Significant water events
Widespread, heavy and persistent rainfall was recorded across southeast Australia between 27 February and 5 March 2012 as a result of a slow-moving low pressure trough and associated cloud band. The main significant feature of this event was the persistence of heavy rainfall over the course of a week, with some areas recording 50 mm or more on several days. Most of inland southeast Australia recorded accumulated rainfall totals in excess of 100 mm, with large areas recording totals in excess of 200 mm for the event. February and early March are seasonally dry in these areas, and the accumulated rainfall totals were several times the monthly average for the whole of February.
Canberra region received more than 200mm rainfall during March 2012, which was well above its long-term average rainfall (about 70mm) in March. Minor to moderate flooding occurred within the Canberra region in March 2012, which considerably affected the community around Queanbeyan and required the evacuation. (Bureau of Meteorology, Special Climate Statement 39).
The Murrumbidgee is the major river system that flows through the Canberra region within the Murray–Darling Basin, with all rivers and creeks in the Canberra region draining into the Murrumbidgee River.
For the 2011–12 year most of the Canberra region saw very much above average rainfall; this is reflected in Figures W1, W2 and W3, which each have flow rates well above the long-term average.
Figure W1 Monthly flow of the Molonglo River at flow gauging station 410705
There are three key water storages located on the Cotter River; the Corin, Bendora and Cotter reservoirs. They supply urban water for the Canberra region. Figure W2 shows flows down the Cotter River at gauge 410730 located upstream of the Corin Reservoir. These flows enter the Corin Reservoir where water released or spilled flows downstream to the Bendora Reservoir and eventually to the Cotter Reservoir.
Figure W2 Monthly flow of the Cotter River at flow gauging station 410730
The Queanbeyan River is a tributary of the Murrumbidgee River, and significant in the context of the Canberra region because the Googong Reservoir is located on it, southeast of Queanbeyan. High inflows into the Googong catchment saw increased streamflows and runoff into storage in the 2011–12 year.
Figure W3 Monthly flow of the Queanbeyan River at flow gauging station 410781
Major water initiatives
On 17 May 2011 the Environment and Sustainable Development Directorate (ESDD) was formed. ESDD delivers services and policy in the areas of climate change, waste, heritage, planning policy (including transport planning), and development, natural resource management, energy and water.
Following the Water Security Review in 2007, the ACT Government announced a range of new water supply projects, that ACTEW Water continued to implement throughout the 2011–12 year.
- Enlarging Cotter Reservoir to increase the capacity to 78,000 ML: Construction of this project commenced late 2009 and was expected to be completed in 2012 but significant rain events and flooding in 2012 have delayed construction
- The Murrumbidgee to Googong water transfer pipeline: This will allow the transfer of water from the Murrumbidgee River to Burra Creek, where it will flow into Googong Reservoir. Planning for this transfer continued during the 2010–11 year and construction commenced in early 2011. The Murrumbidgee to Googong water transfer was completed in August 2012.
- ACTEW Water have purchased 4.145 GL of high security and 12.523 GL of general security NSW water entitlements to be utilised under the Tantangara transfer. This is expected to be available for use upon the completion of the Googong transfer pipeline.
- In October 2007, the ACT Government announced a range of new water supply projects for the ACT region, including the design of a Demonstration Water Purification Plant. ACTEW Water completed the design, but construction has been deferred subject to the successful implementation of the other three water security projects (Enlarged Cotter Dam, Murrumbidgee to Googong Water, Transfer and Tantangara Transfer). ACTEW Water will continue to monitor water storage levels, rainfall and inflows to determine whether water purification is required to help secure our future water supply.
The Water Sharing Plan for the NSW Murray–Darling Basin Fractured Rock Groundwater Sources commenced on 16 January 2012. This water sharing plan is due for extension/replacement in July 2022. In 2020 when the Peel Valley Water Sharing Plan is due for remake, and in 2012 when the North Western NSW Water Sharing Plan is due for revision, the fractured rock groundwater sources within these plans will be merged with this plan. This would result in a single water sharing plan covering the inland fractured rock groundwater sources.
On 8 October 2010, the Murray–Darling Basin Authority published the Guide to the Proposed Basin Plan. Volume 1 of this suite of publications outlined the basis of the draft basin plan; Volume 2 specified the technical details were in parts 1–3. The draft basin plan was released for public comment in November 2011. It is expected the Murray–Darling Basin Plan will begin to be implemented from the end of 2012.
One of the key elements of the Guide to the Proposed Basin Plan is the setting of new limits, sustainable diversion limits, or SDLs, on the amount of water used in the basin. Sustainable diversion limits will be enforced through state water resource plans and fractured rock groundwater sources.