After a decade of below average rainfall across most of the Murray-Darling Basin, changing weather patterns delivered average to above average rainfall in 2010. This saw substantial increases in water availability in all major regulated systems across the NSW Murray-Darling Basin.
Rainfall from December 2009 to March 2010 saw flood flows move through the Barwon-Darling system and fill the Menindee Lakes.
Consistently good to high rainfall throughout 2010 and 2011 has seen NSW dam levels rise to capacity and made access to supplementary flows available in the southern Murray-Darling Basin valleys regularly since September 2010. Improvement in water availability has also enabled environmental flows to be delivered across NSW.
All drought management strategies have now ended and licensed water users have transitioned back to their relevant water sharing plan. All suspended water sharing plans recommenced in July 2011.
Water availability during high flows or flood
During periods of high flow, water is shared in accordance with the water sharing plan. During periods of drought, water sharing plans may be suspended. When flows increase, water sharing is conducted as close to the plan rules as possible, in preparation for plan recommencement.
In the case of very high and flood flows, the NSW Office of Water works with State Water Corporation and the State Emergency Service to manage flows and provide timely information to affected communities.
For more information on water sharing, go to Water sharing plans or contact the NSW Office of Water.
Monitoring water during flood
Data collection and dissemination plays a crucial role in day-to-day water management activities across the state. During flood events this role becomes even more critical for both flood forecasting and flood management. NSW Office of Water's network of over 700 telemetered water monitoring sites is a critical element in decision making by key agencies such as Bureau of Meteorology and the State Emergency Services. The timely delivery of information on flood levels and flood flows enables these agencies to perform their roles in producing flood watches and flood warnings, and undertaking evacuations and rescues during high rainfall events.
The Office of Water also provides the basic data for the management of flood flows through government-owned storages managed by the State Water Corporation and the Murray-Darling Basin Authority. These operations are aimed at both mitigating flood peaks and deriving the maximum long-term storage benefit from flood events.
During major events many Office of Water staff are on 24/7 alert to ensure that the field, computer and communication systems are operating effectively in their data collection and delivery roles so that key agencies and the broader community are kept reliably informed.
Field staff also actively seek to obtain discharge measurements during large flood events to confirm and update the stage discharge relationships through the physical collection of flood flows within the main stream and across the floodplains.
For up to date information on river and stream levels, go to Real-time data > Rivers and streams.
Lake Jindabyne reduction – March 2012
Due to high rainfall and significant inflows into Lake Jindabyne in early 2012, a total of 80 gigalitres of water was released into the Snowy River system below Jindabyne Dam from Tuesday 20 March 2012 with a gradual increase to 12,000 megalitres for one day on Monday 26 March. The flows were slowly decreased to 100 megalitres per day by Sunday 8 April. A pattern of the releases is shown in the graph below.
Graph: Proposed releases to the Snowy River, March 2012
The release was intended to reduce water levels in the lake, and ease the impact on businesses and facilities adjacent to Lake Jindabyne that were affected at full supply level. A secondary benefit to the flows was the ability to potentially provide flood mitigation capacity for downstream users during winter.
For more information, view the documents below:
NSW Office of Water review of water management during the 2010 flood events in the Tumut and Murrumbidgee Rivers
Floods in the Tumut and Murrumbidgee Rivers in October and December 2010 caused significant community anxiety. There was concern that water released by Snowy Hydro Limited for an extended period may have exacerbated flooding and worsened erosion.
NSW Office of Water has conducted a detailed review of water management in the lead up to the floods and examined responses by the relevant agencies. The Review of water management during the 2010 flood events in the Tumut River and Murrumbidgee River (PDF 3 MB) describes a number of actions taken both during and after the flood event and explains the legislative framework that guides water managers in the region.
Flood flows to the NSW Lower Murray
Community information: 2012
High flows generated from major floods in northern NSW and southern Queensland catchments in December and January, as well as flood flows generated from rainfall in late February in the Murray and Murrumbidgee valleys will reach the Murray River over April.
Information about flow rates and river heights for the flood flows in the Murray is available in the following communique:
Flood flows to the Menindee Lakes
Community information: February 2013 onwards
Heavy localised rainfall in southern Queensland and northern NSW during the last week in January 2013 triggered large flows to some inland rivers. These flows are slowly entering the Barwon-Darling river system. The increased flows are likely to reach the Menindee Lakes in late-March 2013.
Community information: December 2011 to May 2012
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.
The NSW Office of Water is implementing flood operations at the Menindee Lakes to reduce the risk of downstream flooding when near record flows in the upper Darling reach the Lakes.
A summary report on the management of this flood event has been prepared by the Office of Water. Download Management of the Barwon-Darling Floods of November 2011 - June 2012 (PDF 2 MB).
Information about flow rates and river heights for this summer's flood events in the Barwon-Darling River system is available in the following communiques:
Community information: 2010-2011
Heavy widespread rainfall and flooding occurred across much of northern NSW in November and December 2010 for the second year in a row. The flows from these summer storms made their way slowly along the Barwon-Darling system reaching the Menindee Lakes during March and April 2011.
While this event at Menindee was not the largest historically, it proved particularly challenging because the Menindee Lakes was already full and circumstances were exacerbated by periodic heavy rainfall at Menindee during the floods.
Nevertheless, the NSW Office of Water together with infrastructure operator State Water Corporation, successfully passed the flood waters through the system and managed the downstream recession without damage to water infrastructure and river banks. Peak inflows of over 50,000 megalitres per day (ML/d) were reduced to a maximum outflow of 37,000ML/d, thereby sparing the township of Menindee from higher floodwaters.
A summary report on management of this flood event has been prepared by the Office of Water. Download Summary Report - Management of the Barwon-Darling Floods of December 2010–April 2011 (PDF 5 MB)
During this high flow event NSW Office of Water issued community information updates which can be accessed from the list below:
Community information: March to May 2010
After a prolonged drought, significant rainfall was welcomed across Queensland and northern New South Wales in the early months of 2010. NSW Office of Water issued flood flow updates between 19 March and 28 May. These updates can be accessed from the list below.
Floods in 2010 replenish the Paroo River
Highly significant flooding occurred along the Paroo River in March and April 2010, with river flows reaching 100,000 megalitres per day at Willara Crossing between Hungerford and Wanaaring on 12 March 2010.
The floods, which had not occurred at this magnitude for several decades, reinvigorated the river's pools and wetlands, which provide an important habitat for waterbirds and other aquatic organisms. The floodwaters, mainly from Queensland, flowed into the Darling River about 30km upstream of Wilcannia also providing relief for water users downstream. The flows recharged Paroo River and its aquifers with organic matter essential for river function and productivity.
Further study by the NSW Office of Water will determine the effect of man-made flow barriers on flows using high-resolution aerial photography. The Office of Water is also leading the development of water sharing plans for intersecting streams such as the Paroo and Warrego.
During flood events, large amounts of information about flood behaviour and measured volumes of water is collected and stored within NSW Office of Water databases. This information is used in future water modelling projects to better understand the hydrology of river systems and to aid long term water and flood management.