HUME AND DARTMOUTH DAMS OPERATIONS REVIEW REFERENCE PANEL Hume and Dartmouth Dams Operations Review Options Paper N O V E M B E R 1 9 9 8 HUME AND DARTMOUTH DAMS OPERATIONS REVIEW REFERENCE PANEL Hume and Dartmouth Dams Operations Review Options Paper N O V E M B E R 1 9 9 8 Please note! The deadline for comment on this paper is Wednesday 10 February 1999 For details see page 1 (‘About this Options Paper’) i HUME AND DARTMOUTH DAMS OPERATIONS REVIEW REFERENCE PANEL Published by: Hume and Dartmouth Dams Operations Review Reference Panel Postal address: c/- MDBC, GPO Box 409, Canberra ACT 2601 Office location: c/- Murray-Darling Basin Commission, 2nd Floor, 7 Moore Street, Canberra City, Australian Capital Territory Telephone: (02) 6279 0100; international + 61 2 6279 0100 Facsimile: (02) 6248 8053; international + 61 2 6248 8053 E-mail: [email protected] Website: http://www.mdbc.gov.au Map on cover: © Copyright Commonwealth of Australia 1985 Remainder of publication: © Copyright Murray-Darling Basin Commission 1998 This document may be reproduced in whole or in part, provided that the information in it is not sold for commercial benefit and its source is acknowledged. Dissemination and discussion of the document is encouraged. For further copies and assistance contact the Reference Panel at the above address. ISBN 1 875 209 92 1 ii HUME AND DARTMOUTH DAMS OPERATIONS REVIEW Contents 1. About this options paper 3 2. Overview 5 3. Introduction 7 3.1 History of River Murray water regulation 7 3.2 Roles of Hume and Dartmouth storages 7 3.3 The Operations Review 8 3.4 Work related to the review 8 3.5 Community consultation 9 4. Water regulation issues 11 4.1 Identification of issues 11 4.2 Issues that do not involve competing claims for water 11 4.3 Issues that involve competing claims for water 12 5. Issues that do not involve competing claims for water 13 5.1 Economic impact of Dartmouth Dam on the Mitta Mitta valley 13 5.1.1 Effect of Dartmouth Dam on pasture productivity 13 5.1.2 Flood duration in the Mitta Mitta valley 14 5.1.3 Adverse effects on agricultural land at peak regulated flow 16 5.1.4 Erosion on the Mitta Mitta River 16 5.2 Economic impact of Hume Dam on the floodplain below 17 5.2.1 Adverse effects on agricultural land at peak regulated flow 17 5.2.2 The need for a comprehensive river management plan between Hume and Yarrawonga 17 5.3 Effect of dams on non-flow environmental values 19 5.3.1 Impact of Dartmouth Dam on water temperature and quality 19 5.3.2 Effects of regulated flows and rain rejections on natural drying cycles in wetlands 20 5.4 The need to better manage minimum flows downstream of Mildura 21 5.5 The need for improved communication 21 1 HUME AND DARTMOUTH DAMS OPERATIONS REVIEW REFERENCE PANEL 6. Issues that involve competing claims for water 23 6.1 Issues and approaches to solving them 23 6.2 Testing single operational changes 24 6.2.1 Natural conditions 26 6.2.2 Benchmark (B42800) 26 6.2.3 Fill and spill (B42810) 26 6.2.4 Provision of airspace (B46770) 27 6.2.5 Relaxed pre-release rules (B42840) 27 6.2.6 Translucent flows (B46750) 28 6.2.7 Use of Dartmouth power station during floods (B42801) 28 6.2.8 “Sharing the Murray” proposal for the Barmah-Millewa forest (B47850) 29 6.2.9 Increased pre-release from Hume Dam (B46160) 30 6.3 Scenarios outside the scope of the review 32 6.4 Combined scenarios 33 7. Summary of options and preliminary panel views 37 Appendix A: Terms of reference for the Operations Review 41 Appendix B: Reference panel 43 Appendix C: Key issues identified in scoping study 45 Appendix D: Details of “Backgrounder” papers 47 Appendix E: Issue register 49 Appendix F: Supporting documents and references 51 Glossary 53 2 HUME AND DARTMOUTH DAMS OPERATIONS REVIEW 1. About this options paper In December 1996 the Murray-Darling modelling group has carried out the necessary computer simulations. Basin Ministerial Council agreed that This options paper is the result of the review to November 1998. It describes the issues that have been the way in which Hume and identified as needing attention, the way in which the Dartmouth dams are operated should panel has gone about its task, the tensions that arise because of competing objectives for managing the be reviewed. regulated Murray, and possible improvements and changes to the balance between competing objectives. he review has been guided by a reference panel At this stage the panel has reached no fixed Tconsisting of members representing different conclusions. The paper presents options, and in most interest groups and drawn from the general cases also presents a preliminary panel view. community, and supported by relevant government The work to date now needs to be exposed to the agencies. wider community. The Murray-Darling Basin Commission appointed A series of public meetings will be held to present the reference panel, and the panel’s final product will and explain the material in the paper, discuss the be a report and recommendations to the Commission. options, and stimulate comment and feedback. The However the panel is fully independent and its work panel expects to refine its views in the light of public has not been influenced or directed by the comment before making its recommendations to Commission, nor has the Commission considered or the Commission. endorsed this options paper. Comments may be made to any member of the The technical work has been managed by a small panel (see contact numbers in appendix B) or can be project team. The team has utilised private addressed to Clarke Ballard, c/o Murray-Darling Basin consultants, expertise available in government Commission, GPO Box 409, Canberra ACT 2601; agencies and the internal resources of the Murray- telephone 02 6279 0176; fax 02 6230 6005; Darling Basin Commission. The Commission’s email: [email protected] The deadline for comment is 10 February 1999. HUME AND DARTMOUTH DAMS OPERATIONS REVIEW 3 2. Overview The terms of reference of the review (see — for example, the fact that water temperatures are lowered and steady regulated flows diminish appendix A) are essentially to review the riverbank vegetation and can aggravate erosion. operating procedures for the Hume and The panel has been able to arrive at preliminary views on most of these issues, which tend to be reasonably Dartmouth Dams and to recommend self-contained. how they might be amended to better The second group of issues essentially revolves around trade-offs between different management address the competing objectives of water objectives, and judging where the balance between them should lie. Computer models were used supply, environmental enhancement and extensively to analyse different possible operational scenarios. These led the panel to a fairly clear flood mitigation. A broad perspective is understanding of the effects of each strategy and those required, including consideration of a strategies — or packages of strategies — that might be useful in achieving a different balance. However, no wide range of economic, social and option was found that resulted in improvements from the viewpoint of every interest group. environmental factors. The panel has therefore been unable, so far, to reach a definitive view on strategies that should be he reference panel visited many areas of interest recommended. Despite this, it has formed a view that Talong the river, and spent a lot of time collecting the likely direction is towards a package that includes: input from interested groups. The result was a long list • arrangements for effectively watering the Barmah- of issues that were seen as important by one or more Millewa forest using the water already allocated for interest group. It was necessary to be rigorous in that purpose, pursuing only those issues that are related to dam • continued “harmony” operation of Hume and operation. Dartmouth storages, Another difficulty in maintaining focus has been the • some form of varied pre-release strategy to mimic other processes, programs and inquiries (such as the natural variability in flows below the storages, and Snowy Inquiry and work on environmental flows) that • possibly the acquisition of easements over are under way at present. It has been necessary to frequently flooded land between Hume and minimise potential duplication and overlap by forming, Yarrawonga. as clearly as possible, a picture of the boundaries between the various activities and where the review fits Such a package could be implemented with minor into the larger picture. environmental benefits and little adverse effect on The panel has found that issues fall into two distinct consumptive users, beyond that already in train because groups: those that do not involve finding a balance of the water already committed to Barmah-Millewa between competing claims to water, and those that do. watering. However, there would be further environmental The first group of issues includes: benefits, and further adverse effects on consumptive use, • the need for better communication between the if pre-release targets were revised to introduce a higher- Commission’s operational arm and interested than-current risk of storages failing to fill. community groups; Floodplain dwellers would obtain some benefit from • economic impacts of the dams on human uses of these strategies, but those benefits would not the floodplains below them; necessarily increase as the specified risk of storages • management of flow variability in the river failing to fill was increased. downstream; and The panel seeks opinions from the wider • environmental impacts of the dams (excluding the community on where the balance between the various impacts of extraction of water further downstream) competing interests should lie.