Significant water events
Rainfall across large areas of the Murray–Darling Basin (MDB) region was below average during the 2012–13 year, contrasting strongly with the previous two years when above average rainfall was recorded. The annual pattern of rainfall was typical of the long-term average for the region with a return to hot and dry weather during the summer months for most of the region; however, during January 2013, contrasting extremes affected most of the region: a record heatwave was accompanied by very low rainfall during Australia's hottest month on record, and later in the month, the upper Condamine and Border rivers catchments in the north-eastern part of the MDB region experienced record-breaking rainfall generated by ex-tropical cyclone Oswald (Bureau of Meteorology 2014 and Murray–Darling Basin Authority 2014a).
Remarkably heavy rain fell at some locations near the New South Wales–Queensland border, although a relatively steep gradient to lighter rain inland of the Great Divide meant that downstream flood peaks and volumes were mostly a lot smaller than those experienced during the Darling system flood events of the 2010–12 year.
Drying later in the year caused by hot weather and low rainfall meant that inflows receded steadily during spring and summer, remaining largely below long-term averages. The six-month period from August 2012 to January 2013 was particularly dry across the MDB region, with western and south-western areas most affected.
Snowy Hydro Limited made above target releases, 377,000 ML to the Murray River and 74,000 ML to the Tumut River (Murrumbidgee catchment), as discretionary flows during the 2012–13 year (Snowy Hydro Limited 2014).
New South Wales
Total inflows to Menindee Lakes between July 2012 and June 2013 were considerably lower than during the previous two years, although the total of about 1,500,000 ML was still higher than the long-term median annual inflow of about 950,000 ML. The inflows were mostly generated by rain events over the upper Darling system tributaries during the 2012 winter and during late January 2013 (Murray–Darling Basin Authority 2014a).
Storage levels at the Menindee Lakes began the year with over 100% capacity. Persistent rainfall during July over the northern NSW catchments increased flows along the Gwydir and Namoi rivers to peaks that exceeded moderate flood levels at several gauges. These flows caused a peak flow in the Darling River at Bourke during early August close to 16,000 ML/day and peak inflows to the Menindee Lakes of around 10,000–15,000 ML/day during late August that increased the storage volume to 2,037,000 ML, just below the full surcharge capacity of 2,050,000 ML.
The Murray–Darling Basin Authority requested regulated releases from Menindee Lakes on 19 October 2012 to supplement flows in the River Murray and regulated releases continued until the end of May 2013. The highest regulated release rates occurred during December 2012 and April 2013 with a peak of about 9,000 ML/day and the storage volume fell to a low of about 50% capacity by March 2013 (Murray–Darling Basin Authority 2014a).
Inflows receded to low levels during the period from spring 2012 to late summer 2013 before the year's second inflow event commenced in March 2013. The event was triggered by extremely heavy rainfall generated by ex-tropical cyclone Oswald over the upper Condamine and Border rivers catchments during January 2013. About 950,000 ML flowed into Menindee Lakes between March and May 2013 from this event (Murray–Darling Basin Authority 2014a).
The northeastern part of the MDB region experienced heavy rainfall in late January, generated by a cyclone. This event caused major flooding along several Barwon–Darling system tributaries during the second half of the 2012–13 summer (Murray–Darling Basin Authority 2014a).
South Australia began the year with its full entitlement of 1,850,000 ML for the second consecutive year. Additional dilution flow delivered to South Australia from 1 August 2010, came to an end on 7 January 2013 when the Menindee Lakes storage volume decreased below the required monthly trigger volume: 1,300,000 ML for January (Murray–Darling Basin Authority 2014a).
Between October 2012 and June 2013, South Australia's entitlement flow was further boosted by the addition of more than 900,000 ML of traded environmental water. The total annual flow across the South Australian border, including additional dilution flow, unregulated flow, environmental water and traded water, was about 7,000,000 ML compared with 10,300,000 ML in the previous year. The long-term median annual flow to South Australia is 5,200,000 ML.
At the start of 2012–13, storage was 3,351,000 ML in Dartmouth Reservoir (86% of capacity) and 2,902,000 ML at Hume Reservoir (96% of capacity). High flows with minor flooding occurred along the upper River Murray System tributaries during July and August 2012. Storage in Dartmouth Reservoir increased to 99% capacity by October 2012 when the reservoir was considered to be 'effectively full'. Releases were increased above minimum (200 ML/day) from 25 October to pass inflows and maintain the storage volume at about 99% capacity. The last time Dartmouth Reservoir was at 99% capacity or above was early in 1997.
At Yarrawonga Weir, the release peaked at 53,000 ML/day on 22 July 2012, with another peak in excess of 40,000 ML/day during late August. Flows generally receded throughout the spring although two smaller peaks above channel capacity occurred during early October and early November. To reduce the risk of undesirable overbank flooding in the Barmah–Millewa Forest, the target release from Yarrawonga Weir during the main irrigation period was generally 8,000 to 9,000 ML/ day. However, because of rain events and hot weather the actual release varied between 6,000 and 11,000 ML/day (Murray–Darling Basin Authority 2014a).
Rainfall across the MDB region was generally below average for the 2012–13 year. The area-averaged monthly rainfall was below the long-term average during the 2012–13 year except for July 2012, March 2013, and June 2013.
Figures W1–W3 show streamflow patterns, volumes and variations for the three gauging stations selected for the flow analysis for the 2013 Account (see Surface water streamflow summary for gauging station details).
Figure W1 Graph of total monthly flow during the 2012–13 year compared against long-term percentiles for the Murray River at Doctors Point (Albury)
Source: Bureau of Meteorology.
Figure W2 Graph of total monthly flow during the 2012–13 year compared against long-term percentiles for the Darling River at Bourke
Source: Bureau of Meteorology.
Figure W3 Graph of total monthly flow during the 2012–13 year compared against long-term percentiles for the Ovens River at Peechelba
Source: Bureau of Meteorology.
Streamflow analysis for the three stations shows that the streamflows were above mean annual flow for the Murray River at Doctors Point, just above mean annual flow for Ovens River at Peechelba, and well below mean annual flow for the Darling River at Bourke (figures W1–W3) for the 2012–13 year.
The year started with above average flows and then changed to below average flows towards the end, with the exception of January and April 2013 for the Murray River system. Inflows in the Murray River system in the 2012–13 year broadly followed the long-term seasonal distribution. Wet catchments in the upper Murray system tributaries before winter 2012 resulted in good responses to rain events although total rain during June and July was only about average. July 2012 inflows were the highest since 1995, and August 2012 inflows were also above the long–term average.
Although streamflows were above mean annual flow for the Murray River at Doctors Point for the 2012–13 year, the distribution of the rainfall, and ongoing above-average temperatures, meant that inflows from the River Murray System tributaries were generally below average. Total inflows to the River Murray System for the 2012–13 year (including inflows to the Menindee Lakes but excluding releases from the Snowy Mountains Scheme) were around 9,200,000 ML, placing the year a little below the long–term mean (Murray–Darling Basin Authority 2014a).
The year started with above average flows and then changed to below average flows towards the end, with the exception of April 2014 for the Darling River. Monthly flows in the Darling River were highly variable and low compared to the Murray River flows. As a result, Northern Basin contribution to the water availability in the Southern Basin was relatively small.
Major water initiatives
The proposed Murray–Darling Basin Plan was released in May 2012. The Minister for Sustainability, Environment, Water, Population and Communities adopted it in November 2012. The Basin Plan 2012 builds on and complements previous water reforms aiming to balance the water needs for different uses by establishing sustainable diversion limits (SDLs) for the Murray–Darling Basin catchments.
A key element of the Basin Plan 2012 is the setting of SDLs, on the amount of water used in the MDB region. SDLs will be implemented through the Basin Plan-consistent water resource plan for each water resource plan area, and will be in effect from 1 July 2019. The plan has specified a long-term SDL of 10,873,000 ML per year for surface water. This would result in an additional 2,750,000 ML per year of water returned to the rivers within the MDB region. The Basin-wide long-term average total SDLs for groundwater is 3,334,000 ML per year.
Australian Capital Territory
The 2013 Account for the Canberra region includes information on major water initiatives applicable for the Australian Capital Territory.
New South Wales
Several water sharing plans commenced during the 2012–13 year. They are:
- Water Sharing Plan for Barwon–Darling Unregulated and Alluvial
- Water Sharing Plan for Belubula Regulated River
- Water Sharing Plan for Lachlan Unregulated and Alluvial
- Water Sharing Plan for Macquarie Bogan Unregulated and Alluvial
- Water Sharing Plan for Murrumbidgee Unregulated and Alluvial
- Water Sharing Plan for Namoi Unregulated and Alluvial
- Water Sharing Plan for Gwydir Unregulated and Alluvial.
On 30 March 2012, the Queensland Government announced machinery-of government changes for departments. The functions of the former Department of Environment and Resource Management are now delivered by the Department of Environment and Heritage Protection, the Department of Natural Resources and Mines (responsible for administering the Queensland Water Act 2000), the Department of National Parks, Recreation, Sport and Racing, and the Department of Energy and Water Supply.
A review of Warrego, Paroo, Bulloo, and Nebine Water Resource Plan and the Resource Operations Plan commenced in the 2012–13 year.
A new department, Department of Environment, Water and Natural Resources, has taken on the water responsibilities (held by Department for Water during the 2011–12 year) effective from 1 July 2012.
Following groundwater management plans commenced during the 2012–13 year:
- Lower Campaspe Water Supply Protection Area (WSPA) Groundwater Management Plan (this plan has replaced the earlier Campaspe Deep Lead WSPA and Southern Campaspe Plains groundwater management area plans)
- Loddon Highlands WSPA Groundwater Management Plan (this plan has replaced the earlier Spring Hill and Upper Loddon WSPA plans).