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 Ogden

Peter Davies

Bronwyn Rennie

James Mugodo

Peter Cottingham

This report has been prepared by:

Ralph Ogden[1], Peter Davies[2], Bronwyn Rennie[1], James Mugodo[1], and Peter Cottingham[1].

1. CRC for Freshwater Ecology

2. Freshwater Systems

Acknowledgments

This 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)

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:

Web:

A review of the ACT Environmental Flows Guidelines (1999)

Executive summary

1. Review

1.1 Scope

1.2 Approach

2. The 1999 Guidelines and related documents

2.1 Origin of environmental values, objectives and e-flow policies

2.2 The 1999 Environmental Flow Guidelines

3. New knowledge

3.1 Monitoring activities

3.2 R&D activities

3.3 Main messages for e-flow management

4. Advice on appropriate approaches

4.1 Context for e-flow management

4.2 Context of this review

4.3 Use of Ecological Objectives

4.4 Linking objectives to the flow regime

4.5 Monitoring & adaptive management

4.6 Linking e-flows restorations to refuge habitats

5. Existing flow extraction and e-flow components

5.1 Low flows

5.2 Flushing flows

5.3 Flows in drought

5.4 Special purpose flows

5.5 Maximum diversion limits

5.6 Groundwater extraction

5.7 Drawdowns in urban lakes

5.8 Responses to fire

6. Potential new objectives and e-flows

6.1 Draft values & objectives identified at workshop

6.2 Science underpinning draft objectives

6.3 Other potential objectives

6.4. Flow regime needed to satisfy objectives

7. Advice on monitoring & adaptive management

7.1 Monitoring program

7.2 Adaptive management

8. References

Appendix A. Terms of Reference for review

Appendix B. AUSRIVAS bands & their interpretation

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

Appendix C. Leaf-green Tree Frog (Cotter River Form)

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

Introduction

1) Characteristics of human activity

2) Characteristics of impact location.

3) Question(s) & Conceptual model

4) Relevant lines of evidence

5) Collecting the evidence

6) Additional lines of evidence

7) Weight all literature and local data relative to quality

Executive summary

Background

1) 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 guidelines

3) 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 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.

1. Review

1.1 Scope

A 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.

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.

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:
  3. 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.
  4. identify the individual flow regime components required to achieve the objectives, and make general suggestions for improving the EFG.
  5. 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.
  6. 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.

2. The 1999 Guidelines and related documents

2.1 Origin of environmental values, objectives and e-flow policies

The 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 Actmust 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 Actobjectives (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.

Table 1. Performance objectives, indicators and criteria. Source: Licence No.WU67

Period / 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 fish
Establishment 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 Guidelines

The 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.

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.

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.