Pejar Dam
Encyclopedia
Goulburn, New South Wales
Goulburn is a provincial city in the Southern Tablelands of New South Wales, Australia in Goulburn Mulwaree Council Local Government Area. It is located south-west of Sydney on the Hume Highway and above sea-level. On Census night 2006, Goulburn had a population of 20,127 people...
. It is one of three water storage facilities serving the city, and is used to augment the water supply when Sooley Dam is unable to maintain enough water in Rossi Weir, from which Goulburn's water filtration plant is supplied.
The dam was completed in 1980 by the New South Wales Department of Works for the Goulburn City Council to augment the water supply. It can store 9,000 megalitres
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
over 1.55 square kilometres collected from a catchment of 142 square kilometres. The dam wall is 25 metres high.
Water is released from the dam down the Wollondilly River
Wollondilly River
The Wollondilly River is a perennial river in New South Wales, Australia. It was originally a tributary of the Warragamba River, and hence of the Nepean and Hawkesbury Rivers...
where due to issues of loss the water fails to arrive at Rossi weir, upstream from Goulburn. Water is actually pumped to the city's water treatment works from Rossi Weir which is pumped down from Sooley Dam then and distributed to Goulburn's reticulation system for consumption.
In theory Pejar Dam represents 60% of Goulburns’ water, because of its size in proportion to the total storage. In practice Pejar Dam does not perform near this level because it is not catching and then delivering that amount of water to Goulburn. This is because Pejar Dam has no engineered link to the City and no engineered link to the river.
In March 2006, in the drought, Council released all the remaining water from Pejar (about 900ML or 10% of its storage) when Sooley Dam was full. This was a clear breach of the operating rules. Council figures show that over the period of this release from Pejar, the City experienced the largest amount of water lost from storage on record. About 600ML of water was unaccounted for, or about 4 months supply at that time. This is the equivalent of 70% of what was in Pejar, lost.
It has become evident from Councils’ 2007 hydrology studies, that Pejar Dam doesn’t yield as much water as it was originally estimated to yield, particularly in drought years. Pejar Dam was last full in November 2000. Five years later, in May 2006, it was empty. It remained empty until heavy, specific rain in June 2007. As of 2008, Pejar is about half full.
During this same period Sooley Dam did not drop below 70% of storage. Sooley obviously has a better yield than Pejar as a result of its catchment location and ability to draw flood water back form the river for storage. In addition Sooley Dams’ pipeline and short water transfer to Goulburn also contributes to its better supply performance.
In May 2005, the council of the city of Goulburn announced that storage had reached a crisis point as dam levels fell to 10% of capacity this was simply not true. Even though there had been no significant rain since December 2004 Sooley Dam had maintained a capacity of 70%. Despite this the council enforced the strictest of water restrictions, and released a political motivated statement that the city was likely to run out of water by early-2006....
The last time the dam was full was in November 2000 however as the water released from Pejar Dam cannot due to loss ever supply Sooley Dam the need for a pipeline is required.
In November 2005, although the drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
has broken in districts surrounding the region, the dam is still 11% full. By April 2006, this level has dropped to 0.1% of capacity.
On 21 April 2006 the Pejar Dam was declared officially empty after the local water authority emptied the Dam.
Michael McGill was the Resident Engineer on the Dam, he worked on behalf of the Department of Public Works.