Significant water events
Frequent heavy rain events from spring 2010 to autumn 2011, and again in late 2011, led to Australia's wettest two-year period on record. The heavy rainfall during these periods ended a record sequence of dry years in the southeast of Australia (Bureau of Meteorology 2013a).
In the upper Darling catchment, significant rainfall events occurred in late November 2011 and in late January – early February 2012 (Murray–Darling Basin Authority 2013c). Record peak flows were observed along the Maranoa and Balonne rivers, with very high river levels also recorded along the Paroo, Warrego, Moonie, Weir, McIntyre, Gwydir and Namoi rivers. The large number of rivers flooding simultaneously resulted in major flooding in the Darling River at Bourke, New South Wales, where flow reached 237,000 ML per day in March 2012, the highest flow at Bourke since the 500,000 ML per day recorded in March 1976.
For the Murray-Darling Basin (MDB) and the southern part of New South Wales, including northern Victoria, seven days from 27 February 2012 was the wettest seven-day period on record for any month with the Murrumbidgee catchment accumulating 202.6 mm rainfall (Bureau of Meteorology 2013b). The Murrumbidgee River peaked at 10.9 meters near Gundagai, with major flooding at Gundagai and Wagga Wagga. Major flooding was also recorded along the Lachlan River and the Mitta Mitta River.
The March 2012 inflow within MDB was the highest on record, double the previous record set in the 2010–11 year, and the inflow in April was the second highest on record (Murray–Darling Basin Authority 2013c). Heavy rainfall brought high-flowing rivers replenishing water storages and rejuvenating wetland and floodplain ecosystems..
As a result of high inflows approximately 362,508 tonnes of salt was diverted from the River Murray through salt interception schemes. The basin-wide salinity target was also met, with peak salinity at Morgan, South Australia remaining below 800 EC in the 2011–12 year (Murray–Darling Basin Authority 2013c).
New South Wales
Total inflows to Menindee Lakes between July 2011 and June 2012 were about 5,000 GL compared with the long-term median annual inflow of about 945 GL. The high inflows caused by two major rainfall events in northern New South Wales and southern Queensland (Murray–Darling Basin Authority 2013c).
The first event occurred in late November 2011, when heavy rainfall triggered large flows in the Gwydir and Border rivers and the Namoi catchment. These large flows caused a peak flow in the Darling River at Bourke of 73,000 ML per day and a peak inflow to Menindee Lakes of around 36,000 ML per day.
The second event, in late January and early February 2012, generated high flows in the Namoi, Gwydir, Moonie and the Balonne–Culgoa–Bokhara river systems. The Darling River experienced major flooding from this event, with a peak flow at Bourke of around 240,000 ML per day (major flooding) and a peak inflow to the Menindee Lakes of near 60,000 ML per day. From December 2011, the release from the lakes was increased to pass floodwater; by mid-April 2012, the release reached close to 36,000 ML per day (Murray–Darling Basin Authority 2013c).
Record peak flows were observed along the Maranoa and Balonne rivers, with very high river levels also recorded along the Paroo, Warrego, Moonie, Weir and McIntyre rivers due to significant rainfall events occurred in late November 2011 and in late January – early February 2012 (Murray–Darling Basin Authority 2013c).
The 2011–12 year was the first since 2002–03 that South Australia began the year with its full entitlement of 1,850 GL assured (MDBA 2013c). Additional dilution flow was delivered to South Australia during the 2011–12 year (continuing from the previous year), because the total volume of Hume and Dartmouth reservoirs exceeded 2,000 GL and the volume of Menindee Lakes exceeded the required monthly trigger volumes.
Between October 2011 and March 2012, the flow to South Australia included more than 350 GL of environmental water. The total annual flow across the South Australian border, including additional dilution flow, unregulated flow, environmental water and traded water, was about 10,200 GL. The long-term median annual flow to South Australia is 5,200 GL.
Flood operations were undertaken at Yarrawonga Weir in August 2011, with high flows from Hume Reservoir and from the Kiewa and Ovens river catchments with a peak release of 52,500 ML per day on 22 August (Murray–Darling Basin Authority 2013c). In late February to early March, 2012, 264 mm of rain fell at Yarrawonga, causing very high local inflows as well as inflow from the Kiewa and Ovens river catchments. Major flooding was also recorded along the Mitta Mitta River and record flooding in the Broken Creek during the same period. High flows were observed at Torrumbarry resulting in overbank flooding into the Gunbower and Koondrook–Perricoota forests several times during the 2011–12 year.
The rainfall associated with the La Niña event in the Pacific Ocean and warmer than average sea surface temperatures in the Australian region contributed to widespread flooding across several areas of the Murray–Darling Basin (MDB) region during the 2011–12 year, particularly in spring and summer. Details of how high streamflows contributed to severe flooding in the jurisdictions have been provided under Significant water events.
Figures W1–W3 show streamflow patterns, volumes and variations for the three gauging stations selected for the flow analysis for the 2011 Account (see Surface water streamflow summary for gauging station details).
Figure W1 Graph of total monthly flow during the 2011–12 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 2011–12 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 2011–12 year compared against long-term percentiles for the Ovens River at Peechelba
Source: Bureau of Meteorology.
Streamflows analysed for the 2012 Account for the stations within the MDB region were close to mean annual flow for the Murray River at Doctors Point, well above mean annual flow for the Darling River at Bourke and above mean annual flow for the Ovens River at Peechelba (figures W1–W3) for the 2011–12 year.
Major water initiatives
The Murray–Darling Basin Authority presented the draft proposed Basin Plan for the Murray–Darling Basin for public exhibition in November 2011. The Basin Plan was finalised in May 2012 for the Minister for Sustainability, Environment, Water, Population and Communities to adopt it in November 2012.
The Basin Plan builds on and complements previous water reforms aiming to balance the water needs for different uses by establishing sustainable diversion limits for the Murray–Darling Basin catchments.
Australian Capital Territory
The 2011–12 year starts with the Environment and Sustainable Development Directorate (formed on 17 May 2011) assuming water responsibilities in the territory.
Following the Water Security Review in 2007, the Australian Capital Territory Government announced a range of new water supply projects, which ACTEW Water continued to implement throughout the 2011–12 year.
enlarging Cotter Reservoir to increase the capacity to 78,000 ML (the construction activities continued during the 2011–12 year)
constructing Murrumbidgee to Googong water transfer pipeline (the construction activities continued during the 2011–12 year).
New South Wales
Several water sharing plans commenced during the 2011–12 year. They are:
Water Sharing Plan for the Castlereagh (below Binnaway) Unregulated and Alluvial Water Sources 2011
Water Sharing Plan for the Intersecting Streams Unregulated and Alluvial Water Sources 2011
Water Sharing Plan for the Lower Murray–Darling Unregulated and Alluvial Water Sources 2011
Water Sharing Plan for the Murray Unregulated and Alluvial Water Sources 2011
Water Sharing Plan for the NSW Border Rivers Unregulated and Alluvial Water Sources 2012
Water Sharing Plan for the Lower Murray Shallow Groundwater Source 2012
Water Sharing Plan for the NSW Great Artesian Basin Shallow Groundwater Sources 2011
Water Sharing Plan for the NSW Murray–Darling Basin Fractured Rock Groundwater Sources 2011
Water Sharing Plan for the NSW Murray–Darling Basin Porous Rock Groundwater Sources 2011.
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, the Department of National Parks, Recreation, Sport and Racing and the Department of Energy and Water Supply.
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.
The Adelaide desalination plant (ADP) has been producing drinking water since October 2011. Desalinated water mixes with water treated at the Happy Valley water treatment plant before entering the Happy Valley distribution network. The completed North–South interconnection system project (SA Water 2013) enables to deliver this desalinated water to customers in both Adelaide's northern and southern suburbs.
The Victorian Environmental Water Holder (Victorian Environmental Water Holder 2013) commenced operations on 1 July 2011. The Victorian Environmental Water Holder as an independent body is responsible for making decisions on the most efficient and effective use of Victoria's environmental water entitlements.