After almost three months travel time, the flood peak in the Darling River has arrived at the Menindee Lakes.Inflows of nearly 60,000 megalitres per day were experienced during the third week of April, but are now falling and have now reduced below 40,000 megalitres per day. Airspace in the lakes minimised the flood impact around Menindee township and downstream. Upstream at Wilcannia, the river is falling steadily and no further rises are anticipated from this event.
High flows generated from major floods in northern NSW and southern Queensland catchments during January
have merged and around 4,400 gigalitres has passed through Bourke so far in this event. The peak reached Tilpa
this week with the Darling River rising to a peak of 12.9 meters and a flow of 130,000 megalitres per day. Peak
flows are expected to reach Wilcannia in about 10 to 12 days time and arrive at Menindee in mid-April. The NSW
Office of Water and State Water Corporation are continuing to manage operations at Menindee Lakes in
anticipation of the forecast inflows.
Management of Menindee Lakes
Issue 4 – 24 February 2012
Major flood flows were generated from northern NSW and southern Queensland catchments during January and are making their way into the Darling River. The NSW Office of Water and State Water Corporation are continuing to manage flood operations at Menindee Lakes in anticipation of the impending substantial inflows. Two significant flood peaks are approaching Bourke; from the east (Barwon River) and from the north Culgoa/Bokhara River systems). They are forecast to merge during the first week of March, with the Barwon River flows expected to arrive slightly earlier than those from the Queensland Rivers. The scale of this event at Bourke and downstream is expected to be at least the peak level of 13.
Heavy rainfall and flooding in northern NSW and Queensland has triggered pre-releases from the Menindee Lakes system for the third time in two years. With the Menindee lakes storage levels already increasing as a result of high flows earlier this summer, there is limited capacity to manage the impending additional flow.
As a result, the NSW Office of Water and State Water Corporation began flood pre-release operations on Thursday 2 February 2012, increasing releases from 15,000 megalitres per day to a target of 29,000 megalitres per day by Tuesday 14 February. However, as the scale of flooding in the upstream valleys is becoming apparent, the rate of releases from
Menindee Lakes will now continue to rise further to target 35,000 megalitres per day by Friday 17 February. These releases to the Lower Darling will make room in the storage for the second period of high inflows that are expected to arrive in March and April 2012, and will protect the township of Menindee from extensive flooding. Currently the various flood peaks are still making their way along the Gwydir, Namoi, Moonie, Warrego and Balonne/Culgoa/Bokhara river systems. Flood flows from the Moonie, Namoi and Gwydir Rivers will flow into the Barwon-Darling system first, followed by flood flows from the other Queensland Rivers. The full extent of these flood flows into the Barwon-Darling system is not yet fully clear, but it is expected to be
significantly larger than last summer, with flood peaks even higher than those experienced in 1998. This could result in the largest flood in the Barwon-Darling system since 1976.
The south-west region received widespread rainfall during the past week. Of note is the significant rainfall in the eastern parts of the region during this period particularly in the Upper Condamine and Gowrie/Oakey Creek systems. Rainfall totals of between 150–350mm were recorded throughout both systems which resulted in major flooding in most areas of the upper Condamine catchment. This flow has continued downstream and has been bolstered by additional inflow from Charleys Creek and other Condamine tributaries. This renewed flood flow will prolong the current flooding throughout the Balonne and lower Balonne systems. High rainfall in the Border rivers catchment is also resulted in major flood flows in the Dumaresq and Macintyre/ Weir Rivers.
The majority of Queensland’s Murray Darling river systems have been flowing at various rates
since late September/early October 2010 with the majority of the moderate to major flooding
occurring in the Condamine/Balonne river systems in the last few weeks. The major flow activity
at this point in time relates to the eastern part of the QMDB with high flows present in the Border, Moonie and Condamine/Balonne catchments. Currently the Bureau of Meteorology has announced flood warnings for the Condamine, Moonie and Macintyre/Weir Rivers.
Water harvesting announcements continue for the Border & Weir Rivers in the south, Lower
Balonne, Upper Condamine Water Management Area, North Branch of the Condamine River and the Warrego River.
The report is an update of streamflow conditions in the South West and was prepared on the 17th January, 2011. Please note that some flow data is not yet available for use in this report due to gauging station infrastructure damage in some areas as a result of the significant flood events seen in the South west region in the past month.
Significant flooding events were recorded by the DERM streamflow gauging stations with hydrographers at their busiest across south west region during January, particularly the Condamine/Balonne River and Lower Balonne systems. Record heights were observed in parts of the system including Loudouns Bridge and Cotswold on the Condamine River, the Balonne River at Surat and the Culgoa River at Whyenbah. Good flows also occurred in the Border Rivers system and smaller flows were recorded in most other systems including the Paroo, Bulloo and Moonie Rivers. Currently, discharge is diminishing in all systems as the mass of flood water moves into NSW with little or no rainfall in the last week to bolster flow over most of
the region. While diminishing, significant flows are still being recorded in the Condamine/Balonne system, particularly in the Lower Balonne. The Bureau of Meteorology has announced minor to major flood warnings for the Balonne River. All eyes are currently focused on the approaching cloud mass of cyclone Yasi which could have some influence on rainfall and resurgence of flows in the southwest in the coming week.
Water harvesting announcements continue for the Border & Weir Rivers in the south, Lower Balonne and Upper Condamine Water Management Areas.
This report is an update of streamflow conditions in south west region and was prepared on the 1st February,2011