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CRC for Freshwater Ecology ACT e-flow guidelines review

Review of the 1999 ACT Environmental Flow Guidelines

A report by the CRCFE to Environment ACT

November 2004

By:Ralph OgdenPeter DaviesBronwyn RennieJames MugodoPeter Cottingham

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This report has been prepared by: Ralph Ogden1, Peter Davies2, Bronwyn Rennie1, James Mugodo1, and Peter

Cottingham1.

1. CRC for Freshwater Ecology

2. Freshwater Systems

AcknowledgmentsThis report is based on a review conducted by the CRC for Freshwater Ecology and

Freshwater Systems as part of a consultancy for Environment ACT. A one-day

workshop was held by the CRCFE to support the review. We would like to thank and

acknowledge all workshop participants for their contributions:

Peter Liston (Environment ACT)

Heath Chester (Environment ACT)

Lucy Wildman (Environment ACT)

Mark Lintermanns (Environment ACT)

Nicole Davis (ACTEW)

Kirilly Dickson (ACTEW)

Gary Bickford (ACTEW)

Norm Mueller (Ecowise)

Peter Cottingham (CRCFE)

Claire Sellens (CRCFE)

Richard Norris (CRCFE)

We would also like to acknowledge the reviewers of this report:

Angela Arthington (Griffith University)

Gary Jones (CEO, CRC for Freshwater Ecology)

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The Cooperative Research Centre for Freshwater Ecology is a national research centre

specialising in river and wetland ecology. The CRC for Freshwater Ecology provides

ecological knowledge to help manage rivers for sustainability. The CRC was

established in 1993 under the Australian Government’s Cooperative Research Centre

Programme and is a joint venture between:

ACTEW Corporation

CSIRO Land and Water

Department of Environment and Conservation, NSW

Department of Infrastructure, Planning and Natural Resources, NSW

Department of Natural Resources and Mines, Queensland

Department of Sustainability and Environment, Victoria

Department of Water, Land and Biodiversity Conservation, South Australia

Environment ACT

Environment Protection Authority, Victoria

Goulburn-Murray Rural Water Authority

Griffith University

La Trobe University

Lower Murray Urban and Rural Water Authority

Melbourne Water

Monash University

Murray-Darling Basin Commission

Sydney Catchment Authority

University of Adelaide

University of Canberra

© Cooperative Research Centre for Freshwater Ecology

Tel: 02 6201 5168

Fax: 02 6201 5038

Email: [email protected]

Web: http://freshwater.canberra.edu.au

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A review of the ACT Environmental Flows Guidelines (1999)

Executive summary............................................................................................................21. Review...........................................................................................................................4

1.1 Scope...................................................................................................................41.2 Approach.............................................................................................................6

2. The 1999 Guidelines and related documents.................................................................72.1 Origin of environmental values, objectives and e-flow policies.........................72.2 The 1999 Environmental Flow Guidelines.........................................................8

3. New knowledge............................................................................................................123.1 Monitoring activities.........................................................................................123.2 R&D activities...................................................................................................133.3 Main messages for e-flow management............................................................15

4. Advice on appropriate approaches...............................................................................164.1 Context for e-flow management........................................................................164.2 Context of this review.......................................................................................164.3 Use of Ecological Objectives............................................................................164.4 Linking objectives to the flow regime...............................................................174.5 Monitoring & adaptive management.................................................................174.6 Linking e-flows restorations to refuge habitats.................................................18

5. Existing flow extraction and e-flow components........................................................205.1 Low flows..........................................................................................................205.2 Flushing flows...................................................................................................215.3 Flows in drought................................................................................................235.4 Special purpose flows........................................................................................235.5 Maximum diversion limits................................................................................245.6 Groundwater extraction.....................................................................................265.7 Drawdowns in urban lakes................................................................................265.8 Responses to fire...............................................................................................26

6. Potential new objectives and e-flows...........................................................................286.1 Draft values & objectives identified at workshop.............................................286.2 Science underpinning draft objectives..............................................................326.3 Other potential objectives..................................................................................346.4. Flow regime needed to satisfy objectives........................................................35

7. Advice on monitoring & adaptive management..........................................................367.1 Monitoring program..........................................................................................367.2 Adaptive management.......................................................................................38

8. References....................................................................................................................40Appendix A. Terms of Reference for review...................................................................44Appendix B. AUSRIVAS bands & their interpretation...................................................46

Division of O/E taxa into bands or categories for reporting...................................46Appendix C. Leaf-green Tree Frog (Cotter River Form).................................................47Appendix D. MLLE - Applying MLLE to Cotter River environmental flows................48

Introduction.............................................................................................................481) Characteristics of human activity........................................................................492) Characteristics of impact location.......................................................................493) Question(s) & Conceptual model........................................................................504) Relevant lines of evidence..................................................................................515) Collecting the evidence.......................................................................................516) Additional lines of evidence...............................................................................517) Weight all literature and local data relative to quality........................................51

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Executive summary

Background1) This is an ecological review of the ‘ACT Government Environmental Flow

Guidelines’ (1999) (or EFG). The EFG are a statutory document that establishes the water requirements in streams and lakes in the ACT, to ensure aquatic ecosystems are sustained. The CRC for Freshwater Ecology has been asked to provide advice on the efficacy of the EFG, and on improvements that can be made in the general approaches and actual flow rules for sustaining ecological values.

2) The approach taken in the review is to assess the effectiveness of prescribed environmental flows by reference to monitoring data and research on rivers within the ACT, and by consulting with local scientific experts. Advice is provided on the retention of current flow practices, or their modification to better achieve ecological objectives. This information could contribute to adaptive management in the near term, or to a more systematic formulation of environmental flow guidelines, should that be undertaken in the future.

Performance of the environmental flow guidelines3) The performance of environmental flows needs to be considered in reference

to objectives that reflect catchment uses as well as river condition. The approach taken in this review is to judge sustainability in reference to established ‘performance criteria’ where they exist.

4) In regulated parts of the Cotter River system the current EFG low-flow levels (supplemented by unmanaged reservoir spills and inflows), are delivering many desirable ecological benefits. General river condition is at or above levels specified in performance criteria, and appears to have improved since the implementation of the EFG, despite the drought and fires. Both Macquarie Perch and Two-spined Blackfish have successfully spawned during the drought.

5) Adaptive management principles embedded in the EFG, and further developed in practice, worked well in the Cotter River during 2003/04 in relation to setting environmental flows during drought and under a demonstrated needs scenario, as well as in relation to capturing new information.

6) In the Queanbeyan River downstream of Googong Dam the current EFG are maintaining conditions at or above performance criteria levels.

7) The monitoring data are insufficient to determine the ecological value of environmental flows in other systems.

Advice on retention of or changes to guidelines 8) A process of setting clear ecological objectives could be considered for all

river types and reaches within the managed area. The process could target

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systems with tailored environmental flows, and could involve focused monitoring to allow assessment of performance against the objectives.

9) This review provides draft ecological objectives, arising from a workshop held as part of the review. The review also proposes environmental flows that should achieve the objectives, or that can be be trialled.

10) Some suggestions are made for changes to existing environmental flows, including introducing flow variability in releases from the dams, major refinements to flushing flows, and a reduction in the flow required for fish spawning in the Cotter River.

11) Continued integration of environmental flow management, monitoring and assessment, within an adaptive management framework, will lead to ongoing benefits. Consideration should be given to having clearer formalisation of an active adaptive management strategy in the EFG.

12) Monitoring of the effectiveness of environmental flows to areas beyond the water supply reaches should be considered.

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1. Review

1.1 ScopeA review of the ecological benefits arising from application of the 'ACT Government Environmental Flow Guidelines' (ACT Government 1999c) has been conducted for Environment ACT, by the CRC for Freshwater Ecology and Freshwater Systems.

The Environmental Flow Guidelines (or EFG) establishes the water requirements in streams and lakes in the ACT (Figure 1) necessary to ensure aquatic ecosystems are sustained. The EFG apply to all rivers and streams in the ACT, to the urban lakes and to groundwater. By agreement they also provide guidance on how to the waters of the Queanbeyan and Molonglo Rivers in New South Wales (Figure 1) should be managed to ensure environmental values.

This report provides advice on the flow regimes needed to sustain ecological values. In particular it describes:

evidence, collected in monitoring and research activities, relating to the environmental efficacy of environmental flow provisions applied since the implementation of the Guidelines;

appropriate approaches for determining the flows needed to sustain aquatic ecosystems in the ACT;

the actual flows needed to sustain aquatic ecosystems in the ACT, or a method for determining actual flows where the data to determine actual flows are absent. Environment ACT seeks advice on flows for two scenarios: flows that would ensure either a moderate degree or a high degree of confidence that ecological values of aquatic ecosystems are maintained.

a flow regime that should sustain basic aquatic ecosystem processes without irreversible damage;

the importance of baseflows for maintaining aquatic ecosystems in ACT streams, and the extent to which this flow component should be protected to maintain ecological values;

the need for the maximum drawdown component to protect ecological condition (particularly macrophyte beds) in urban lakes and ponds, and the form of any such requirement;

the monitoring necessary to assess if the required ecological outcomes associated with environmental flow releases are achieved;

opportunities for adaptive management of environmental flows; other ecological issues related to flow regimes.

The full terms of reference are in Appendix A.

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Figure 1. Streams, rivers and reservoirs of the ACT (within boundary), and Water Management Catchments under the Water Resources Act 1998. Map courtesy of Environment ACT.

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1.2 Approach

The review was conducted in four steps.1. Publications and data were collated and reviewed, to identify the resulting key

messages and new knowledge. The publications and data had been generated in monitoring and research and development activities relevant to the EFG, and in compliance reporting for environmental flows.

2. A workshop of local experts was held to:a. review the key messages and initiate the development of specific

ecological objectives for each aquatic ecosystem type and/or reach which e-flow management will aim to achieve.

b. identify the individual flow regime components required to achieve the objectives, and make general suggestions for improving the EFG.

3. A draft report of the review was completed. It included an assessment of the existing EFG, and identified parts of the guidelines where changes might be considered and the process for determining how the EFG might be changed.

4. The draft report was peer reviewed. A final draft was completed incorporating feedback from the peer review.

A number of in-depth, systematic methods exist for formulating environmental flow guidelines (Arthington and Zalucki 1998; Arthington 1998), but time did not permit the use of these. This review therefore assesses the performance of the EFG, and offers advice on alternative approaches or actual flows to be considered where it appears the EFG are over- or under-performing.

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2. The 1999 Guidelines and related documents

2.1 Origin of environmental values, objectives and e-flow policiesThe environmental values and objectives for ACT waters, and overarching policies for protection of those environmental values, are set out in Appendix 1 of the ACT’s Territory Plan. The Water Resources Act requires the development of ACT Environmental Flow Guidelines (ACT Government 1999c). The EFG are thus a statutory document, and along with the Water Resources Act must be consistent with the Territory Plan. The EFG are implemented by the Water Resources Management Plan, the most recent version of which is the Think Water Act Water strategy.

Environmental objectives for the EFG derive from objectives set out in Section 2.1 of Appendix 1 of the Territory Plan, including:

to ensure that the streamflow and quality of discharges from the catchment are consistent with the protection of environmental values of downstream waters;

and the Water Resources Act objectives (listed in the 1999 EFG), which include: ensuring the use and management of water resources sustain the physical,

economic and social wellbeing of the people of the Territory while protecting the ecosystems that depend on those resources; and

protection of waterways and aquifers from damage and, where possible, to reverse the damage that has already occurred.

The EFG target ‘prescribed environmental values’ which are listed in Schedule 1 of Appendix 1 of the Territory Plan as:

Aquatic habitat — mountain streams Aquatic habitat — lowland streams Aquatic habitat — urban lakes and ponds Aquatic habitat — urban wetlands Aquatic habitat — mountain reservoirs

Policies in the Territory Plan for protecting environmental values are summarized in the EFG as follows:

land use and management practice shall be cognisant of streamflow and water quality impacts downstream;

stream flow diversions shall be restricted to authorized diversions; and lake and reservoir releases shall be consistent with the protection of

downstream ecology and water uses.

In the ACT there are six threatened aquatic species (Macquarie Perch, Two-spined Blackfish, Silver Perch, Trout Cod, Murray River Crayfish and Corroboree Frog). In addition, Murray Cod are listed as vulnerable under the federal Environment Protection and Biodiversity Conservation ACT (1999). There are other species that appear to be rare or have a limited distribution, and are valued by scientists working in the region (e.g. Cotter River Frog). However, the management of these has not been explicitly addressed in the EFG. As well, the general condition of rivers, as reflected by macroinvertebrate assemblages, has been formulated as a management target in the Cotter River, as reflected in ACTEW licensing (Table 1), but not within the EFG.

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Table 1. Performance objectives, indicators and criteria. Source: Licence No. WU67Period Performance objectives Performance indicators & criteria

Short to medium term:

Restoration of habitat quality & area

Restoration of macro-invertebrate composition & diversity

a) Streamflow replicates pre-dam seasonality (Cotter & Queanbeyan) flow patterns.

b) Water quality at sites below dams within ‘pristine’ to ‘slightly to moderately modified’ range for both the Cotter & Queanbeyan Rivers (within 10 – 90%ile range or within ± 2 std deviations of mean).

c) Macroinvertebrate O/E ratios at sites some distance below dams within ‘equivalent to reference’ condition (Cotter) (O/E > 0.85).

d) Macroinvertebrate O/E ratios at sites just below dams within ‘slightly to moderately impaired’ condition (Cotter) (0.85 > O/E > 0.6).

e) Macroinvertebrate O/E ratios for all sites on Queanbeyan below Googong within ‘slightly to moderately’ impaired condition (0.85 > O/E > 0.6).

Medium term:

Restoration of habitat quality & area

f) Reduced uniformity (Cu) in channel sediments grading, reduction in vegetation encroachment, increased area of frequency duration curves & inundated channel area

Long term: Restoration of native fishEstablishment of recreational fishery

g) Stable or increasing Population size and evidence of successful spawning of threatened species within reach (Cotter)

h) Population and individual sizes of stocked fish within Queanbeyan below Googong.

2.2 The 1999 Environmental Flow GuidelinesThe EFG apply to all rivers and streams in the ACT, to the urban lakes and to groundwater insofar as they are necessary to maintain aquatic ecosystems, and to sections of the Queanbeyan and Mologlo Rivers in New South Wales. Their primary purpose is to set out a method for the calculation of environmental flows to be used as the basis of the Water Resource Management Plan for the ACT.

‘Environmental flows’ (called ‘e-flows’ in this report) are defined in the EFG as:the streamflow necessary to sustain habitats (including channel morphology and substrate), encourage spawning and the migration of fauna species to previously unpopulated habitats, enable the processes upon which succession and biodiversity depend, and maintain the desired nutrient structure within lakes, streams, wetlands and riparian areas. Environmental flows may comprise components from the full range of flow conditions which describe long term average flows, variability of flows including low flows and irregular flooding events.

This is a very broad definition of environmental flows, which does not differentiate between managed and unmanaged flows.

The EFG are based on a ‘holistic’ approach to defining an e-flow regime, with: a philosophy of maintaining the aquatic ecosystem as a whole, rather than a

specific component; explicit provision for maintaining variability in river flow including seasonal

variation and flood flow; and provision for incorporating information on flow requirements of particular

ecosystem components when it becomes available.

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The EFG identify four types of aquatic ecosystem: natural, modified, water supply and created ecosystems (Figure 2), with broad management goals (Table 2).

Table 2. Types of aquatic ecosystems and their location. Source: EFG.Type of Aquatic

EcosystemDescription Management goal Water bodies in this category

Natural ecosystems

Ecosystems that have persisted from a period prior to European settlement.

Primary goal: Maintain ecosystems in their pristine state, Secondary goal: recreation

Water bodies in Namadgi National Park, excepting the Cotter River catchment

Modified ecosystems

Ecosystems modified by catchment activities (land use change, discharges) or by changes to the flow regime.

Should meet a range of functions; recreation, conservation.

Rivers, lakes and streams outside Namadgi and the Canberra urban area including Molonglo (except Lake Burley Griffin) and Queanbeyan Rivers.

Water supply ecosystems

Ecosystems in catchments that provide the ACT water supply.

Primary goal: Provide water supply, Secondary goal: conservation.

Cotter River catchment.

Created ecosystems

Ecosystems in urban lakes, ponds and streams that have developed since urbanisation

Should meet a range of functions; recreation, conservation, irrigation.

All urban lakes and streams.

For environmental purposes, all systems except the water supply ecosystems (the Cotter) and water supply reaches within modified ecosystems (the Queanbeyan River below Googong Dam, and the Molonglo River below Captains Flat Dam) are managed through:

1. protection of low flows, where low flows are defined as the flow level that is exceeded 80% of the time (80% exceedence), calculated on periods of not more than a month, as well as abstraction rates that are always less than flow rates;

2. a maximum diversion limit of 10% of the flow volume above the 80% exceedence flow value;

3. flushing flows, defined as flood events with a 1 : 1.5–2.5 years annual recurrence interval. Flushing flows are maintained by limiting diversions of higher flows as described in (2).

4. other flow rules (see EFG), e.g. for lakes and ponds in modified and created ecosystems, the maximum drawdown is 0.2 m below spillway level.

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‘Created’ ecosystem

‘Water Supply’ reach

‘Natural’ ecosystem

Aquatic refuge: pools

Aquatic refuge: reservoir

Figure 2. Conceptual diagram of the ACT catchments, showing the several types of ecosystems and that need to be managed, and aquatic refuges.

‘Modified ecosystem’

‘Water Supply’ ecosystem

KEY

River

Lake

Dam


The Cotter (water supply) system is managed differently in three reaches, Cotter A, B, C:

Cotter A — unregulated streams above Corin Dam Cotter B — transmission zone between Corin and Bendora Dams, and Cotter C — below water offtake at either Bendora or Cotter dams (Cotter Dam

has not been used for water supply for around 30 years, but is intended to be used in the future).

For the Cotter A reach:5. no abstractions are allowed.

In the Cotter B & C reaches, flows are managed as follows:6. protection of low flows, defined as flows below the 80% exceedence flow for

reservoir inflows. Inflows below this discharge are to be released.7. In periods when criteria are met for a demonstrated need for more water to be

allocated to water supply, up to 50% of the inflow below the 80% exceedence flow can be abstracted, by agreement.

8. In droughts, lower flows may be implemented that modify the above rules. Drought is defined as occurring when in nine of the preceding 12 months, flows into Corin and Googong Dams were less than the median monthly inflows, and the amount of water in ACT water supply reservoirs is less than 50% of total capacity. Flows close to the 100% exceedence flow level (i.e. the minimum recorded flow) are allowed from Bendora Dam in extreme circumstances, to mimic natural conditions and provide water savings, but may not drop below the 100% exceedence flow level.

9. No diversion limits once environmental flow requirements are met.10. Flow release patterns should mimic natural, and water temperatures as close to

those of inflows, as much as possible. Below Corin Dam (Cotter B reach) only:

11. Spawning flows — flows to be kept at or above the 50% exceedence flow level (monthly flow) for the September to November period, and above the 80% exceedence flow for August and for December to March, every two out of five years.

Note that a requirement for flushing flows was not made in the EFG for Cotter B and C, but that some releases have been trialled in Cotter C as flushing flows.

Water supply reaches within modified ecosystems (the Queanbeyan River below Googong Dam, and the Molonglo River below Captains Flat Dam) are managed through the protection of low flows (as in point 6, above), with even lower flows allowed where there is a demonstrated need (as in point 7, above), culminating in arrangements for flows in drought (as in point 8, above). There are no diversion limits once these environmental flow requirements are met.

Both the demonstrated needs and the drought provisions of the EFG were triggered during the recent drought period. Minimum e-flows for the recent drought period were set at 20 ML/d for the Cotter River (reach C) and 2 ML/d for the Queanbeyan River below Googong Dam.

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3. New knowledge

3.1 Monitoring activitiesThe 1999 Guidelines require monitoring of compliance with e-flow provisions and also of their environmental outcomes, with the results of this monitoring to be a primary input to a performance review. Benthic macroinvertebrate and fish sampling has been conducted at selected sites in the Cotter catchment (the water supply ecosystem) and the Queanbeyan River downstream of Googong Dam (a water supply reach within the modified ecosystem), the former using the AUSRIVAS methodology. This has been accompanied by spot sampling of water quality at selected sites. No analyses have been made to evaluate the performance of the EFG flow regimes in natural and created ecosystems, or outside the Queanbeyan River in the modified ecosystem.

The AUSRIVAS sampling in the Cotter has been focused on assessing compliance with performance criteria for ACTEW, under the ACT Government licence for ACTEW’s operations (Ecowise 2001–2003). No analysis has been conducted of the relationship between the results of AUSRIVAS monitoring in the Cotter and elsewhere in the ACT, and possible effects of differences in the flow regime. Moreover, the design of the monitoring program is insufficient to allow such an analysis. This is largely due to a focus on monitoring ACTEW’s environmental performance, rather than on the outcomes of adoption of the e-flow provisions under the 1999 EFG.

The fish sampling results have been described and, along with changes observed from previous sampling in the 1990s, have been interpreted in the light of flow-induced changes (Lintermans 2004).

The results from the monitoring can be summarised as follows.

Cotter system: Benthic macroinvertebrate assemblages have been sustained at or above

ACTEW’s AUSRIVAS ‘performance criteria’ levels stipulated under Schedule 1 of Licence No. WU67 (bands B or C just below dams, band A well below dams; see Appendix B for description of AUSRIVAS bands), except at Vanities Crossing.

Macquarie Perch (in Cotter C only) and Blackfish recruitment were sustained during the drought and following the fires.

In-channel habitat degradation due to sedimentation has been significant in the lower Cotter (upstream of and below Vanities Crossing), with some amelioration due to tributary flows.

Queanbeyan R below Googong: AUSRIVAS and fish sampling indicate that this system has been sustained at

or above ACTEW’s AUSRIVAS ‘performance criteria’ levels (bands B or C), maintaining impoverished benthic macroinvertebrate and fish assemblages, both before and during the drought.

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Other reaches in the ACT:The monitoring data are insufficient for an interpretation of the biological value of e-flows in other systems. All monitoring sites were reported as being affected by low flows during the drought, coupled with poor water quality and other impacts (urbanisation), with sites in Ginninderra Creek, the lower Molonglo and the Murrumbidgee Rivers all being in poor biological condition (Environment ACT 2003). The monitoring site in the Gudgenby River was also moderately biologically impaired during the drought. The sampling design at these sites was not appropriate for an assessment of the relative roles of flows or water quality in the resulting environmental condition of these reaches.

3.2 R&D activitiesA significant body of research was conducted in the Cotter River system during the period 2000 to 2004 (Chester 2003; Norris et al. 2004a; Chester and Norris in prep.), information from which was used in a number of adaptive management trials. This work was primarily focused on:

characterising the differences in macroinvertebrate and periphyton assemblages between sites below dams, in nearby unregulated tributaries and in nearby unregulated rivers (Chester 2003; Chester and Norris in prep; Norris et al. 2004a).

assessing the efficacy of the Cotter River ‘drought’ e-flow regime (point 8 section 2.2), and the potential for improving ecological outcomes with more effective use of e-flow releases, especially at Bendora dam (Norris et al. 2004a).

This work demonstrated that:Low flows, demonstrated needs & drought arrangements:

maintain relatively healthy benthic macroinvertebrate assemblages, i.e. in close to reference condition. Comparison with assemblages recovered in limited sampling before e-flows commenced (Marchant and Hehir 2002; Norris et al. 2004a) and from systematic sampling in the early years of the e-flows (Chester 2003) suggests a recent improvement in macroinvertebrate assemblages.

allowed the recovery in river condition after the January 2003 bushfires, although recovery was delayed compared to unregulated streams nearby. Recovery may also have been helped by reservoir spills and tributary inflows from local rainfall, which dwarfed e-flows in the gauge reported in Norris et al. (2004a).

maintained reduced habitat, FSS (fine surficial sediment) accumulation, and filamentous algal accumulation in the Cotter, even in the presence of the new e-flow regime, with possible consequences for food chains. Such effects are consistent with findings elsewhere (e.g. Allan 1995).

Variable flow releases: (between 10 and 30 ML/d, averaging 20 ML/d), may have significant

ecological benefits (e.g. filamentous algal decline). Trials to further evaluate this are planned for 2004–2005.

Flushing flows: the efficacy of the guideline prescribing the diversion and/or abstraction of

only 10% of the flow greater than the 80% exceedence flow cannot be assessed.

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Short, low-level (<500 ML/d, mainly 150–250 ML/d) releases from Bendora Dam, i.e. not flushing flows as defined in the EFG:

successfully removed a large amount of sediment, deposited after rainfall and a reservoir spill, from riffles.

led to a gradual reduction in FSS on riffle stream-bed surfaces at sites downstream of Bendora Dam. FSS levels remained very high compared to measurements from an unburnt catchment, and higher than in an unregulated river from a burnt catchment. Calculations based on sediment transport models suggest that flows of around 50–150 ML/d in Cotter C should flush fine sediments from the surface of riffles, and the incidence of these flows has reportedly increased since e-flows commenced (Norris et al. 2004a).

may have redeposited sediments in downstream pools (Lintermans 2004) that are habitat for endangered fish. Higher flows may be needed to flush pools (see below and section 5.2).

may benefit periphyton communities, with flow-on effects to macroinvertebrates and fish.

Turbid releases: released from Bendora Dam to improve the water quality for drinking, along

with varying amounts of clear water to reduce downstream impacts, had no significant negative effects on benthic macroinvertebrates downstream.

With respect to the general ecology: shifts in the composition of periphyton and macroinvertebrate communities

may be linked. Where differences in macroinvertebrate assemblages between reference sites and sites below dams have been observed, these appear partly attributable to differences in their food source (periphyton).

the macroinvertebrate species negatively affected by regulated flows below dams are also a major food source for native fish.

research has only begun that directly links the needs of biota with flows in rivers of the ACT. Maddock et al. (2004) have linked habitat requirements of the Two-spined Blackfish to hydraulic habitat created by different flow levels at two sites in the Cotter River. More research is required before this work can be applied to managing flows in the Cotter River.

Conclusions about the effectiveness of low flows and flushing flows are confounded somewhat by a spill from the Bendora Dam in 2003 that dwarfed the e-flow releases. Therefore, successful maintenance of ecological condition cannot in all instances be solely attributed to e-flow regime.

Research is also underway to determine the level of flow required to flush sediments from pools in the lower Cotter River (Norm Mueller, Ecowise, pers. comm.). In theory, flows of around 500–1000 ML/d should flush excessive fine sediments from pools in this section of river. Field data have indicated that the releases from Bendora of 150–250 ML/d failed to remove FSS from pools unless they were enhanced by tributary inflows downstream of Bendora Dam. Successful flushing of pools reportedly occurred where tributary inputs enhanced environmental releases, bringing flow to a total of 600–800 Ml/d. These findings need to be confirmed in the final report for this research project before they can gain wide acceptance.

It was also noted (Chester 2003) that the operation of dams before environmental flows did not appear to affect the major ionic composition of water, nutrient levels,

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water quality or instream physical habitat (benthic sediments) (references cited in Chester and Norris in prep.), maintaining water quality within ANZECC & ARMCANZ (2000) guidelines for maintaining ecosystem health. This suggests that direct and indirect effects of flow might explain the poorer conditions prior to environmental flow releases (see ‘low flows’ above). However, cold-water releases may still have negative effects on biota, for example contributing to the failure for Macquarie Perch to spawn below some of the dams in the region (ACT Government 1999b).

3.3 Main messages for e-flow managementFrom the review of monitoring, research and compliance reporting activities above, the following conclusions can be drawn:

The e-flow regime in Cotter, comprising protection of low flows and flow arrangements under demonstrated need and droughts, has generally sustained the instream ecological condition at target levels, including during drought and following fires. It is not known to what extent the benefits observed are due to (or in spite of) tributary inflows and unmanaged reservoir spills that also occurred.

Poor (turbid) drinking water has been successfully released from the water supply storage into the Cotter River without evidence for harm to the environment.

The main ongoing risks to sustainability of ecological values in the Cotter River that might be addressed by an e-flow regime are the smothering of habitat (especially in pools), habitat reduction and flow effects on food chains.

Increasing the variability of low flows may provide ecological benefits in the Cotter River without altering the volume of environmental allocations, although this needs to be confirmed by research currently being undertaken.

The e-flow regime in the lower Queanbeyan River below Googong Dam has maintained this river’s condition during the drought, although this is usually significantly to severely impaired (see Appendix A for definitions of these river conditions).

Monitoring data are insufficient to assess the ecological benefits of e-flows in non-water supply river systems.

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4. Advice on appropriate approachesHere broad advice is provided on the appropriate approaches to determine the flows needed to sustain aquatic ecosystems in the ACT

4.1 Context for e-flow managementThe rivers of the ACT range in condition from being nearly pristine to highly degraded. They also have varying demands placed upon them, so ‘environmental’ management targets for rivers might vary in different parts of the catchment according to human uses. One way of balancing ecological with social and economic values is via the ‘healthy working river’ concept (Jones 2002 and 2003), where the values established for managing rivers reflect a compromise between a human use and the ecological demand. This concept allows realistic objectives to be set that should bring about improvements in the environment, and the maintenance of certain ecological values, while also maintaining social and economic values. It also means that a river that is classified as ‘moderately degraded’, in comparison to natural rivers, may still be considered a healthy working river, depending on its designated use (e.g. an urban stream needed for drainage).

4.2 Context of this reviewThere are a variety of methods for determining environmental flows (Arthington 1998, Arthington and Zalucki 1998). Arthington et al. (1998) have presented a ‘best practice’ framework for assessing environmental flows in river systems. It starts with preliminary desk studies compiling existing information about the focus area and an assessment of the ecological impacts of existing river regulation. This review contributes to these tasks, and could be used as one of the inputs to a broader process of environmental flow assessment. In addition, this review presents some draft ecological values and proposals about how e-flows might be changed, and some potential new e-flows are described. However, this is not meant to be a substitute for a more systematic formulation of environmental flow guidelines, as outlined in Arthington et al. (1998).

4.3 Use of Ecological ObjectivesThe EFG provide a degree of protection of key ecological values in the Cotter river system. A set of environmental values and policy aims and management goals has been articulated in the Territory Plan and the 1999 EFG (section 2.2). However, these values are broad, and have limited capacity to focus the use of e-flows as a management tool; more specific ecological and human use objectives are needed.

Protection of values in the Cotter River and other river reaches could be enhanced if water management is focused around a set of ecological objectives that are specific, quantifiable and outcome-focused. Such objectives may be based on the desire to protect species that are threatened or of high conservation priority, to protect the ecological condition or ‘health’ of river and wetland ecosystems, to sustain key ecological processes, and to maintain the physical integrity of river systems.

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ADVICEConsider adopting a process of:

setting ecological objectives for all river types and reaches in the ACT; identifying components of the flow regime which would be required to assist

achievement of these objectives, noting that achievement may be constrained by factors other than flow;

recommending e-flows and other management actions to achieve the objectives; and

conducting focused monitoring to allow assessment of performance against objectives.

4.4 Linking objectives to the flow regimeThe national benchmark in e-flow management requires identifying a flow regime, i.e. a pattern of flows, which influences or drives environmental condition (e.g. Arthington et al. 1998, Schofield and Burt 2003). An environmental flow regime comprises several components. The components include low flows and flow events, with defined magnitudes, timing, durations, frequencies, seasonal pattern, return intervals and rates of rise and fall.

The 1999 EFG identify three flow regime components - low flows, flushing flows and spawning flows - with varying rules associated with their deployment. The EFG implicitly recognise the need for varying flow regime components, but do not tie them to specific ecological objectives, outcomes or river reaches.

ADVICEOnce the specific objectives have been identified for each river system or reach, the flow regime components required for achievement of each objective could be identified. This will require more detailed hydraulic and biological analyses than can be undertaken during this review. Typically the timing, magnitude, duration and/or frequency of components could be described. A level of confidence could also be ascribed to the knowledge on which the recommendation of the component is based. See Arthington et al. (1998) for a ‘best practice’ framework for assessing environmental flows. Trade-offs with human use and other objectives would also need to be considered.

4.5 Monitoring & adaptive management

Once the objectives are identified and the e-flows have been implemented, a monitoring program should be commenced. The monitoring program must specifically address the ecological objectives, and be able to demonstrate, preferably with quantifiable confidence levels, whether the objectives have been achieved or not, and the degree of change associated with implementation of e-flows.

Licence conditions imposed on ACTEW by the ACT Government (Schedule 1 of Licence No. WU67) require monitoring of environmental indicators with reporting against performance objectives and criteria, as shown in Table 1 (section 2). A monitoring program is required, with sampling of fish, macroinvertebrates, water quality and geomorphology at prescribed intervals (e.g. twice yearly for

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macroinvertebrates, biennially for fish). While not all indicators have been reported against these criteria to date, these requirements represent a valuable monitoring and performance assessment framework.

ADVICEAssessment would be needed to show if the ecological objectives have been achieved.

The existing monitoring program could be continued, and linked to other ecological and water quality objectives (besides current performance objectives) that are explicitly defined.

A monitoring program could be considered for all waters outside of the water supply catchments (the Cotter and Queanbeyan rivers).

The principles for a monitoring program, and its relation to adaptive management, are outlined in section 7.

4.6 Linking e-flows restorations to refuge habitatsLinking to refugesConnectivity along aquatic corridors and between aquatic refuges is a key long-term biodiversity conservation issue (e.g. Bond and Lake 2004, Bond and Lake in press), especially with regards to droughts, and there is limited focus on this in the EFG. Aquatic refuges in the ACT include deep pools, backwaters, reservoirs, and the interstitial spaces between cobbles and boulders. The central objective for connectivity is to ensure that biota being managed using e-flows can access a refuge during disturbances (extreme events), and be able to return to the managed section following disturbance. Otherwise, long-term management efforts and trade-offs may be compromised once the next major disturbance occurs (Gore 1996, Bond and Lake 2004).

ADVICEConsider better incorporating access to refuges into e-flow management. Refuges, and barriers between refuges and managed stream sections, could be identified. Accessible refuges, or structures, or opportunities for biota to pass barriers, could be ensured.

As a minimum (i.e. for a moderate level of confidence), try to: Identify refuges (see Bond & Lake 2004 for types of refuges) and barriers

between refuges and managed stream sections by inspection of stream sections under a variety of flows (e.g. Figure 2).

Ensure there are accessible refuges, or structures (e.g. fish ladders) or opportunities for biota to pass barriers. One potential opportunity for fish to pass barriers is by drowning them out with an e-flow, although the success of this method for native fish is unknown.

Maintain water levels and water quality in pools and reservoirs following droughts and fires.

For greater certainty, identify major disturbances (e.g. drought, fire, introduction of alien fish or EHN virus), carry out a risk assessment for each disturbance and prepare

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recovery plans that anticipate the need for structures, or link dispersal opportunities to flow hydrographs, should a disturbance event occur.

Maintaining refugesEnvironmental flows can also be used to enhance natural refuges within channels.

ADVICEConsider managing flows to maintain refuges, targeting pool-filling and pool-flushing flows, and the management of reservoir water levels (as much as possible, balancing water supply needs) to maintain macrophyte beds.

Refuges can be maintained using flows as follows: Release low flows frequently enough to maintain deep pools as permanent

habitat (see below for suggested methods). Allow larger ‘bed disturbing’ floods to pass to allow for flushing of fine

sediments from the interstices of boulder and cobble beds. If possible set drawdown limits to maintain littoral habitat in reservoirs, which

are important refuges following disturbances. This may mean limiting the drawdown to approximately 2 m below the level of the spillway.

It is recognised that managing flows to sustain refuges may be quite costly and therefore not feasible in many places, but this needs to be taken into account in planning flow management.

Flushing flows help prevent the accumulation of fine sediments in pools, and help clear pools following a sedimentation event (e.g. after a fire). Flushing flows might be released from dams, possibly in conjunction with tributary inflows, following disturbances as follows:

Minimum: arbitrarily set the threshold for substantial accumulation of sediment at 20% of pool depth.

For greater certainty, substantial accumulation could be determined as follows:1. Calculate the relationship between depth & longevity of pools in droughts,

by regular observations after baseflows cease, or more crudely from maximum depth and pan evaporation data (this method may underestimate longevity, e.g. Hamilton et al. in press).

2. Estimate the longest period without baseflows using hydrographs and climatic records

3. Ensure that sedimentation does not reduce water depth to less than 50 cm of aquatic habitat during droughts, which is assumed to be adequate for the target species (this assumption needs to be tested by surveying pool refuges in droughts).

Flushing flows are discussed further in section 5.2.

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5. Existing flow extraction and e-flow componentsIn the current EFG there are four formal e-flow components specified, as well as other features of flows (e.g. extraction limits). This section presents an evaluation of the effectiveness of these e-flows or features of e-flows, based on the results of their application in the past few years, and also outlines changes that might promote sustainability of aquatic ecosystems. The advice is structured with reference to the degree of confidence (moderate or high) that the specified flow will be effective for protecting ecological values. Where appropriate, the advice is also split between water supply and non-water supply reaches since the information about these two kinds of river differs, as do the opportunities and responsibility for their management.

5.1 Low flowsAlthough periods of low-flow are an integral part of the life-cycle of some aquatic species (e.g. Humphries et al. 1999), they can represent periods of stress for many stream biota. Diversion of streamflow can lead to a greater incidence of zero flows, and more prolonged or lower discharge low flows (DNRE 2002). The effects of this are reviewed in, for example, Ward (1992; zero flows) and Gore (1996; low flows). In summary, during low flows there is a predictable shift from lotic (running water) to lentic (standing water) species in streams, a reduction in edge and riparian habitat (also see Maddock et al. 2004 for an example of this from the Cotter River), and a drop in numbers and biomass of macroinvertebrates and the fish that rely on them for food. Low flows may also advantage some alien species (Goldfish, Oriental Weatherloach, Eastern Gambusia) currently in Cotter reservoir, and Carp and Redfin Perch in Queanbeyan weir. Protection from extraction below a low flow level is therefore considered important to help sustain lotic stream communities.

Water supply reachesThe EFG low flow levels (supplemented by unmanaged reservoir spills) have provided demonstrable benefits for fish and macroinvertebrates in the Cotter River, and stable (but somewhat degraded) conditions in the Queanbeyan River (sections 3.1-3.2). Nevertheless, there is uncertainty about whether the benefits of the low-flow regime will be sustained because:

1) populations may be close to critical thresholds for survival;2) deleterious non-flow factors (e.g., from effects of fires, as described in Nelson

2003 and Norris et al. 2004a) may intensify, overriding the beneficial effects of flows; and

3) future unmanaged spills (which may have contributed to desirable conditions) are not guaranteed.

There are two apparent options for increasing confidence that ecological assets and river condition can be sustained:

1) by introducing greater variability in the low flows, with potential benefits as outlined in Norris et al. (2004a).

2) by defining low flows by a higher threshold (i.e. providing greater protection of low flows from extraction; DNRE 2002), assuming that this will preserve more lotic conditions and thus better sustain lotic biota.

A lower threshold for defining low flows will increase the risk that low flows fail to sustain ecological assets. It is thought (Norm Mueller, Ecowise, pers. comm.) that the

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method used for calculating the 80% exceedence flow threshold for low flows may cause the threshold value to drop over time as more records are used to make the calculation. There may be advantages to settling, instead, on a fixed threshold for defining low flows, but the demonstrable benefits of low flows outlined above only strictly apply to the low flows as defined by the 80% exceedence flow level in the past few years.

ADVICEMODERATE CONFIDENCE OF SUSTAINING VALUESMaintain low flows at current guideline levels to provide a moderate level of confidence that flora, fauna and ecosystem health will be sustained at present levels.

HIGH CONFIDENCE OF SUSTAINING VALUESFor greater confidence that low flows afford protection, consider carrying out an evaluation of the ecological benefit of:

1) introducing more variability in low flows downstream of dams (cf. Norris et al. 2004a), and2) setting a higher threshold for ‘low flows’ — higher than the 80% exceedence flow — in order to maintain key values (cf. DNRE 2002),

as part of an adaptive management framework or a systematic formulation of environmental flow guidelines (e.g. Arthington et al. 1998).

Non-water supply reachesThe monitoring data do not allow an assessment of the benefits of low flows outside of the water supply reaches. In modified and created systems some level of impairment could be expected from modifications to flow and other drivers of river condition affected by land use. Streams in poor condition are generally less able to sustain ecological assets. Should the present conditions be considered sub-optimal for sustaining ecological assets, there are at least two ways that ecological assets and river condition could be improved via adjustments to e-flows:

1) by setting a higher threshold for ‘low flows’ — higher than the 80% exceedence flow — in order to maintain key values (cf. DNRE 2002), assuming that this will preserve more lotic conditions and thus better sustain lotic biota.

2) by setting limits on daily extraction rates, which also have the effect of protecting low flows (DNRE 2002; see section 5.5).

ADVICEThe monitoring data do not allow an assessment of the benefits of low flows outside of the water supply reaches.

Consider monitoring and assessing the performance of EFG low flow provisions for non-water supply catchments.

5.2 Flushing flowsWater supply reachesIn the Cotter river system, trial low-level flushing flows (150-250 ML/d) lead to local flushing of fine sediments from riffles and appear to benefit periphyton communities (section 3.2), although these effects might also be an effect of unmanaged flows from

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local rainfall (both as reservoir spills and tributary inflows). Flushing of fine sediments from pools may require larger dam releases or augmentation of flushing flows with tributary inputs.

ADVICEMODERATE CONFIDENCE OF SUSTAINING VALUESThe following actions will result in a moderate level of confidence that flushing flows will sustain ecological values:

In Cotter reach C, between Bendora and Cotter Dams,:1) POOLS. Flushing events at 1:1.5-2.5 yr annual recurrence interval (as per 1999 EFG) to clear pools of FSS. It is recognized that this level is likely to be well above the flow actually needed, but reports of successful flushing at flows of 600-800 Ml/d need to be confirmed.2) RIFFLES. More frequent (trial 1/month), flushes of 150-250 ML/d to ensure riffles remain clear of fine sediments. Even lower flushes (50-100 ML/d) could improve riffle habitat, but will have a lower level of confidence attached until successfully trialled.

Other water supply reaches:1) POOLS. Flushing events at 1:1.5-2.5 yr annual recurrence interval (as per 1999 EFG) to clear pools of FSS. It is recognized that this level is likely to be well above the flow actually needed.2) RIFFLES Apply calculations used in Cotter trials (Norris et al. 2004a) to provide equivalent flushes in all water supply reaches downstream of dams (e.g. Cotter River below Cotter Dam, Googong Dam, Scrivener Dam, proposed new dams).

HIGH CONFIDENCE OF SUSTAINING VALUESFor greater confidence, the intensity of flushing events (magnitude and/or duration and/or frequency) could be modified after field monitoring and evaluation of trial or natural events, where unregulated flows, reservoir releases and tributary inputs are confidently gauged.

For convenience in discussions below, the various potential flushing flows will be designated by their midpoint flow level: i.e. flushing (200ML/d) = 150-250 ML/d; flushing (700ML/d) = 600-800 ML/d; and flushing (2 yr flood) = 1:1.5-2.5 yr annual recurrence interval flow.

Non-water supply reachesIt is not possible to evaluate the success of flushing flows outside of the Cotter system. Flows equivalent to the low-level flushing flows (200ML/d) reported to flush riffles in the Cotter River (and possibly pools; see section 3.2) would be well below the peak flow in streams, even where 10% of flow was extracted. However, channels in the region are often observed to be filled with sand to several metres depth, and effective flushing may be confounded by the introduction of sediments from upstream in the flows.

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ADVICEMODERATE CONFIDENCE OF SUSTAINING VALUESContinue with the present EFG for flushing flows (i.e. satisfied by limiting extraction of flows above the 80% exceedence flow to 10%). This should provide flushing for pools and riffles, recognizing that effective flushing may be confounded by the introduction of sediments from upstream in the flows.

HIGH CONFIDENCE OF SUSTAINING VALUESFor greater confidence, the intensity of flushing events (magnitude, duration, frequency) could be modified after field monitoring and evaluation of trial or natural events, where streamflows are confidently gauged.

5.3 Flows in droughtThe EFG (supplemented by unmanaged reservoir spills) have allowed fish and macroinvertebrates to survive and even breed in the Cotter River in the drought (sections 3.1, 3.2). However, uncertainty about the sustainability of this arises for the same reasons as given in section 5.1. In particular, in the very low ‘drought flows’ the risk is greater that populations are close to a threshold for survival, or may not be as resistant or resilient when faced with other kinds of disturbances.

ADVICEMODERATE CONFIDENCE OF SUSTAINING VALUESThe present flexible drought arrangements in the EFG provide a moderate level of confidence that existing ecological values will be sustained, particularly if they continue to be applied in an adaptive management framework (see section 7.2).

HIGH CONFIDENCE OF SUSTAINING VALUESFor greater confidence that ecological values will be sustained, consider upgrading drought flow rules for all water supply reaches to be equivalent to those operating in the Cotter. The Queanbeyan River downstream of Googong Dam receives a particularly low drought flow (2 ML/d vs 20ML/d in Cotter reach C, even though natural discharge for the Queanbeyan River is more than two times higher), and is likely to benefit ecologically from a higher allocation, particularly if significant ecological values are found to exist.

5.4 Special purpose flowsThe ‘Special Purpose Flow’ provisions under the EFG allow flows to be allocated for specific ecosystem requirements. The only Special Purpose Flows identified in the 1999 EFG were spawning flows for fish in the Cotter River (reach B). These have never been enacted, although an unmanaged reservoir spill of this size occurred once. However, both Macquarie Perch and Two-spined Blackfish spawned under existing catchment inflows and low flow - demonstrated need - drought flow arrangements (combined with unmanaged spills and tributary inflows) (section 3.1).

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ADVICEMODERATE CONFIDENCE OF SUSTAINING VALUESDiscontinue the flow regime rules currently identified for spawning flows in the Cotter system; there is moderate confidence that the existing low flow - demonstrated need arrangements are adequate for this purpose. The ‘drought flow’ levels may also be adequate but this needs to be confirmed by research disentangling the effects of unmanaged and ‘drought’ flows.

HIGH CONFIDENCE OF SUSTAINING VALUESFor greater confidence, adjust spawning flows in the Cotter River based on regular monitoring of recruitment success. Evaluate the need for spawning flows not only in the lower Cotter River, but also from Googong Dam and any new dams.

A variety of other ‘special purpose flows’ could be considered, e.g. for channel maintenance and bed disturbance, backwater connectivity, and riparian vegetation disturbance. Currently, channels downstream of dams are armoured and subject to infilling of substrate (Norris et al. 2004a), which reduces habitat quality for many stream biota. Periodic disturbance of the stream bed armour layer will assist in maintaining biological values. Flows required to disturb the stream bed armour layer downstream of dams should be identified, along with opportunities for their delivery and any associated risks downstream. Where feasible, based on releases, spills or a combination of both, conduct initial trials and assess results.

ADVICEConsider new Special Purpose Flows targeting backwater connectivity, fish passage (drowning out of barriers), maintenance of healthy riparian vegetation, bed disturbance (as distinct from flushing of bed surface), and other objectives as they arise (see section 6).

5.5 Maximum diversion limitsFor ungauged catchments in the ACT, ecological values are protected by e-flow rules that set maximum diversions at 10% of flow above the 80% exceedence flow. The e-flows monitoring data from the ACT do not allow an assessment of the adequacy of this for sustaining ecological values, and neither does the broader scientific literature. While it is clear that flow alterations have wide-ranging ecological effects (for example, in 83% of the 204 variables examined in 70 studies reviewed by Lloyd et al. 2003), there are few studies that can be used to establish thresholds, and from these no thresholds emerge (Lloyd et al. 2003). Therefore it is not possible to give clear scientific advice on whether an extraction level of 10% of flow will sustain ecological values in the ACT.

An alternative approach is to establish ecologically sustainable extraction limits, on the basis of protecting components of flow, where there is evidence or reasonable grounds to justify their protection. A recent example of this approach has been the sustainable diversion limit framework devised by the Victorian Department of Natural Resources and Environment (SDL; DNRE 2002), which is used to place limits on high-flow diversions from unregulated streams throughout Victoria. Using the SDL framework and available streamflow data, catchment and water resources managers

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can rapidly estimate the high-flow diversion potential of unregulated and generally ungauged streams.

In essence the SDL method is based on a series of premises that ecological sustainability will be promoted by:

1) preventing the unnatural occurrence of zero-flow periods or the extension of any natural zero-flow periods. These are particularly stressful to stream organisms adapted to flowing water (e.g. Ward 1992).

2) preventing an expansion of low flow periods, which are also considered as periods of higher environmental stress (see section 5.1 for justification).

3) keeping the extraction flow regime within the bounds of the natural flow regime by:

a. keeping it within the envelope characterised by flow-duration curves for all years except severe drought years;

b. restricting changes in the frequency and duration of flow events for any flow threshold;

c. restricting changes to the sequences of low flows and high flows.It is assumed that keeping the extraction flow regime within the natural range will preserve individual flow components or events that are critical to sustaining the native stream biota.

The SDL approach has found that diversion limits can be determined that are consistent with the premises for ecological sustainability by applying three rules:

1. Diversions should only occur over the period of high flows. This rule is similar to the current EFG, where there is a low flow limit below which extraction is not allowed, but it assumes that there is long-term seasonal variation in annual flows.

2. Within the high flow period, there is a minimum flow below which diversions should cease.

3. Within the high flow period, there is a maximum daily extraction rate.For the method of calculations, see DNRE (2002).

Using the SDL method, the maximum diversion rates in Victorian catchments average about the same rate as that allowed by the EFG for the ACT (i.e. 10% of high flows), but the diversion limit varies between catchments. The lowest diversion limits are less than 1% of high season flows, and the highest are in excess of 20%, depending on the estimated proportion of groundwater contribution and the permanence of streamflow (reflecting variations in catchment climate and physical characteristics). As well, a key strength of this approach is that the reliability of diversions can be estimated for water users.

The SDL approach and the current EFG are similar in that both target periods of higher flows for diversions, and both set limits on diversions. The SDL approach is more complicated, but rules within it are linked to more justifiable sustainability objectives, and SDL provides water users with better estimates of reliability of access to water.

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ADVICENeither monitoring data nor the broader scientific literature allow us to provide advice with even a moderate level of confidence on whether setting maximum diversions at 10% of flow above the 80% exceedence flow will sustain ecological values in the ACT.

In the longer term, a method that targets the conservation of key flow components could be more useful for setting maximum diversions than a uniform limit of maximum diversions of 10% of flow.

5.6 Groundwater extractionLow flows in streams come from baseflows, which are by definition derived from groundwater rather than overland flows of water, in contrast to ‘spells’ of higher flow, which contain elements of overland runoff entering streams. Baseflows account for a variable but significant amount of total stream flow (e.g. 14-98%, Newson 1994), depending on catchment geology. Extraction of shallow groundwater can therefore reduce the amount of baseflow entering streams, leading to a greater incidence of low-flows, or lower low-flow levels.

ADVICEIt is suggested that limits and monitoring be imposed on groundwater extraction to protect low flows in unregulated systems, for the same reasons that protection from excessive diversions of low flows is required to sustain stream health.

Monitoring for compliance of river flows with the e-flow provisions could include monitoring of groundwater extraction, which will potentially have a significant impact on river flows.

5.7 Drawdowns in urban lakesThe 1999 EFG specify a maximum drawdown for urban lakes and ponds of 0.2m below the level of the spillway, mainly to protect macrophyte beds. Macrophyte beds provide a number of benefits as aquatic habitat, and are sources of food for birds (Jeppesen et al. 1997). However there are no e-flow monitoring data to assess the performance of this guideline.

5.8 Responses to fireSpecial flow management is needed following extreme events, particularly bushfires. Sediment deposition and scouring arising from the January 2003 fires caused some impairment of the biota in the Cotter River, though equivalent impairment was evident in only a few of the reference sites.

There are two main issues that need to be managed relating to fire disturbance. These are (1) condition of the river (ecological), (2) water quality in supply dams (social/economic/ecological). The main ecological impacts that can be addressed by flows relate to the problems of sediment and organic matter deposition throughout the system, which smother substrate and can fill in pool habitat (needed especially for fish), and create low dissolved oxygen conditions. Flushing of fine sediment/organic matter from the riffle/shallow habitats can be done by sending an e-flow dam release

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through the system. However, flushing out the pools will require a larger flushing flow and an e-flow will need to be piggy-backed on a natural flood event to induce a flow big enough for this purpose (see flushing flows, section 5.2).

In instances where organic matter and sediment input into storages has occurred, it may be necessary to release the bottom layer of storage water to protect water quality in the rest of the storage, as in the recent drought. In such cases the impact of the release of this water (and its poor quality) on downstream biota should be considered. In instances where the water released has a large amount of fine sediment/organic matter, one option to protect the environment is to release a pre and post flush with clean water to protect environment. This tactic was employed in managing water quality of the previous fire impacts with apparent success (section 3.2). However, the release of cooler bottom water could have significant thermal impacts downstream, so such releases should be avoided if possible in spawning seasons.

ADVICEThe adaptive, flexible and collaborative approach taken to managing flows following the recent fires and drought in the ACT could be continued and formalised.

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6. Potential new objectives and e-flows

6.1 Draft values & objectives identified at workshopThe purpose of setting objectives is to better focus the identification of environmental flows, as components of the flow regime, in order to maintain the ecological values. In addition, the objectives, if quantified, can be used to assess the success of environmental flow management, through monitoring targeted at objectives.

Before addressing specific objectives, in the EFG the Cotter system was divided into three reaches as outlined in section 2.2.

Multiple impacts to the channel below Cotter Dam (e.g. alien fish, substrate armouring, EHN virus) compared to above the dam might require a different set of ecological objectives for this reach. In addition, any changes to the mode of operation of Cotter Dam may require formulation of a different environmental flow release strategy for the downstream reaches.

ADVICEConsider dividing Cotter C as follows for e-flows management:Cotter C1 below water offtake, Bendora to Cotter corridorCotter C2 below water offtake, Cotter Dam to Murrumbidgee confluence

An initial set of river ecological objectives was proposed during a workshop held in October 2004, attended by staff of the CRCFE, University of Canberra, Freshwater Systems, Environment ACT, ACTEW and Ecowise. The objectives have been modified following further consideration, and are shown in Table 3. The scientific justification for the objectives can be found in section 6.2.

ADVICEConsider incorporating the set of river ecological objectives in Table 3 into the EFG. These would elucidate the values identified in Schedule 1, Appendix 1 of the Territory Plan.

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Table 3. Draft water ecological values for management, ecological objectives and flows to target objectives for rivers in the ACT. Where the level of uncertainty is high, the advice is to “trial” an objective or flow (see section 6.4 for an explanation). It is recognised that the water requirements or downstream risks posed by the flow levels may not be sustainable once water supply and other social or economic factors are considered. In this case the flow levels provide an indication of trade-offs needed to achieve ecological objectives.

Value Objective Location Flow regime component(see section 5 for details)

Further work needed or (notes)

Macquarie Perch

Maintain populations by ensuring recruitment is sufficient: trial young of year (YOY) fish comprise >30% of the monitoring catch, and catch is >40 fish per standard monitoring effort.

Maintain riffle sediment surface clear of fine surficial sediment (FSS),

and pools clear of FSS deposits in excess of 80% of depth.

Cotter C1(note that they are not thought to be present in Cotter A, B)

Trial low flows drought arrangements as per EFG

Flushing flows (200ML/d, or trial 50-100 Ml/d) once a month in natural low-flow periods

Flushing flows (2 yr floods); consider major releases to clear pools after sedimentation events.

Assess efficacy of YOY recruit-ment targets; see section 6.2.

Assess effect of riffle flushing on quality of pool habitat for M. perch (Lintermans 2004).

Assess effectiveness of lower flows, e.g. 500-1000 ML/d, to remove FSS.

Macquarie Perch

Persistent populations (recognising that there are multiple stressors in this reach).

Maintain riffle sediment surface clear of FSS, and pools clear of FSS deposits in excess of 80% of depth.

Cotter C2 As in Cotter C1 As in Cotter C1

Blackfish Maintain populations by ensuring recruitment is sufficient: trial YOY and 1+ fish comprise >40% of the monitoring catch and catch is > 80 fish per standard monitoring effort (note that YOY are poorly recovered by standard sampling methods).

Maintain riffle sediment surface clear of FSS.

Cotter A, B & C1 Trial low flows drought arrangements as per EFG

Flushing flows (200ML/d, or trial 50-100 Ml/d) once a month in natural low-flow periods.

Assess efficacy of YOY & 1+ recruitment targets; see section 6.2.

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Cotter River frog

Maintain population numbers and distribution (measured by census call monitoring)

Cotter A & B Trial ensuring that backwater pools are flooded in spring; trial one bankfull flow every spring.

Trial minimising summer flushing events for backwater pools.

Identify flows required to connect lateral backwater habitats.

Healthy ecosystems

Maintain healthy benthic macroinvertebrate assemblages - Maintain all AUSRIVAS scores: within those ranges (bands) defined under

ACTEW licence;

within the reference or A band

within bands to be agreed by ACT government

Maintain healthy benthic macroinvertebrate populations – Trial maintaining the total macroinvertebrate density and population abundance for each reach as close as possible to those observed in appropriate reference reach (pristine or impaired, cf. Appendix B).

water supply eco-systems/ reaches

natural ecosystems

modified ecosystems (except water supply reaches)

all reaches

Low flows drought arrangements as per EFG, but with periodic variation within the month (by +/- 50%). Flushing flows (200 ML/d).

Low flows & flushing flows (2 yr flood) – protect with extraction limits as per EFG.

Low flows & flushing flows (2 yr flood) – protect with extraction limits as per EFG.

Trial low flows drought arrangements as per EFG, but increase toward median monthly flows when possible.

Trial substrate disturbance flows: allow largest floods to spill or pass downstream.

(Flow not the only driver in some systems).

(Higher flows are needed to increase habitat, i.e. wetted area). Assess population size and relationship with flow and wetted area. Define target abundance relative to reference reach(es).

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Healthy ecosystems (continued)

Non-dominance (trial <20% cover) of filamentous algae for (trial) 95% of time

Stream form – Maintain pool-riffle vertical profiles by preventing channel incision & sediment deposition in pools to >20% of total depth at baseflow, and

Protect from excessive (compared to natural) flood peaks

Prevent build up of fine sediments on surfaces and in interstices.

Natural eco-systems, Cotter A, B, C; Queanbeyan R below Googong Dam

Natural, Cotter A, B, C, Queanbeayan R below Googong Dam

Cotter A

Natural, Cotter A, B, C, Queanbeayan R below Googong Dam

Low flows drought arrangements as per EFG, but with periodic variation within the month in regulated reaches (by +/- 50%).

Cotter B/C: flushing flows (200 ML/d)

other reaches: trial flushing flows (2 yr flood) as per EFG.

Cotter B/C: trial flushing flows (700 ML/d)Other reaches: trial flushing flows (2 yr flood)

Trial substrate disturbance flows: allow larger floods to spill or pass downstream.

Trial keep flows downstream of (proposed) interbasin transfers within natural flow regime envelope.

Flushing flows (200 ML/d): Cotter B/C, but with periodic variation within the month (by +/- 50%); other reaches as per EFG (2 yr flood).

Adjust (probably downwards) after trialling.

Assess channel forming flood and bed disturbance flood sizes for Cotter A, C, Queanbeyan downstream Googong and Scrivener Dams. Identify opportunities to deliver, and any downstream risks.

Assess needs for higher flushing flows to remove fine sediments in other systems.

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CRC Freshwater Ecology ACT e-flows guidelines review

6.2 Science underpinning draft objectivesThe science underpinning the ecological objectives, and the environmental flows to achieve them, is summarised here. The environmental flows information (in italics) has been surmised from a review of the literature.

Macquarie PerchThe biology and status of Macquarie Perch in the ACT have been thoroughly reviewed in Lintermans (2002) and ACT Government (1999b). Macquarie Perch is a threatened species in the ACT and nationally. Key aspects of its biology related to flow, and potential environmental flows benefits, are: It releases eggs that lodge in riffle gravels and cobbles. It therefore requires clean

riffle gravels for spawning. Flushing flows may be needed to remove fine surficial sediments (FSS).

It prefers deep, rocky pools. Flushing flows that clear pools of sediment may be required if sedimentation events occur, e.g. as has happened following recent fires.

It has difficulty passing through relatively low-level stream barriers. Environmental flows might be required to drown out barriers.

It uses rising water temperatures as a cue for spawning, and cold bottom-water releases from dams inhibit spawning. Cold water releases should be minimised.

Although recruitment is required to sustain the fish populations, the scientific basis is not well established for the size and composition of the catch specified in Table 3 for Macquarie Perch. If the objectives in Table 3 are adopted, monitoring and assessment should be undertaken to determine if these levels of recruitment are adequate, or even more than is needed for sustainability.

Two-spined BlackfishThe biology and status of Two-spined Blackfish in the ACT have been thoroughly reviewed in Lintermans (1998, 2002) and ACT Government (1999a). Two-spined Blackfish is a threatened species in the ACT. Key aspects of its biology related to flow, and potential environmental flows benefits, are: It shelters in the interstices of boulder and cobble riffle beds, and is suspected to

lay adhesive eggs on the underside of boulders or cobbles. Flushing flows to keep the bed clear of sediment infill may enhance the survival.

It may use rising water temperatures as a cue for spawning, so that cold bottom-water releases from dams might inhibit spawning. Cold water releases should be minimised.

The comments about recruitment targets for Macquarie Perch apply equally to Two-spined Blackfish.

Leaf-green Tree Frog (Cotter River Form)The Cotter River form of the Leaf-green Tree Frog (Litoria nudidigitus), known as the Cotter River Frog, is described by Gillespie and Osborne (1994). The Cotter River Frog is strikingly different from the rest of the species (Osborne et al. 1994). As well, this population is now apparently confined to the Cotter River upstream of Bendora Dam (Osborne unpublished). It is therefore of considerable regional significance. Key

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aspects of its biology related to flow, and potential environmental flows benefits, are (also see Appendix C):

It breeds in streamside pools (Hero and Gillespie 1993; Holloway 1997). Flooding of semi-detached streamside pools in spring may be needed to provide breeding sites.

High stream flows during the warmer months are likely to impact upon riverine frog populations by flushing eggs and larvae downstream (Gillespie and Hines 1999; Gillespie and Hollis 1996). As well, trout are effective predators of the Cotter River Frog (Gillespie 2001) and may gain access to streamside pools during inundation. High stream flows (above natural peaks and frequencies) should be minimised during the period when eggs and tadpoles are present.

Healthy Ecosystems — algaeAn over-dominance of filamentous algae has flow-on effects to macroinvertebrates (Allan 1995; Chester 2003) and fauna that feed on them (e.g. fish). In addition algal growth during periods of low flow can trap sediment and accumulate organic matter that can eventually degrade both water quality and physical habitat used by fish and invertebrates (Allan 1995, Norris et al. 2004a). Key aspects of algae related to flow, and potential environmental flows benefits, are:

Natural flushing flows clean surface and interstices of sediment and prevent the build-up of filamentous algae (Allan 1995; Norris et al. 2004a). Flushing flows below dams may reduce the build-up of filamentous algae and FSS (e.g. Norris et al. 2004a).

Constant flow levels (reduced flow variability) favour shifts in the algal community to filamentous forms (Allan 1995, Norris et al. 2004a). Variation in low flows below dams may reduce shifts to filamentous forms of algae (e.g. Norris et al. 2004a).

Healthy Ecosystems — fine surficial sediment (FSS) depositionThe buildup of fine surficial sediments in riffles reduces the area of the stream bed where healthy biofilm and macroinvertebrate communities can develop (and provide food for fish). This problem has been particularly acute in the Cotter and adjacent catchments following the recent fires (e.g. Nelson 2003, Norris et al. 2004a). Flushing flows are the key to preventing the build-up of FSS (Norris et al. 2004a).

Healthy Ecosystems — channel formGross channel form (i.e. ‘channel types’) is influenced by a number of factors related to stream flow: stream power, sediment supply, and the competence of channel flows to move sand, gravel, cobbles and boulders (Young et al. 2002). There are two main features of channel types in the ACT that it might be possible to manage using e-flows: (1) the burial of channels by sediments, often to several metres depth, and (2) channel incision.

The smothering of channels with sediments reduces habitat quality and the number and depth of refuges in streams (Bond and Lake 2004, in press). Sediment deposition may occur if flows are not sufficient to remove material introduced into streams. This situation is an extreme version of the problem of deposition of FSS, although the sediments may have been mobilised as a result of land use rather than fires (Scott 2001). As for FSS, flushing flows are the key to sediment removal (see section 5.2),

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although sediments brought in by flows from upstream may confound the ‘flushing’ effects of sediment removal.

Channel incision will mainly be an issue in valleys where there is a degree of floodplain development, reflecting long-term (e.g. 1000+ years) sediment deposition; otherwise channels will not have sediments to be incised. Incised channels are usually observed to have less bed sediments (although they may be partially filled with sand) and flatter profiles, representing more degraded habitat than unincised channels (Ralph Ogden pers. obs.). Channel incision is thought to be controlled in part by stream power (Watson et al. 2002). There is therefore a risk that channels will be incised if flows are augmented by inflows from interbasin transfers. ‘Environmental flows’ in such rivers should aim to allow transmission of extra water while minimizing channel erosion and incision.

Potential environmental flows benefits are: Flushing flows to help prevent smothering of pools and riffles with sediments. In instances where inter-basin transfers may occur, restoring the flow to match

the natural flow regime may minimize impact of increased stream power (cf. DNRE 2002). However, further investigation of this is needed.

6.3 Other potential objectivesThis review was not able to fully quantify all the objectives identified by workshop participants. There are other factors and species that are valuable in themselves, or important to the ecology of the region’s streams, for which the development of objectives should be considered, including platypus, water rats, waterbirds, tortoises, riparian vegetation communities, and ecosystem measures like production to respiration ratios. However, at present there is insufficient ecological knowledge to set environmental flow objectives for them, as either the status of their populations/communities is poorly understood, or their environmental flow requirements are unknown or poorly understood.

ADVICEEcological objectives could be further refined and quantified where possible. This could be done by the review of current local and scientific knowledge and the introduction of trial values or ranges for each objective, against which monitoring data can be reported.

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6.4. Flow regime needed to satisfy objectivesPotential environmental flows have been identified to be applied to achieve each ecological objective (Table 3). While it is well established that flow alterations affect streams (Lloyd et al. 2003), there is usually only a moderate level of confidence that a particular environmental flow will lead to a specific ecological outcome in streams and rivers of the ACT. The EFG have only been in operation for a few years, during which a significant drought and sever bushfires have occurred. This, coupled with an absence of monitoring except in the water supply reaches, and frequently a lag in ecological responses to changes in flow regimes, has limited the build up new knowledge about the relationships between e-flows and ecological outcomes and assessment of the degree to which the EFG have been effective.

Where there is a high degree of uncertainty, the advice is to ‘trial’ a flow or objective (Table 3). There is naturally only a low level of confidence that the trial flows selected are right for the objective. It is expected that (if adopted) these e-flows can be refined through adaptive management (section 7.2). It is therefore suggested that only incremental adjustments be made to the EFG, based on new knowledge as it accumulates.

At least two of the new flow regime components could be classed as Special Purpose Flows under the EFG:

channel maintenance/bed disturbance flows for healthy ecosystems; backwater flows for maintaining Cotter River Frog populations.

ADVICEConsider the set of established and ‘trial’ environmental flows in Table 3 for incorporation into the EFG.

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7. Advice on monitoring & adaptive management

7.1 Monitoring programThe monitoring program undertaken by ACTEW in water supply reaches is to assist:

in determining the effectiveness of the provision of environmental flows and to provide information for the five year review of the ACT EFG; and

in determining the impact of increases in water use from each of the water supply catchments covered by licence.

Monitoring of stream reaches associated with ACTEW water supply infrastructure (Schedule 1 of the licence) has provided some useful information, while other aquatic ecosystems have not been monitored enough to assess the effects of the EFG. The level of monitoring conducted needs to be increased to allow fuller assessment of the ecological outcomes of the e-flow management in the ACT.

The monitoring program should also be reviewed in the light of any new environmental flow targets set. Schedule 1 of the ACTEW licence outlines the management objectives, performance indicators and criteria against which the effectiveness of the current environmental flows regime may be assessed (see sections 2 and 4.5). However, the importance of establishing causality between changes to the flow regime and ecological response is not clear from Schedule 1. The study design that has been adopted (e.g. BACI, or beyond BACI) is also not clear.

A generic environmental flow-monitoring framework is currently being developed by the CRC for Freshwater Ecology. The framework is consistent with approaches such as those outlined by the Australian Water Quality Monitoring Guidelines (ANZECC & ARMCANZ 2000) and Downes et al. (2002) for detecting ecological impacts. A key feature of this new framework is the incorporation of a Multiple Levels & Lines of Evidence (MLLE) approach (Norris et al. 2004b) that assists in defining the objectives, conceptual understanding and performance indicators of a monitoring and assessment program, as follows:

1. Define the scope of the project and its objectives2. Define the conceptual understanding of flow–ecology relationships and the

questions (hypotheses) to be tested (includes formal MLLE assessment steps)3. Select variables to be monitored 4. Determine study design, accounting for the specific activities and location

(e.g. availability of control and reference locations)5. Optimise study design and agree on the effect size to be detected6. Implement the study design7. Assess whether the environmental flows have met specific objectives and

review conceptual understanding and hypotheses.

The MLLE approach embedded in the generic environmental flow monitoring framework was adapted from the steps identified by Downes et al. (2002) and is explained in more detail in Appendix D. It can be summarised as follows:

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Question(s) & Conceptual model

Relevant lines of evidence

•Literature review•Assemble and analyse local data

Additional lines of evidence

Weight all literature and local data relative to quality Verdict

Characteristics of human activityCharacteristics of impact location

From examination of Schedule 1 to the ACTEW Licence for water supply reaches, it is evident that many of the key steps included in the generic environmental flows monitoring framework currently being developed by the CRCFE were also considered when preparing the current monitoring program, although some aspects such as the conceptual underpinning and study design were not made explicit. It should also be noted that the level of detail provided under Schedule 1 of the ACTEW licence is not reflected in monitoring conducted in other reaches in the ACT.

Any review of current monitoring arrangements should consider (re-)confirming the conceptual basis of the proposed environmental flow objectives, its relationship to the objectives of the monitoring program, and the level of evidence available to support inclusion of the performance indicators or metrics. Table 4.1 of the Schedule 1 monitoring program shows performance targets and effect sizes for macroinvertebrates. Suitable targets and effect sizes should also be included for other performance indicators such as channel sediment grading, fish populations and other habitat and ecological process features. For example, what evidence of population size will be required to convince stakeholders that environmental flows have resulted in successful spawning events for threatened fish species, as indicated in Table 4.1 of the Schedule 1 monitoring program? What habitat area of wetted streambed is required for macroinvertebrates?

All monitoring and assessment programs should include analysis of the collected data and comparison of results with the outcomes predicted by the environmental flow objectives, preferably within an adaptive management cycle. The data collected by the existing monitoring program have been extremely valuable to water managers. It is suggested that current arrangements — namely, regular analysis of data, and meetings to consider the implications of results — continue in the future.

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ADVICEMore informed management of e-flows will require improvements in the overall design and conduct of monitoring of environmental outcomes. Consider a more intensive, rigorous and detailed monitoring program in non water-supply catchments, along the line of that in water supply catchments.

If the existing environmental flow objectives (section 2.1 and table 1) are refined or restated (see sections 4.3 and 6), they could then be used to develop specific targets that could be measured as part of the monitoring program.

7.2 Adaptive managementAdaptive management is a systematic process for improving management policies and practices by learning from the outcomes of operational programs. Adaptive management principles are embedded in the 1999 EFG, and have been further developed in practice). The principles worked well in the Cotter River during 2003–2004 in relation to setting e-flows during drought and under a demonstrated needs scenario, as well as in relation to capturing new information. During this time, minimum flows were reduced without causing undue harm to the aquatic environment; variability was introduced to minimum flows on a trial basis, and flushing and turbid releases were actively managed. This adaptive management occurred in conjunction with monitoring and assessment, generating new understanding of ecosystem responses and the potential for ‘smarter’ e-flow management. Continuation of knowledge-based adaptive management of water resources in the ACT would be of benefit, strongly focused around new ecological objectives, should they be developed or adopted.

An adaptive management approach in the EFG should ideally regard the e-flow prescriptions as ‘experiments’ that result in measured responses in ACT river ecosystems. Such an experimental emphasis is called "active" adaptive management (Walters and Holling 1990). Once the e-flow monitoring program has been revised (focused around the objectives), a regular process of reporting against the objectives should take place, accompanied by expert opinion about the reasons for the trends and results from the monitoring, the whole, preferably, being centrally coordinated. This information should then be reviewed, preferably annually, and consideration given to adjustments to e-flow magnitudes, timing, or methods of delivery. Any trials should be accompanied by additional R&D where necessary to address key knowledge gaps. The information from this process should then form the basis of future formal review of the EFG, for which a frequency of every five years seems appropriate. It should also be used to update the objectives and their quantitative definitions.

In addition, acceptable bounds for compliance with e-flow prescriptions should be identified. Currently, compliance with e-flows by ACTEW appears high (see ACTEW 2001-03), aided by the use of the ‘demonstrated needs’ and drought flow provisions. Compliance with EFG surface water abstraction limits outside the water supply catchments is harder to assess, due to the absence of data relating the level of abstraction to the 80% exceedence flow threshold for each reach. This is compounded by the fact that e-flows compliance reporting does not include any information on groundwater abstraction and its effects on baseflows. The five yearly review of the EFG should also assess the degree to which compliance can be flexible, within the

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constraints of achieving the objectives. The degree to which any compliance failures lead to failure to achieve the ecological objectives will only emerge with time (and data).

ADVICEContinue the integration of e-flow management, monitoring and assessment, within an adaptive management environment. Also consider having a clear formalisation of an active adaptive management strategy in the EFG.

A formal review of the EFG could continue to occur every five years. It could also be used to update the objectives and their quantitative definitions. Acceptable bounds for compliance with e-flow prescriptions could be identified.

Stream and groundwater diversions need to be recorded and collated into a form useful for monitoring before the effects of such diversions can be assessed in comparison to e-flow objectives.

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8. ReferencesACTEW (2001-2003). Environmental Flows, Annual Compliance Reports. Reports to ACT

government. – October 2001, October 2002, October 2003.

ACT Government (1999a). Two-spined Blackfish (Gadopsis bispinosus): a vulnerable species. Action Plan No. 11. Environment ACT, Canberra.

ACT Government (1999b). Macquarie Perch (Macquaria australasica): an endangered species. Action Plan No. 13. Environment ACT, Canberra.

ACT Government (1999c). Environmental flow guidelines. Environment ACT, Canberra.

Allan, J.D. (1995). Stream ecology. Structure and function of running waters. Kluwer Academic Publishers, Dordrecht.

ANZECC and ARMCANZ (2000). Australian guidelines for water quality monitoring and reporting. Australian & New Zealand Environment and Conservation Council and the Agriculture and Resource Management Council of Australia & New Zealand. http://www.deh.gov.au/water/quality/nwqms/pubs/mg-contents.pdf

Arthington A.H. (1998). Comparative evaluation of environmental flow assessment techniques: review of holistic methodologies. Land and Water Resources R&D Corporation Occasional Paper No. 26/98, 46 pp.

Arthington A.H. and Zalucki, J.M. (eds) (1998). Comparative evaluation of environmental flow assessment techniques: review of methods. Land and Water Resources R&D Corporation Occasional Paper No. 27/98, 141 pp.

Arthington A.H., Brizga S.O. and Kennard, M.O. (1998). Comparative evaluation of environmental flow assessment techniques: Best Practice Framework. Land and Water Resources R&D Corporation Occasional Paper No. 25/98, 26 pp.

Bond, N. and Lake, P.S. (2004). Disturbance regimes and stream restoration: the importance of restoring refugia. Fourth Australian Stream Management Conference Proceedings.

Bond, N. and Lake, P. S. (in press). Ecological restoration and large-scale ecological disturbance: the effects of drought on the response by fish to a habitat restoration experiment. Restoration Ecology.

Chester, H.L. (2003). Dams and flow in the Cotter River: effects on instream trophic structure and benthic metabolism. Unpublished Honous thesis, University of Canberra.

Chester, H.L. and Norris, R. (in prep.). Dams and flow in the Cotter River: effects on instream trophic structure and benthic metabolism. Manuscript in preparation.

Downes B., Barmuta L., Fairweather P., Faith D., Keough M., Lake P.S., Mapstone B. and Quinn G. (2002). Monitoring ecological impacts: concepts and practice in flowing waters. Cambridge University Press, UK.

DNRE 2002. Recommendations for Sustainable Diversions Limits over Winterfill Periods in Unregulated Victorian Catchments. Report prepared by SKM and the CRC Freshwater Ecology for the State of Victoria, Department of Natural Resources and Environment, Melbourne.

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Ecowise 2001-2003. Environmental Flows Quarterly Reports: Autumn 2001, Spring 2001, Autumn 2002, Spring 2002, Autumn 2003, Spring 2003. Ecowise/ACTEW, ACT.

Environment ACT (2003). ACT water report 2002-2003. ACT Government, Canberra, 64pp.

Gillespie, G.R. (2001). The role of introduced trout in the decline of the spotted tree frog (Litoria spenceri) in southeastern Australia. Biological Conservation 100:187-198.

Gillespie, G. and Hines, H. (1999) Status of temperate Riverine frogs in South-eastern Australia. Pp 109-130 In Campbell (ed) Declines and disappearances of Australian frogs. Environment Australia, Canberra.

Gillespie G. R. and Hollis, G. J. (1996). Distribution and habitat of the spotted tree frog, Litoria spenceri, (Anura: Hylidae), and an assessment of potential causes of population declines. Wildlife Research, 23, 49-75.

Gore, J.A. (1996). Responses of aquatic biota to hydrological change. Pp. 209-230 in: Petts, G., and Calow, P. (eds.) River biota: diversity and dynamics. Selected extracts from the Rivers Handbook. Blackwell Science Ltd., Oxford.

Hamilton, S. K., Bunn, S. E., Thoms, M.C., Marshall, J.C. (in press) Persistence of aquatic refugia between flow pulses in a dryland river system (Cooper Creek, Australia). Limnology and Oceanography.

Hero, J-M. and Gillespie, G. (1993) the tadpole of Litoria phyllochroa (Anura: Hylidae). Proceedings of the Royal Society of Victoria 105: 31-38.

Hogg, D. and Wicks, B.A. (1989). The aquatic ecological resources of the Australian Capital Territory. National Capital Development Commission. David Hogg Pty. Ltd. Canberra.

Holloway, S. (1997). Survey protocols for the stream-breeding frogs of far East Gippsland: the application of habitat modelling and an assessment of techniques. Master of Applied Science thesis, Applied Ecology Research Group, University of Canberra.

Humphries P. King A. and Koehn J. (1999). Fish, flows and flood plains: links between freshwater fishes and their environment in the Murray-Darling River system, Australia. Environmental Biology of Fishes 56, pp. 129-151.

Hunter, D. and Gillespie, G. R. (1999). The distribution abundance and conservation status of River in frogs in Kosciusko National Park. Australian Zoologist 31: 198-209.

Jeppesen E., Søndergaard Ma., Søndergaard Mo. and Christoffersen K. (eds) (1997). The structuring role of submerged macrophytes in lakes. Springer, New York, 423 pp.

Jones, G. (2002). Setting environmental flows to sustain a healthy working river. Watershed, February 2002, CRC for Freshwater Ecology, pp. 1-2.

Jones, G. (2003). Healthy working rivers: balancing scientific and community values. Watershed, May 2003, CRC for Freshwater Ecology, pp. 1-3.

Lintermans, M. 1998. The Ecology of the Two-spined Blackfish Gadopsis bispinosus (Pisces: Gadopsidae). Unpublished MSc. thesis, Division of Botany and Zoology, Australian National University.

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Lintermans, M. (2002). Fish in the upper Murrumbidgee catchment: a review of current knowledge. Environment ACT, Canberra, 92pp.

Lintermans M. (2004a). Monitoring Program to Assess the Effectiveness of Environmental Flows in the Cotter and Queanbeyan rivers in 2003, and to assess the impacts of the 2003-04 drought-flows on recruitment of Gadopsis bispinosus and Macquaria australasica. Report to ACTEW Corporation. July 2004. Wildlife Research and Monitoring, Environment ACT, Lyneham ACT. 43 pp.

Lintermans, M. and Osborne, W. (2002). Wet and Wild. Field guide to the freshwater animals of the Southern Tablelands and high country of the ACT and NSW. Environment ACT, Canberra.

Lloyd N. Quinn G., Thoms M., Arthington A., Gawne B., Humphries P. and Walker K. (2003). Does flow modification cause geomorphological and ecological response in rivers? A literature review from an Australian perspective. Technical report 1/2004 CRC Freshwater Ecology, Canberra.

Maddock, I., Thoms, M., Jonson, K., Dyer, F. and Lintermans, M. (2004). Identifying the influence of channel morphology on physical habitat availability for native fish: application to the two-spined Blackfish (Gadopsis bispinosus) in the Cotter River, Australia. Marine and Freshwater Research 55: 173-184.

Marchant, R., and Hehir, G. (2002) The use of AUSRIVAS predictive models to assess the response of lotic macroinvertebrates to dams in south-east Australia. Freshwater Biology 47: 1033-1050.

Nelson, T.W. (2003). Fire intensity and benthic stream ecosystem responses to bushfire disturbance. Unpublished Honours thesis, University of Canberra.

Newson, M. (1994). Hydrology and the river environment. Clarendon Press, Oxford, 221 pp.

Norris R., Chester, H. and Thoms, M. (2004a). Ecological sustainability of modified environmental flows in the Cotter River during drought conditions, January 2003-April 2004. Unpublished report, CRC for Freshwater Ecology, 49pp.

Norris R., Liston P., Mugodo J., Nicols S., Quinn G., Cottingham P., Metzeling L., Perriss S., Robinson D., Tiller D. and Wilson G. (2004b). Multiple lines and levels of evidence for detecting ecological responses to management interventions. In: Proceedings of the Fourth Australian Stream Management Conference, Launceston, pp.

Osborne, W.S., Gillespie, G.R. and Kukolic, K. (1994). The spotted tree frog Litoria spenceri: an addition to the amphibian fauna of the Australian Capital Territory. Victorian Naturalist 111, 60-64.

Schofield N., Burt A. (2003). Issues in environmental water allocation - an Australian perspective. Water Science and Technology 48, pp. 83-88.

Scott, A. (2001). Water erosion in the Murray-Darling Basin: learning from the past. CSIRO Land and Water Technical Report No 43/01.

Walters C. J. and Holling C.S. (1990). Large-Scale management experiments and learning by doing. Ecology 71, pp. 2060-2068.

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Ward, J.V. (1992). Aquatic insect ecology v. 1. Biology and habitat. John Wiley & Sons Inc., New York.

Watson, C.C., Biedenharn, D.S. and Bledsoe, B.P. (2002). Use of incised channel evolution models in understanding rehabilitation alternatives. Journal of the American Water Resources Association 38: 151-160.

Welsh, H.H. Jr. and Ollivier, L. M. (1998). Stream amphibians as indicators of ecosystems stress: a case study from California's Redwoods. Ecological Applications 8: 1118-32.

Young, W. J., Ogden, R. W., Hughes, A. O. and Prosser, I. P. (2002) Predicting channel type from catchment and hydrologic variables. International Association of Hydrological Sciences 276, 53-60.

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Appendix A. Terms of Reference for reviewThe terms of reference for the review are: Provide advice on the appropriate approaches to determine the flows needed to

sustain aquatic ecosystems in the ACT (Environment ACT will specify some components we are particularly interested in, i.e. threatened fish, macroinvertebrates, frogs, crayfish). This advice should draw on local experience and relevant national information. This advice should recognise that the Environmental Flow Guidelines are being reviewed using current knowledge and data and there will not be an opportunity to collect further data during this process.

Provide advice on the actual flows needed to sustain aquatic ecosystems in the ACT. In the current guidelines we distinguish four types of aquatic ecosystems; natural, modified and created ecosystems, and those in water supply catchments. Different flow requirements are set for different catchments, reflecting the differing competing demands between resource use and protection. In order to assist the subsequent guideline review process in which ecological, social and economic values are considered, Environment ACT seeks advice on flows to be expressed as two scenarios;

o Flows that would ensure with a high degree of confidence that ecological values (including consideration of the requirements of threatened species where appropriate) of aquatic ecosystems are maintained

o Flows that would ensure with a moderate degree of confidence that ecological values of aquatic ecosystems are maintained

This advice may need to be in the form of flow requirements for specific reaches.

The advice will be about actual flows where data about the flows required for desired environmental outcomes exists, or a methodology for determining actual flows where the data are absent.

During periods of drought there may be temporary pressures to reduce environmental flows in water supply catchments to meet other water resource responsibilities. The CRCFE should provide advice on a flow regime that could sustain basic aquatic ecosystems processes (including consideration of the requirements of threatened species) without irreversible damage.

The current guidelines establish groundwater sustainable yields based partly on the need to protect stream baseflow. The CRCFE should provide advice on the importance of baseflows in ACT streams for maintenance of aquatic ecosystems, and the extent to which this flow component should be protected to maintain ecological values.

Current environmental flow guidelines specify “flow guidelines” for urban lakes and ponds in terms of a maximum drawdown. This requirement was included principally to protect macrophyte beds. The CRCFE should provide advice on the need for this component to protect ecological condition in lakes and ponds, and the form of any such requirement.

The CRCFE should provide advice on monitoring necessary to assess if the required ecological outcomes associated with environmental flow releases are achieved.

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The CRCFE should provide advice on opportunities for adaptive management of environmental flows

The CRCFE should provide advice on other ecological issues related to flow regimes as identified by the CRCFE.

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Appendix B. AUSRIVAS bands & their interpretation

Division of O/E taxa into bands or categories for reporting

The names of the bands refer to the relationship of the index value to the reference condition (band A). Under comments for each index, an explanation of the band is stated first, followed by possible interpretations.

Band Description O/E* taxa O/E* taxa interpretationsX More biologically

diverse than reference

O/E greater than 90th percentile of reference sites used to create the model.

More families found than expected. Potential biodiversity 'hot-spot' or mild organic enrichment. Continuous irrigation flow in a normally intermittent stream.

A Similar to reference

O/E within range of central 80% of reference sites used to create the model.

Expected number of families within the range found at 80% of the reference sites.

B Significantly impaired

O/E below 10th percentile of reference sites used to create the model. Same width as band A.

Fewer families than expected. Potential impact either on water and/or habitat quality resulting in a loss of families.

C Severely impaired

O/E below band B. Same width as band A.

Many fewer families than expected. Loss of families from substantial impairment of expected biota caused by water and/or habitat quality.

D Extremely impaired

O/E below band C down to zero. Few of the expected families and only the hardy, pollution tolerant families remain. Severe impairment.

*O/E is the ratio of taxa observed in the sample to the taxa expected to be in the sample based on the AUSRIVAS models.

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Appendix C. Leaf-green Tree Frog (Cotter River Form)The Cotter River Frog represents an unusual spotted form of the Leaf-green Tree Frog (Litoria nudidigitus) that occurs in the Cotter River. It is strikingly different to the widespread normal form (Osborne et al. 1994). It is now apparently confined to the Cotter River upstream of Bendora Dam (Osborne unpublished). The same colour form of the species has only been recorded on two other streams: the Goodradigbee River upstream of the cleared farming country (Hunter and Gillespie 1999) and the Gibbo River in north-eastern Victoria (G. Gillespie, Arthur Rylah Institute for Environmental Research, Melbourne, pers. comm.). The Cotter River population is of considerable regional significance, being in one of only two locations where the species occurs in the ACT. This frog is not a listed species of conservation significance, but due to its unique coloration it is an important component of the frog fauna of the ACT region (Lintermans and Osborne 2002).

The frog attaches its eggs to sticks and vegetation in pools and backwaters adjacent to the river. Substrates utilised by the tadpoles include rock, gravel, sand and rotting leaf litter (Hero and Gillespie 1993; Holloway 1997). Tadpoles generally use the still sections of streams, but are also found in a range of habitats including isolated and connected streamside pools, backwaters, and the main channel.

Semi-detached streamside pools (pools that are only connected to the main stream during peak flows) are important in-stream breeding sites for many species of frogs, including the Cotter River Frog. High stream flows during the warmer months (above natural frequencies) are likely to impact upon riverine frog populations because substantial rises in water level and velocity are likely to flush eggs and larvae downstream (Gillespie and Hines 1999; Gillespie and Hollis 1996). As well, inundated pools may be occupied by introduced trout, which are effective predators of the Cotter River Frog (Gillespie 2001).

When there is build-up of sediments, and colonisation of the stream channel by vegetation, reduce the availability of oviposition (egg-laying) sites and cover for larvae by blanketing the streambed and infilling of crevices between rocks, litter and cobble (Gillespie and Hines 1999; Gillespie 2001). Regular floods are important for maintaining these sheltering habitats; otherwise individuals are vulnerable to flushing effects from large flood events (e.g. Welsh and Ollivier 1998).

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Appendix D. MLLE - Applying MLLE to Cotter River environmental flows

Introduction

The Cotter River is an important ecological resource because of its high quality near-natural habitat and its populations of endangered and threatened fish species (Macquarie Perch, Two-spined blackfish and Trout Cod) and significant populations of native frogs, birds and mammals.

Severe drought in the ACT required the introduction of ‘drought flows’ in July 2003, which were based on absolute flow volumes of 20 ML/day and accompanying flushing flows approximately each two months. Also, implemented with this regime was variation of the low-flow volume from 10 to 30 ML/day, fortnightly, while maintaining the absolute volume. Additionally, bushfires throughout much of the Cotter River catchment confounded the impacts of the drought on water supply by degrading water quality and altering instream and catchment ecological processes.

The MLLE approach (see Fig. D1) could be used to determine if the ‘drought flows’ at least maintained the ecological condition of the Cotter River.

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Fig. D1. Summary of Multiple Lines and Levels of Evidence framework

9 - Inform conclusion

1 - Characteristics of human activity

8 - Additional lines of evidence

2 - Characteristics of impact location

3 - Question(s) & Conceptual model

4 - Relevant lines of evidence

5 - Literature review, Assemble and analyse local data

7 - Weight all literature and local data relative to quality


The following steps show how the MLLE approach may be used to determine whether the environmental flows guidelines (EFG) have maintained or improved ecological condition in the Cotter River.

1) Characteristics of human activity

The ‘human activities’ involved in the environmental flows guidelines are: reduction in the mean annual flow (MAF) reduction in frequency of all floods smaller than a 1:10 year event. reduction of baseflow variation in flow application of intermittent flushing flows.

2) Characteristics of impact location.

The Cotter River is a montane stream arising in the Scabby Range and flowing southwards along the eastern flank of the Brindabella Mountain range before diverting east and joining with the Murrumbidgee River. Most of the Cotter River catchment is rugged mountainous territory and thus has had little human disturbance and has good water quality (Hogg and Wicks 1989). Much of the native flora and fauna communities have suffered little disturbance in the upper catchment and represent a significant natural resource. The Cotter River has three dams along it to provide the Australian Capital Territory with potable drinking supplies. The uppermost Corin Dam is the main storage from which water is released to the Bendora storage before entering the reticulation system. Environmental flows are released from Bendora Dam. The Cotter storage is currently hardly used, and the water released for the environment from Bendora Dam flows freely through it. Most of Cotter River catchment was burnt by wildfire in January 2003, which altered much of the Cotter River and neighbouring catchments.

The modes of operations for the three dams differ. Corin Dam (the upper dam) releases water to the river channel to maintain water levels in Bendora Reservoir. Thus, the river downstream may have an altered flow regime but the annual volume may change little from natural. A gravity main supplies water from Bendora Dam (the middle dam) to the city of Canberra with little release to the river except for designated environmental flows to the river. Cotter Dam (the lower dam) has not been used for Canberra’s water supply for around 30 years, and often overtops. The lower Cotter sub-catchment has less restricted land use and public access compared to the upstream dams. Recently, environmental flows were introduced to the system (http://www.environment.act.gov.au/files/environmentalflowguidelines.pdf).

It could be expected that Corin Dam would have little effect on the Cotter River ecosystem because the annual volume of water released to river channel should be similar to the pre-regulation volume. However, the change of flow regime may have had direct or indirect effects through changes to temperature and disturbance regimes or nutrient concentrations. Potentially, Bendora Dam could have the most effect because of water abstraction and consequent reduction in water released to the river. However, environmental flows (if effective) should ameliorate these effects. Cotter Dam, essentially operating like a large weir, may be expected to have the least

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http://www.environment.act.gov.au/files/environmentalflowguidelines.pdf


ecological effect but might still display some detrimental effects resulting from reduced water flows caused by the operation of Bendora Dam and sediment trapping. Therefore, the ecological question, and MLLE application, should focus on biological changes below the Bendora Dam.

3) Question(s) & Conceptual model

The question to address using the MLLE approach: Did a change in environmental flow releases to the Cotter River below Bendora Dam from July 2003 to 2004 result in a deterioration of the aquatic ecosystem in the short term (<2 years).

The conceptual model: A conceptual model will be developed to identify the possible biological effects of the EFG. The information in the conceptual model will help determine relevance of studies when reviewing the literature. The conceptual model should be of a ‘pristine’ ecosystem, so that the effects of the change of interest can be traced. The following steps are used in the development of a conceptual model:

a) List the important system descriptors, e.g. Cotter River is an upland river (700-900m) with many tributaries; in SE Australia; high aseasonal rainfall (1000mm); steep vegetated catchment; substrate is predominantly cobble, boulder and bedrock; the impounded part of the catchment is a national park and has native vegetation.

b) List and describe the important components in the ecosystem: Important geomorphological components, Major biological components, Major processes operating and the relative importance of different pathways.

c) Describe the human activity or agent as precisely as possible and identify its relationship to other components or processes in the conceptual model. Where multiple agents are potentially contributing to an effect, the aim is to identify the dominant stressor; that which makes the largest contribution. This step enables identification of appropriate lines of evidence.

d) List the candidate lines-of-evidence, e.g. fewer invertebrate taxa than expected; change in periphyton abundance.

e) Define the scope of the investigation and document temporal and spatial issues. For example:

The scope of the study needs to be limited (e.g. does a particular stressor cause biological impairment?). MLLE should not consider broad issues (i.e. multiple stressors) unless they can be considered as a single scenario.

Consider temporal issues such as season. Will studies conducted in one season provide adequate evidence or do you need to consider only studies conducted over two or more seasons?

If there is interest in a population-change response then consider generation times.

Is there interest in the effects of a fire after 1 week or 10 years? At what distance downstream of the dam is a response expected?

f) The operational question can now be articulated better to identify:

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a 'quantifiable' causal agent the 'quantifiable' effects the appropriate resolution for the lines-of-evidence. For example, the biota

may respond at a species-level rather than family level.

See Fig. D2 for a graphical representation of the conceptual model of the Cotter River below Bendora Dam.

4) Relevant lines of evidence

The relevant lines of evidence are drawn from the conceptual model. As shown in Fig D2 the relevant lines of evidence can be updated if new lines are found in the literature.

5) Collecting the evidence

Once the question and the relevant lines of evidence have been defined the evidence for the causal link between the human activity and the ecological condition of the Cotter and similar rivers is collected. The evidence is collected from journal articles and local data (which includes grey literature).

6) Additional lines of evidence

Additional lines of evidence identified from the evidence collection phase are incorporated into the conceptual model.

7) Weight all literature and local data relative to quality

In cataloguing each line of evidence (LOE), record the number and the importance of studies against the different levels of evidence. The levels of evidence used are adapted from Downes et al. (2002) and include:

‘biological plausibility’ — absorbed into the conceptual model to indicate ecologically relevant LOEs, rather than kept as a line of evidence itself

‘presence of a biological response’ — a recasting of the ‘experimental evidence’ level but including evidence from all types of study including experimental and observational studies

‘evidence of a dose response relationship with the stressor’ ‘consistency of association’ — consistent spatial and temporal association of

stressor and biological response.

Our MLLE approach has a formal procedure for weighting the quality of papers or the of the study design in the Cotter River flows project based on the three study quality attributes; type of study design, the number of control/reference locations and the number of impact locations (Table D1). Studies in which error terms are well controlled (e.g. BACI designs) should exert greater influence than less rigorously controlled designs (e.g. only impact sites sampled). Having a control or reference brings an improvement in inferential power. There is some increase in inferential power from having more than one control. A larger number of control locations adds

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weight because it better estimates the envelope of ‘normal’ location behaviour (Downes et al., 2002) so that departure from ‘normal’ can be detected with more confidence. More impact locations leads to a better estimate of the range of ecological outcomes and stronger comparisons with control/reference conditions with which they are compared.

An overall study (quality) weight is derived by summing the weights of each of the three study quality attributes. The overall study weights are then converted into study quality categories (Table D2) with the advantage that they more immediately relay the importance of the study than a numerical value. From Table D2, high quality studies have a median weight or 7.5 (i.e. (5+10)/2) and low quality studies have a median weight of 2.5 (i.e. (1+4)/2). A line of evidence with a combination of high and low quality studies with a median study weight of 20 or more has a high level of evidence for the ‘biological response’ and ‘dose response’ causal criteria (Table D3). A line of evidence with a combination of high and low quality studies with a median study weight of less than 20 has a low level of evidence for the ‘biological response’ and ‘dose response’ causal criteria (Table D3). The converse is true for the ‘consistency of association’ (Table D3).

The possible outcomes for a given line of evidence are show in Table D4. They show the whether the evidence according to the causal criteria leads to enough support for causal relationship between the line of evidence and a given human activity or whether there is either no support or insufficient evidence for causal relationship.

The MLLE approach can be used to determine if new environmental flows guidelines will also be successful.

Table D1. Weights applied to study types and control/reference and impact locations

Study design type WeightAfter impact only 1Reference/Control vs impact no before 2Before vs after no reference/control 2Gradient response model 3BACI or BARI MBACI or Beyond MBACI 4Number of reference/control sites0 01 2> 2 3Number of impact locations1 02 2> 2 3

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Table D2. Scheme for categorizing the importance of studies

Overall study weight Study importance category5–10 High1–4 Low

Table D3. Biological response and dose response weighting by study quality. Consistency of association?Number of Low quality studies showing support

condition Number of High quality studies showing support

Sum of the Median Quantitative study weights

Conclusion – evidence for causal criterion

Biological response and dose response> 0 AND > 2 3 x 7.5 = 22.5 High> 2 AND 2 (2 x 2.5) + (2 x 7.5) = 20 High> 5 AND 1 (5 x 2.5) + 7.5 = 20 High> 8 AND > 0 8 x 2.5 = 20 High< 5 AND 1 (4 x 2.5) + 7.5 = 17.5 Low< 2 AND 2 (1 x 2.5) + (2 x 7.5) =

17.5Low

< 8 AND 0 7 x 2.5 = 17.5 Low

Consistency<2 AND 2 High <5 AND 1 High <8 AND 0 High >= 0 AND >2 Low >=2 AND 2 Low >=5 AND 1 Low >=8 AND >= 0 Low

Table D4. Possible outcomes after combining outcomes from assessing various study typesOutcomes Biological response Dose response Inconsistency ConclusionOutcome 1 H L L Support for hypothesisOutcome 1 L H L Support for hypothesisOutcome 2 L L L Insufficient evidenceOutcome 3 L L H Support for counter

hypothesis

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Fig. D2. Conceptual Model, Cotter River below Bendora Dam.

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Conceptual model - Cotter River below Bendora Dam

Reduced flow

Riparian vegetation encroaches into the channel and reduces channel capacity. Unpalatable filamentous algae accumulates. Reduced flow results in armouring, reduced flushing of detritus, nutrients, fine sediment. Habitat space for macroinvertebrates and fish in the substratum is reduced because of armouring and infilling with fine sediments. Also, some parts of the bottom may be exposed. Sediment and organic matter may enter the channel directly from adjacent valley slopes and may not be flushed with low flows in the main channel. Water quality dependant on releases from Bendora Dam (Canberra’s water supply) – further downstream water quality (and quantity) also influenced by tributary and groundwater input.

1

3

2

4

P < R

5

1 2

3 4

5

Natural low flow

6

6

Upland, rocky stream with low EC and nutrient content.

Bendora Dam is at 700 m ASL

Environment flows released to the river from Bendora Dam

Conceptual model - Cotter River below Bendora Dam

Reduced flow

Riparian vegetation encroaches into the channel and reduces channel capacity. Unpalatable filamentous algae accumulates. Reduced flow results in armouring, reduced flushing of detritus, nutrients, fine sediment. Habitat space for macroinvertebrates and fish in the substratum is reduced because of armouring and infilling with fine sediments. Also, some parts of the bottom may be exposed. Sediment and organic matter may enter the channel directly from adjacent valley slopes and may not be flushed with low flows in the main channel. Water quality dependant on releases from Bendora Dam (Canberra’s water supply) – further downstream water quality (and quantity) also influenced by tributary and groundwater input.

1

3

2

4

P < R

55

1 2

3 4

5

Natural low flow

6

6

Upland, rocky stream with low EC and nutrient content.

Bendora Dam is at 700 m ASL

Environment flows released to the river from Bendora Dam


Fig. D3. Conceptual model of fire effects in the Cotter River

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Ash, charcoal Ash, charcoal and soil input and soil input increasesincreasesnutrient loadnutrient load

More light exposureMore light exposure

Temperature Temperature and turbidity and turbidity increaseincrease

Filamentous algae Filamentous algae growthgrowth

Streambed habitat supports Streambed habitat supports diverse aquatic algae, plants diverse aquatic algae, plants and animalsand animals

Low nutrient Low nutrient inputsinputs

Stream bed habitat Stream bed habitat smothered and scouredsmothered and scoured

BURNTBURNTUNBURNTUNBURNT

Template shapes developed by SEQRWQMS (2001)

Ash, charcoal Ash, charcoal and soil input and soil input increasesincreasesnutrient loadnutrient load

More light exposureMore light exposure

Temperature Temperature and turbidity and turbidity increaseincrease

Filamentous algae Filamentous algae growthgrowth

Streambed habitat supports Streambed habitat supports diverse aquatic algae, plants diverse aquatic algae, plants and animalsand animals

Low nutrient Low nutrient inputsinputs

Stream bed habitat Stream bed habitat smothered and scouredsmothered and scoured

BURNTBURNTUNBURNTUNBURNT

Template shapes developed by SEQRWQMS (2001)


Fig. D4. Longitudinal conceptual model of the Cotter River

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Long pools form upstream of short channel constrictions formed by bedrock bars or local gravel deposits that act as riffle areas. Riffle areas have relatively high energy that transport fine sediment and other material from upstream or from pool areas. Fine sediment accumulates in pools. Lateral connection to the floodplain (usually less than 30m wide) is restricted by the valley morphology. Detritus and nutrients are added to the stream by the surrounding catchment, most of which are transported downstream when flows are higher.

1

3

2

4

1

2

43

3

5

5

Pool-riffle system

5

5

Long pools form upstream of short channel constrictions formed by bedrock bars or local gravel deposits that act as riffle areas. Riffle areas have relatively high energy that transport fine sediment and other material from upstream or from pool areas. Fine sediment accumulates in pools. Lateral connection to the floodplain (usually less than 30m wide) is restricted by the valley morphology. Detritus and nutrients are added to the stream by the surrounding catchment, most of which are transported downstream when flows are higher.

1

3

2

4

1

2

43

3

5

5

Pool-riffle system

5

5

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