Significant water events
The Sydney region was affected by a short-lived east coast low on the 8 March 2012. During this event, New South Wales experienced widespread and severe flooding with more than 75% of the State affected by flood warnings early in the month. Flash flooding occurred in the metropolitan region and the Hawkesbury–Nepean catchment experienced minor and moderate flooding.
The flood event of early March resulted in a large volume of water spilling from Warragamba Dam. Spilling began on Friday 2 March 2012 and the gates were closed on 24 March 2012. During this time a total of 633 GL of water was released from the storage. This was the first time that Warragamba Dam had spilled since 1998.
- Colo River at Upper Colo in the Hawkesbury–Nepean catchment
- Shoalhaven River at Fossickers Flat in the Shoalhaven catchment.
The two river locations were selected for the following reasons:
- long-term flow data are available
- flows upstream of both river locations are unregulated and diversions are negligible
- both are major rivers in terms of flow volumes.
Throughout the year the Shoalhaven River showed average to above average flows. Data for the months July, August and September was incomplete for the Colo River; but for the data that was available, the Colo River experienced below average flows. The Shoalhaven river experienced very much above average flows during March as a result of the high rainfall during that period. The Colo River situated to the north of the region was not impacted by this high rainfall during March, and only exhibited average flows. See the Climate overview for further details of climatic conditions experienced in the region during 2011–12.
Figure W1 Graph of total monthly flow along the Shoalhaven River during 2011-12 compared with long-term percentiles
Figure W2 Graph of total monthly flow along the Colo River during 2011–12 compared with long-term percentiles
Major water initiatives
Water sharing plans have been progressively developed for rivers and groundwater systems across New South Wales following the introduction of the Water Management Act 2000 (New South Wales).
Water sharing plans bring water users, still operating under the Water Act 1912 (New South Wales), into the one licensing system managed under the Water Management Act and sets the rules for how water is allocated over the next ten years.
Once a water sharing plan is approved, the New South Wales Office of Water may establish an implementation program under the Water Management Act for relevant areas.
The Water Sharing Plan for the Greater Metropolitan Region Unregulated River Water Sources and the Water Sharing Plan for the Greater Metropolitan Region groundwater sources both commenced on 1 July 2011 and can be accessed from the NoW website.
Lithgow Sewage Treatment Plant Augmentation
The plant augmentation has been designed to meet the needs of Lithgow for the next 30 year. There are two treatment plants on this site. The original plant is a traditional trickling filtration system which was designed and constructed in the mid 1980s to service Lithgow. The new plant is a modern activated sludge treatment system, known as Intermittent Decanted Extended Aeration (IDEA, see information below).
Wallerawang Sewage Treatment Plant Replacement
This plant is located within the catchment of Piper's Flat Creek (a protected waterway) and within the Sydney water supply catchment (Warragamba Dam). Lithgow City Council undertook extensive planning and consultation before deciding to replace the existing trickling filter plant with a new IDEA plant.
The plant has been designed to meet the needs of Wallerawang for the next 20 years.
IDEA treatment system
IDEA is a well-proven and economical treatment technology. Unlike older treatments, it is able to remove nitrogen as well as phosphorous – the two nutrients that, in combination, are responsible for potential algal blooms in receiving waterways. In addition it incorporates improved disinfection through chlorination, dechlorination and ultra-violet exposure. This provides an additional barrier to assure reduction of crytosporidium and giardia before discharge to the environment or use as recycled water.
For more information on sewage treatment in Lithgow City Council go to the Lithgow City Council website.
As a result of the completion of the Southern Highlands Pipeline on 24 September 2011, the Sydney Catchment Authority (SCA) will be able to supply water to Goulburn Mulwaree Council from Wingecarribee Reservoir in the Southern Highlands via an 88 kilometre pipeline from the reservoir to Goulburn. The pipeline is owned by Goulburn Mulwaree Council and has a maximum capacity of 5 megalitres per day.