Community information. Management of Menindee Lakes 2010-2011…€¦ · NSW Office of Water |...
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The NSW Office of Water is a separate office within the Department of Environment, Climate Change and Water INTRODUCTION Inflow from the flood in the Barwon-Darling River, caused by floods in the McIntyre, Macquarie and Namoi Rivers in November and December last year is now reaching the Menindee Lakes with the peak expected in the next three weeks. The peak of this event is now passing Tilpa where the river is steady at 79,000 megalitres per day (ML/d). Upstream at Bourke the river flow is 61,000 ML/d and continuing to fall from a peak of 88,000 ML/d on 11 January. However, the river level is expected to rise again over the coming week to levels slightly higher than the January peak as flows arrive from the first peak in the Culgoa River that peaked at St George at 290,000 ML/d on 9 January. A second peak was recorded at St George of 244,000 ML/d on January 23. This was a result of the torrential rainfall event across much of southern Queensland, including the flows that caused significant damage in Toowoomba. This will reach Bourke a couple of weeks later. The flows from the first of these events are expected to reach the Menindee Lakes about mid March. Flows from the Macintyre River, that peaked at Boggabilla at 270,000 ML/d on 14 January, will probably reach Bourke between the two St George peaks. Consequently, flows at Bourke will remain high throughout March and into April and will ensure a high river at Wilcannia until well into May. The river level at Wilcannia has now risen slowly to about 30,900 ML/d. Interestingly, the flow has risen very little over the past 14 days. This is possibly because more water is going into the lakes off the Talyawalka anabranch that flows out of the Darling River upstream of Wilcannia. Darling River downstream of Menindee (near the old abattoirs) 24 January 2011 (photo courtesy Barry Philp, State Water) Community information Management of Menindee Lakes 2010-2011 January 28, 2011
Transcript of Community information. Management of Menindee Lakes 2010-2011…€¦ · NSW Office of Water |...
The NSW Office of Water is a separate office within the Department of Environment, Climate Change and Water
INTRODUCTIONInflow from the flood in the Barwon-Darling River, caused by floods in the McIntyre, Macquarie and Namoi Rivers in November and December last year is now reaching the Menindee Lakes with the peak expected in the next three weeks. The peak of this event is now passing Tilpa where the river is steady at 79,000 megalitres per day (ML/d).
Upstream at Bourke the river flow is 61,000 ML/d and continuing to fall from a peak of 88,000 ML/d on 11 January. However, the river level is expected to rise again over the coming week to levels slightly higher than the January peak as flows arrive from the first peak in the Culgoa River that peaked at St George at 290,000 ML/d on 9 January.
A second peak was recorded at St George of 244,000 ML/d on January 23. This was a result of the torrential rainfall event across much of southern Queensland, including the flows that caused significant damage in Toowoomba. This will reach Bourke a couple of weeks later.
The flows from the first of these events are expected to reach the Menindee Lakes about mid March.
Flows from the Macintyre River, that peaked at Boggabilla at 270,000 ML/d on 14 January, will probably reach Bourke between the two St George peaks. Consequently, flows at Bourke will remain high throughout March and into April and will ensure a high river at Wilcannia until well into May.
The river level at Wilcannia has now risen slowly to about 30,900 ML/d. Interestingly, the flow has risen very little over the past 14 days. This is possibly because more water is going into the lakes off the Talyawalka anabranch that flows out of the Darling River upstream of Wilcannia.
Darling River downstream of Menindee (near the old abattoirs) 24 January 2011 (photo courtesy Barry Philp, State Water)
Community information Management of Menindee Lakes 2010-2011January 28, 2011
www.water.nsw.gov.au NSW Office of Water | Issue 3 – January 28, 2011 page 2
Management of Menindee Lakes 2010-2011 – January 28, 2011
It is still too early to predict with confidence the volumes and peaks of flow that will enter the Barwon-Darling River from the floods upstream, but it is likely to rank with some of the highest inflows in the past 25 years. Some sites, such as Brenda, on the Culgoa River at the Queensland-NSW border, had its highest flow since 1890.
Heavy rainfall in western NSW, particularly around Menindee, Wilcannia and White Cliffs two weeks ago generated a lot of local run-off, increasing river levels quickly as well as adding a lot of volume to the lakes. State Water Corporation acted quickly to manage the releases from the main weir so that lake levels stayed relatively constant.
However, the local rainfall and run-off reduced the available airspace in the lakes. This airspace needs to be recovered in order to capture the peak of the high flow volumes currently in transit to Menindee to reduce, where possible, the flood impacts immediately downstream of the lakes. By having airspace available, there is some capacity to absorb the impact of any further heavy rainfall events that may occur in the coming months.
Consequently, it will be necessary to increase releases from the Menindee Lakes to the Lower Darling River to 38,000 ML/d at Weir 32 by early February. This corresponds to a pool level at Weir 32 of 7.14 metres.
The flow at Weir 32 is currently 32,200 ML/d and rising. By increasing releases as proposed the total lake storage volume will fall for a few weeks before rising again as the higher flood inflows reach Menindee.
The forecast level at Weir 32 is expected to result in some access and infrastructure impacts at Menindee with about 10 houses immediately downstream of Menindee being surrounded by water (floors not inundated), two with inundation and the Pooncarie Road being cut approximately 12 kms south of Menindee.
It is hoped that further increases in the release rates from the Menindee Lakes above 40,000 ML/d at Weir 32, which corresponds to a pool level of 7.22 metres, will not be necessary. However, this cannot be ruled out at this relatively early stage. The situation is being closely monitored and more certainty will be provided as soon as practicable through regularly information updates.
The NSW Office of Water, together with State Water are managing releases from the Menindee Lakes to the Lower Darling River and Great Anabranch to minimise the impacts on private property, maximise environmental benefits downstream and to make sure that the lakes are full when the floods have passed.
CURRENT FLOW MANAGEMENT
Location Height (m) Flow (ML/d) Comment
Boggabilla 2.10 5,683 Falling (Peak 270,000 on 14/1/11)
Mungindi 7.66 27,657 Falling (Peak 28,200 on 26/1/11)
Collarenebri (total) 5.48 33,465 Rising
Walgett 10.06 26,550 Rising
Brewarrina (total) 5.63 34,196 Falling
Bourke 11.40 61,075 Falling (Peak 87,600 on 13/1/11)
Louth 11.95 76,695 Falling (Peak 84,000 on 21/1/11)
Tilpa 12.28 79,586 Peaking
Wilcannia 9.84 30,901 Rising
Weir 32 6.91 32,460 Rising
Pooncarie 6.83 15,399 Steady
Burtundy 6.75 16,501 Steady
River data from 27 January 2011
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Darling River Flows and Menindee Storage VolumeDarling River Flows and Menindee Storage Volume
0
20,000
40,000
60,000
80,000
100,00029
-Sep
-10
06-O
ct-1
0
13-O
ct-1
0
20-O
ct-1
0
27-O
ct-1
0
03-N
ov-1
0
10-N
ov-1
0
17-N
ov-1
0
24-N
ov-1
0
01-D
ec-1
0
08-D
ec-1
0
15-D
ec-1
0
22-D
ec-1
0
29-D
ec-1
0
05-J
an-1
1
12-J
an-1
1
19-J
an-1
1
26-J
an-1
1
02-F
eb-1
1
09-F
eb-1
1
Flow
(ML/
d)
1,500,000
1,600,000
1,700,000
1,800,000
1,900,000
2,000,000
2,100,000
2,200,000
Stor
age
Volu
me
(ML)
Menindee Storage
Bourke Flow
Weir 32 ReleaseWilcannia Flow
Forecast Conditions -approximate only.
Menindee Storage
WHAT THIS MEANS The outlook for the Lower Darling is for flows of about 20,000 ML/d (7.4 m gauge height) and minor flooding at Burtundy by mid February, with further increases to around 24,000 ML/d (8.0 m gauge height) possible by late February or early March. This would make this event larger than that of 1998 (21,600 ML/d and 7.7 m) but much smaller than the huge flood of 1976 (59,000 ML/d and 9.7 m) at Burtundy.
Also, these flows are relatively small compared with flows in the Murray expected in the vicinity of 80,000 ML/d near the confluence with the Lower Darling. Nevertheless the outflow from the Lower Darling (and the Great Darling Anabranch) to the Murray is expected to be sustained for a prolonged period, potentially through to May.
Current releases from the Menindee Lakes are:
ML/d
Main weir 35,000
Lake Wetherell outlet 1,500
Lake Pamamaroo outlet -
Lake Menindee outlet -
Lake Cawndilla outlet 1,750
Total 38,250
HOW THIS FLOOD COMPARES TO PREVIOUS EVENTSThis section is shown to enable the comparison of the current flood events with previous floods.
Year Max height at Bourke (m)
Total volume at Bourke (GL)
Max height at Wilcannia (m)
Total flows at Wilcannia (GL)
Max height Weir 32 (m)
1988 12.57 3,500 10.19 2,600 5.10
1996 12.39 2,500 9.85 2,400 5.18
1998 13.78 9,700 10.83 4,200 7.45
2001 12.28 3,300 9.75 2,250 6.21
2010 10.78 2,370 9.43 2,400 5.44
www.water.nsw.gov.au NSW Office of Water | Issue 3 – January 28, 2011 page 4
Management of Menindee Lakes 2010-2011 – January 28, 2011
© State of New South Wales through the Department of Environment, Climate Change and Water, 2011 This work may be freely reproduced and distributed for most purposes, however some restrictions apply. Contact the Department of Environment, Climate Change and Water for copyright information.
Disclaimer: While every reasonable effort has been made to ensure that this document is correct at the time of publication, the State of New South Wales, its agencies and employees, disclaim any and all liability to any person in respect of anything or the consequences of anything done or omitted to be done in reliance upon the whole or any part of this document. This information does not constitute legal advice. Users are advised to seek professional advice and refer to the relevant legislation, as necessary, before taking action in relation to any matters covered by this information sheet.
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ENVIRONMENTAL MANAGEMENTInflows from upstream flooding and local rainfall and run-off have increased the total volume being stored in the Menindee Lakes and water is now inundating the Lake Wetherell floodplain. The Office and Water tries to get water off the floodplain as a priority to kee p the floodplain vegetation alive and to maintain habitat for native species. Clearly, with the volumes of water expected to reach Menindee, all of the lakes are expected to be surcharged to their capacity in the coming weeks and months.
Releases are continuing from Lake Cawndilla to the Great Anabranch, providing much needed environmental benefits after such a long drought. Flows are continuous for the length of the Anabranch to the Murray River and are filling some of the Anabranch Lakes that are listed in the Directory of Important Wetlands in Australia.
Yabbie taken from the Menindee Lakes (Photo courtesy of Barry Philp, State Water, January 2011)
COMMUNICATION AND ADDITIONAL INFORMATIONThe Office of Water and State Water will continue to prepare and publish this series of information sheets every two weeks where possible.
A regional committee, that includes representatives of water users from the Menindee, Lower Darling and Great Anabranch has been established to ensure that available information is distributed about river levels and flow management.
The NSW Office of Water and State Water will continue to work with the SES, local police and councils.
WHERE DO I GO FOR ADDITIONAL INFORMATION? NSW State Water office in Cawndilla Street Menindee.
SES free call 132 500
NSW Office of Water: call Bunty Driver T 03 5898 3910 or visit the website www.water.nsw.gov.au
