right to buy and sell water on behalf of the environment. To resource these water banks,
penalties for failure to meet environmental flow targets would be paid to the river managers. Several potential
mechanisms to raise funds for the water banks are already well-established in other areas of natural resource management and conservation. As a nation, we could establish a system giving citizens the option to make voluntary
contributions on each water bill to fund water banks in rural and other critical areas. Finally, raising large national
and international donations to water banks is a very real option, that is already taking effect through the activities of
organizations such as World Wildlife and the American Nature Conservation Agency. Backed by such arrangements and adequate start-up funding, environmental water trading could be a viable future scenario for water management in Australia.
ACKNOWLEDGEMENTS
We thank Dr Jackie King from the University of Cape Town, South Africa, for inviting this paper and her many
forms of support and encouragement over the past decade. This paper represents a contribution from the Cooperative Research Centre for Freshwater Ecology and the Co-operative Research for Rainforest Ecology and
Management, and we thank both centres for funding support. We also acknowledge in-kind and intellectual contributions from Griffith University and our colleagues there, in particular Professor Stuart Bunn, Mark Kennard,
Steve Mackay, Steve and Fiona Balcombe, Fran Sheldon, Glen Wilson, Christopher Irons, Maria Barrett and Lacey
Shaw. Thanks are due to Sue Capon for drawing Figure 1. Finally, we are grateful to our many colleagues from
other institutions who responded to an informal survey. Many will recognize their contribution in the preceding
text.
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