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River Murray systemannual operating planEnd October 2015 update

2015–16 Water Year1 June 2015–31 May 2016

River Murray system annual operating plan End October 2015 update

Published by the Murray‒Darling Basin Authority

Postal Address: GPO Box 1801, Canberra ACT 2601Telephone: (02) 6279 0100 international + 61 2 6279 0100Facsimile: (02) 6248 8053 international + 61 2 6248 8053Email: [email protected]: http://www.mdba.gov.au

MDBA publication no.: 22/15ISBN (online): 978-1-925221-42-8

All material and work produced by the Murray‒Darling Basin Authority constitutes Commonwealth copyright. MDBA reserves the right to set out the terms and conditions for the use of such material.

With the exception of the Commonwealth Coat of Arms, photographs, the Murray‒Darling Basin Authority logo or other logos and emblems, any material protected by a trade mark, any content provided by third parties, and where otherwise noted, all material presented in this publication is provided under a Creative Commons Attribution 3.0 Australia licence.

http://creativecommons.org/licenses/by/3.0/au© Murray‒Darling Basin Authority 2015.

The Murray‒Darling Basin Authority’s preference is that you attribute this publication (and any Murray‒Darling Basin Authority material sourced from it) using the following wording within your work:

Title: River Murray system annual operating plan End October 2015 updateSource: Licensed from the Murray‒Darling Basin Authority under a Creative Commons Attribution 3.0 Australia Licence

As far as practicable, material for which the copyright is owned by a third party will be clearly labelled. The Murray‒Darling Basin Authority has made all reasonable efforts to ensure that this material has been reproduced in this publication with the full consent of the copyright owners.

Inquiries regarding the licence and any use of this publication are welcome by contacting the Murray‒Darling Basin Authority.

Cover image: Lake Mulwala during the scheduled drawdown in winter 2015. Photograph by Peter McLean. Copied with the permission of Yarrawonga Flight Training.

DisclaimerTo the extent permitted by law, the Murray‒Darling Basin Authority and the Commonwealth excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this report (in part or in whole) and any information or material contained within it.

AccessibilityThe MDBA makes its documents and information available in accessible formats. On some occasions the highly technical nature of the document means that we cannot make some sections fully accessible. If you encounter accessibility problems or the document is in a format that you cannot access, please contact us.

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IntroductionThe River Murray system annual operating plan (operating plan) for the 2015–16 water year (1 June 2015 to 31 May 2016) was released in August 2015. The operating plan provided the context and descriptions of how the River Murray system may have been operated under a range of assumed scenarios.

This document provides an update of scenarios, as at end October 2015, and should be used in conjunction with the original plan. The scenarios have been prepared by the Murray–Darling Basin Authority (MDBA) with input from the Australian Government and the states of New South Wales, Victoria and South Australia through MDBA's Water Liaison Working Group. This operating plan may be updated again later this water year if significant changes are required. The states will also receive regular updates through the Water Liaison Working Group as the season progresses.

Current conditionsRiver Murray system inflows in the first five months of this water year have remained well below average in each month (Table 1, Figure 1). Murray system inflows (excluding Darling and Snowy inflows, environmental inflows from tributaries and inter-valley trade) in this period have totalled approximately 2,070 GL (91% Annual Exceedance Probability or AEP) compared with the long-term average for this period of 6,500 GL and median of 5,310 GL. These low inflows are the result of rainfall which has been average to very much below average in the Snowy Mountains and Victorian Alps (Figure 2), a relative lack of large rainfall events and high temperatures in September and October.

Table 1: Monthly inflows (GL) and annual exceedance probabilities (AEP) to the River Murray system from June to October 2015.

Month Hume unregulated inflow

Murray system inflow* (excluding Darling)

Murray system inflow* (including Darling)

June 82 GL (72% AEP) 237 GL (81% AEP) 249 GL (80% AEP)July 153 GL (64% AEP) 429 GL (80% AEP) 448 GL (81% AEP)August 243 GL (66% AEP) 670 GL (78% AEP) 685 GL (79% AEP)September 167 GL (89% AEP) 486 GL (90% AEP) 496 GL (90% AEP)October 83 GL (95% AEP) 245 GL (95% AEP) 250 GL (95% AEP)

*excluding Snowy inflows, environmental inflows from tributaries and inter-valley trade.

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http://www.mdba.gov.au/media-pubs/publications/river-murray-system-aop-2015-16


0

20,000

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80,000

Flow

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Long term average

2015-16

2014-15

Figure 1: Murray system daily inflows (excluding Snowy, Darling, inter-valley trade and environmental inflows).

Figure 2: Monthly rainfall deciles in the Murray–Darling Basin for June to October 2015 (Source: adapted from Bureau of Meteorology).

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Update on operations Maintenance and construction

Lake Mulwala was raised back to its normal operating range of 124.6–124.9 m AHD in late July following a lowering for structural works and management of the aquatic weed Egeria densa.

The weir pool at Mildura was returned to full supply level in early August after major maintenance and repairs to the trestles and trestleway. The lock was re-opened in September after refurbishment.

Mullaroo regulator was completed in July 2015, enabling the regulation of flows into Mullaroo Creek and the lower Lindsay River.

Refurbishment of Lock 15 at Euston is scheduled to commence in late January 2016 following the Australia Day weekend. The lock will be closed to boat traffic for approximately four months. Further information will be provided in a media release when dates are confirmed.

Weir pool variations

Variations in the levels of weir pools at Euston and at Locks 7, 8 and 9 are continuing as planned. Over summer, the weir pool at Euston will be close to full supply level, with lowering below full supply level expected to commence in March. At Locks 7, 8, and 9, the weir pool levels are planned to be drawn below their full supply level over summer and are expected to return to normal full supply level by May 2016. Further information is provided in the media release available on the MDBA website.

In South Australia, the weir pool at Lock 2 has been raised up to 50 cm above its normal pool level in October and at Lock 5 the weir pool has been raised up to 45 cm. These weir pool levels will be returned to their full supply level by December. Further information is available on the SA Department of Environment, Water and Natural Resources website.

In addition to the variations in weir pool levels outlined above, the weir pools at Yarrawonga, Torrumbarry, Euston, and Mildura may need to be drawn down for periods of up to two weeks to meet any peak water demands if extremely hot, dry conditions occur.

Consumptive demands

River Murray System diversions from 1 June 2015 to 31 October 2015 (not including Hume environmental water releases) for NSW and Victoria have totalled approximately 590 GL. This is significantly less than June to October 2014, when diversions totalled approximately 900 GL.

The reduced diversions to date in 2015-16 reflect the relatively low water allocations arising from poor inflows so far this water year. In NSW, Murray high security and general security allocations as of early November 2015 were 97% and 13% respectively, compared with 97% and 39% at the same time last year. In Victoria, Murray high reliability and low reliability allocations as of early November 2015 were 85% and 0% respectively, compared with 100% and 0% at the same time last year.

South Australian high security allocations as of early November 2015 are 100%, which is the same as this time last year.

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Environmental water

Approximately 430 GL of environmental water has been released from Hume Reservoir from late June until late October. The bulk of this water was carried over from the previous season for such a watering. The water was used to boost flows to better reflect natural flow regimes and, since late July, has contributed to overbank flows into the Barmah-Millewa Forest. These overbank flows are planned to recede during early November, although some watering of targeted wetlands is planned to continue to support bird breeding events.

Environmental water reaching the River Murray from the Goulburn system for the period from June 2015 to end May 2016 is now expected to be 230–330 GL. This volume includes water already delivered as higher base flows since early June and a spring “fresh” (a short period of within-channel higher flow) in October. Higher base flows in the Goulburn River are expected to continue for the remainder of the water year, using both environmental water and inter-valley transfers, with the possibility of a fresh in late February–March 2016.

Small scale environmental watering events have been undertaken throughout spring in Gunbower Creek, Gunbower Forest, Hattah Lakes and Lake Wallawalla. Each of these events is due for completion by mid-December.

No environmental water is currently expected to reach the River Murray from the Murrumbidgee River in 2015–16.

South Australia operations

There has been no unregulated flow into South Australia during the water year to date. Approximately 548 GL of environmental water has been delivered to South Australia from June to October 2015, in addition to full entitlement flows. South Australia currently has 103 GL of deferred entitlement flow in MDBA controlled storages. This water has been stored under South Australia’s storage right (Schedule G of the Water Act 2007). Plans are in place to increase this volume over the coming months in response to the ongoing dry conditions. This deferred water will help to meet critical human water needs and private carry-over in future years.

The Chowilla floodplain works have been used again this year to provide higher flows through Chowilla Creek, via Slaneys and Pipeclay Creeks. This further testing of the Chowilla works is expected to be complete by mid-December.

Releases through the barrages at the Lower Lakes are continuing as at 31 October. However, releases may be limited in the coming months to help safeguard Lower Lake levels in 2015–16 should dry conditions persist.

Operating scenarios as of end October 2015The actual conditions that occur during the remainder of the 2015–16 water year will inevitably be different to the scenarios in this updated plan, and therefore river operations will also be different to any projection presented. Nevertheless, these scenarios should provide a useful indication of potential river operations for the remainder of 2015–16 water year.

River Murray System inflows to date in 2015–16 have been tracking close to a 95% AEP scenario. In the original operating plan, the figures presented an extreme dry scenario

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(approximately 100% AEP) and a dry scenario (approximately 90% AEP). There is a significant difference in inflows between these two scenarios, and therefore MDBA has included a ‘very dry’ scenario (approximately 95% AEP) in this end October update of the operating plan. The very wet scenario included in the original operating plan has not been updated as Bureau of Meteorology streamflow outlooks indicate that such high inflows would be unlikely over the remainder of the season. If the current dry conditions persist, flows and storage volumes are most likely to follow the trends of the dry and very dry scenarios.

This updated operating plan assumes there will be modest environmental flows (80–150 GL) across the South Australian border from November onwards in most scenarios. Environmental water delivery to South Australia in summer and autumn 2016 may be increased if additional water is made available by environmental water holders and the delivery is operationally feasible. This situation is depicted in the dry scenario, which assumes 280 GL environmental water delivery across the South Australian border from November onwards.

At Lake Victoria, a storage volume of less than 350 GL may be targeted at the end of May 2016 in the drier scenarios, subject to approval by Ministerial Council. This measure aims to increase the chance of improved water availability in 2016–17 if very dry conditions continue.

Low releases from the Menindee Lakes have been assumed in all the dry scenarios of this revision. Since 8 September 2014, the flow at Weir 32 has been held below the normal minimum flow by Water NSW to conserve water in the lakes. Consequently, inflow to the River Murray from the lower Darling River has been assumed to be negligible in these dry scenarios. In the near average scenario, moderate inflows into the Menindee Lakes have been assumed and consequently the release at Weir 32 could be returned to the minimum flow by NSW DPI Water and Water NSW. In the wet scenario, the volumes in the Menindee Lakes may be sufficient to enable the MDBA to call on water as part of normal River Murray system operations.

This update contains two sets of figures for each structure/site.

• The first set contains the same information as forecast in the original operating plan and illustrates how river flows (as monthly averages) and storage levels (at the end of each month) have tracked against the original outlooks, for example Figure 3.

• The second set shows an updated operating plan as of 31 October 2015 and illustrates what the river flow and storage levels are now forecast to be over the remainder of the 2015–16 water year, for example Figure 4.

It should be noted that environmental and consumptive water use assumptions vary significantly between each of the scenarios. These assumptions influence operations of the system in each of the different scenarios.

Barmah Choke trade

Standard policy prohibits the net trade of allocations from above the Barmah Choke to downstream to protect the delivery of downstream water entitlements. Without the trade restriction, a potentially large volume of trade water, in addition to the normal downstream demand, is likely to exceed the limited channel capacity through the Barmah Choke.

The default policy therefore means that trade downstream of the Choke may only occur when there has been sufficient matching trade in the opposite direction i.e. no net trade downstream.

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MDBA is responsible for keeping track of this balance of trade and at the time of preparation of this update there was significant capacity for trade to occur from upstream to downstream.

MDBA has only relaxed this trade restriction in the past when there was a low risk of affecting the delivery of water to meet the normal downstream demand. MDBA regularly considers the system outlook and undertakes assessments described in the Annual Operating Plan to see if there is scope to relax the trade restriction.

Each scenario considers the key drivers of water delivery through the choke including:

current storage levels potential future inflows, demands and system losses the availability of water downstream of the Choke including in Menindee Lakes and from

IVT calls from the Murrumbidgee and Goulburn Valleys end of season reserve requirements in Lake Victoria.

This Annual Operating Plan update shows that for a wide range of scenarios over the remainder of this season, channel capacity through the Barmah Choke (around 10,000 ML/day downstream of Yarrawonga Weir) would be reached, or nearly reached, for prolonged periods to deliver required flows. The MDBA and the WLWG will continue to monitor conditions which could influence decisions around the Choke trade restriction.

Further information on the trade rule and the latest information on the current capacity to trade across the choke can be found on the MDBA website. Interestingly, since the normal trade restriction was reinstated in October 2014, these has been net trade upstream, which has meant that over the past 13 months, with the exception of the first week of restriction, limited downstream trade has been available at all times.

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http://www.mdba.gov.au/river-data/barmah-choke


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Jun-15 Jul-15 Aug-15 Sep-15 Oct-15 Nov-15 Dec-15 Jan-16 Feb-16 Mar-16 Apr-16 May-16

Stor

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Extreme dry scenario Dry scenario Moderate scenario Near average scenario

Wet scenario Very wet scenario Nominal Generation Limit (432 m) Capacity

Last season 2015-16

INDICATIVE FORECAST ONLY: SUBJECT TO REVISION AS CONDITIONS CHANGE

Figure 3: Original Dartmouth Reservoir storage outlook.

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Figure 4: End October Dartmouth Reservoir storage outlook.

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Figure 5: Original Dartmouth Reservoir release outlook.

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Figure 6: End October Dartmouth Reservoir release outlook.

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Very wet scenario Capacity (3005 GL) Last season 2015-16


Figure 7: Original Hume Reservoir storage outlook.

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Figure 8: End October Hume Reservoir storage outlook.

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Figure 9: Original Hume Reservoir release outlook — flow at Doctors Point.

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Figure 10: End October Hume Reservoir release outlook — flow at Doctors Point.

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Figure 11: Original Yarrawonga Weir release outlook.

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Figure 12: End October Yarrawonga Weir release outlook.

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Figure 13: Original Euston Weir flow outlook.

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Figure 14: End October Euston Weir flow outlook (note: vertical scale has been altered).

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Very wet scenario LVOS maximum levels Capacity 2014/15 Actual


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Figure 15: Original Lake Victoria storage outlook.

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Figure 16: End October Lake Victoria storage outlook.

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480 GL

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Very wet scenario Nominal Capacity NSW ML Reserve Last Season 2015-16


Figure 17: Original Menindee Lakes storage outlook.

480 GL

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Wet scenario Nominal Capacity NSW ML Reserve Last Season 2015-16


Figure 18: End October Menindee Lakes storage outlook.

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Figure 19: Original Menindee Lakes release outlook.

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Figure 20: End October Menindee Lakes release outlook.

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Wet scenario Very wet scenario Last Season 2015-16


Figure 21: Original flow to South Australia outlook.

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Figure 22: End October flow to South Australia outlook (note: vertical scale has been altered, and the dry scenario assumes delivery of more environmental water).

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