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House of Assembly - Fifty-Second Parliament, First Session (52-1)
2010-09-14 Daily Xml
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MURRAY-DARLING BASIN

The Hon. P. CAICA (Colton—Minister for Environment and Conservation, Minister for the River Murray, Minister for Water) (14:27): I seek leave to make a ministerial statement.

Leave granted.

The Hon. P. CAICA: I wish to inform the house about some of the likely impacts arising from the expected increased inflows into South Australia due to the recent rainfall across the southern Murray-Darling Basin. Areas in northern Victoria recently experienced extremely high rainfall over a short period resulting in flooding. After years of drought, this inflow has added significance for the River Murray in South Australia, with the anticipated additional water having significant benefits for the river's health and the health of the Lower Lakes region, for irrigators, communities, wildlife and tourism.

The Murray-Darling Basin Authority has indicated that South Australia will receive around 900 gigalitres of water from this flood event. I am advised that this figure cannot be confirmed at this point in time, but I expect to be able to provide a more accurate assessment over the coming weeks. The authority has confirmed that at least 190 gigalitres of unregulated flow will be received by South Australia, with the volume expected to increase in the coming weeks as more information emerges about the flood situation in Victoria.

It is important to note that large sections of the environment in this part of Victoria have received limited watering over the past decade and, with this event resulting in the inundation of large areas of floodplain, including Barmah Forest, much of this water will not return to the River Murray system. I am advised that unregulated flows cannot be captured in South Australia so they cannot be allocated for purposes such as irrigation.

This water will flow through the River Murray to the Lower Lakes and will provide the environment with a much-needed boost. In addition to unregulated flow, the authority has indicated that South Australia will receive a further 459 gigalitres of additional dilution flow to mitigate salinity in the River Murray and the Lower Lakes.

The state government and the federal Labor government have been prepared to take tough decisions, including investing in massive engineering works, the lowering of pumps along the river to depths not previously contemplated, and some wetlands have been disconnected and new pipelines have been constructed to ensure Lower Lakes communities continue to have access to water.

In this regard, the Narrung bund and Clayton and Currency Creek regulators were built to manage local acidification risks, and preparations for the Wellington weir had to be considered in contingency, despite vocal opposition and the state government maintaining its preference for a freshwater solution for the Lower Lakes.

We now have a very different landscape before us. The River Murray and the Lower Lakes, and the Coorong and Murray Mouth will see the first significant flows for about a decade, and effective management of natural and man-made infrastructure is pivotal to the successful recovery from the unprecedented drought. The current water level in Lake Alexandrina is about 50 centimetres above sea level, and it is expected to increase to 75 centimetres above sea level by early October, while the level in Lake Albert is about 30 centimetres below sea level. These are the highest water levels since 2005.

The improved water levels and access to additional water have provided the opportunity to reconnect Lake Albert with Lake Alexandrina. They will also allow us to open the barrages to discharge water into the Coorong, thereby reducing salinity in Lake Alexandrina, providing fish passage to the Coorong and slowly transitioning the Coorong from a marine to a more estuarine condition. Currently, small flows are being released through the barrages and fishways to assist fish passage and slowly re-establish an estuary beyond the barrages.

Yesterday I was advised by the authority that from today all fishways along the barrages will be open and that from 20 September additional bays adjacent to the fishways at Tauwitcherie barrage and Goolwa barrage will be opened. This pre-release of water now will enable more salt to be discharged from Lake Alexandrina. It is envisaged that considerably larger releases will be able to occur in coming months, allowing good flows of water into the Coorong and potentially out of the Murray Mouth.

While the refreshing of the Coorong is extremely welcome, it is still likely that we will need to pump sea water into the southern part of the Coorong this summer because of the hypersaline condition of that water body. The rising water level also provides an opportunity for many irrigators to access water for the first time in a number of years. For other irrigators, the rising water level places some modified or relocated infrastructure at risk of being inundated, and advice is being provided about relocating high-risk infrastructure as soon as possible.

An embankment was constructed between Lake Albert and Lake Alexandrina at Narrung in March 2008 as a short-term emergency measure to assist in the management of potentially devastating acidification in Lake Albert. On 10 September, I announced that because of the extra water in the River Murray system it is now possible to remove part of this structure and allow water to flow into Lake Albert. Preparatory work to remove 100 metres of the 280-metre structure began over this past weekend, and the first water is set to flow into Lake Albert early next week. It is expected that water levels in Lake Alexandrina and Lake Albert will equalise within two months.

Full removal of the bund will occur when the authority can confirm that water levels in the Lower Lakes will not fall below sea level before the end of 2011-12 under a worst case scenario. Just over a year ago, temporary environmental flow regulators were constructed at Clayton and Currency Creek as part of the Goolwa Channel water level management project to mitigate the very real threat of acidification in the Goolwa Channel and its tributaries. Partial removal of the Clayton regulator may soon be possible, restoring a connection between Lake Alexandrina and the Goolwa Channel, enabling releases of water through the Goolwa barrage. The use of all barrages during a large release is necessary to ensure the Murray Mouth is maintained in a stable state.

Discharges from the Goolwa barrage fishway will enable the unrestricted movement of fish species between the Lakes and the Coorong. Discharges from the Goolwa barrage will result in reduced salinity in the Goolwa Channel, which will have a positive benefit on the freshwater ecosystem. If this unregulated flow event can restore the water level in the Lower Lakes so that it does not fall below sea level before the end of 2011-12, then acidification in the Lower Lakes can be managed without the Clayton regulator in place.

At this stage, there is no requirement to remove the Currency Creek regulator as it has a spillway that maintains the connection of Currency Creek to the Goolwa Channel at water levels above sea level. Another benefit of the increased flows to South Australia is that there will be significant delay in the need to make a decision on constructing a weir near Wellington or the opening of the barrages to allow sea water into the Lower Lakes to manage acidification. The extra water means that the triggers for those actions are unlikely to be reached for several years, and hopefully never.

Further up the River Murray, the Lake Bonney regulator is open and the lake is refilling. Lake Bonney will receive 25 gigalitres of inflow, which will fill the lake. The unregulated flow event provides an opportunity to top up Lake Bonney to pool level and reconnect it to the River Murray channel. I am advised that at this stage the estimated unregulated flows will not be sufficient to allow a full flushing of Lake Bonney, but it might provide the opportunity to open the structure indefinitely and help maintain a lower salinity level within the lake.

Higher river levels will also lead to the inundation of lower-lying areas of the flood plain and the watering of vegetation lining the river channel and wetlands, such as the river red gums. This environmental watering could potentially lead to breeding opportunities for fauna such as frogs and waterbirds. Water quality within connected wetlands will also improve. The unregulated flows will also allow the opportunity to open wetlands that were closed over the drought period to achieve evaporative savings.

This unregulated flow event is great news for South Australia and will provide significant environmental benefits for the River Murray environment in this state. It is important, however, that this good news event does not deflect attention from the need to address the long-term problems created by the overallocation of water in upstream states and the need for a whole-of-basin management plan to ensure we have a sustainable and healthy river system for the benefit of all South Australians in the future. In this context, I think we all eagerly await the release of the Murray-Darling Basin Plan Guide by the authority on 8 October.

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