Warragamba Dam

Infobox_lake
lake_name = Warragamba Dam
image_lake = Warragamba_Dam.jpg
caption_lake = Warragamba Dam Wall
image_bathymetry =
caption_bathymetry =
location = 60km West of Sydney, Australia
coords = coord|33.8834|S|150.596|E|type:waterbody_region:AU
type = reservoir
inflow = Coxs, Kowmung, Nattai, Wingecarribee, and Wollondilly Rivers
outflow = Warragamba River
catchment = 9051 km²
basin_countries = Australia
length =
width =
area = 75 km²
depth =
max-depth = 105 m
volume = 2,031,000 ML
residence_time =
shore = 354 km
elevation =
islands =
cities =

Warragamba Dam is Sydney's primary water source. It is approximately 65 km to the west of Sydney on the Warragamba River.

Overview [The Water Supply, Sewerage and Drainage of Sydney, W.V.Aird, 1961, MWS&DB.]

The Warragamba River flows through a 300-600 m wide and 100 m deep gorge that opens out, at the upper end, into a large valley, the Burragorang Valley. This river configuration allows a relatively short but high dam wall in the gorge to impound a vast quantity of water.

In 1845, Paweł Edmund Strzelecki drew attention to Warragamba River as a water supply catchment. In 1867, supporters proposed a dam. Between 1867 and 1946, supporters proposed various schemes before the site and design of the current dam received approval. In 1940, a weir and pumping station known as the Warragamba Emergency Scheme reached completion, just downstream of the main dam site.

In 1943 the Metropolitan Water, Sewerage and Drainage Board invited the geologist William Rowan Browne to investigate a proposed site. Browne found a more suitable site and continued as geological adviser until completion. [ [http://www.adb.online.anu.edu.au/biogs/A130317b.htm Browne, William Rowan (1884 - 1975)] , Australian Dictionary of Biography]

Dam construction began in 1948 and completed in 1960. The resulting dam of the Warragamba River formed Lake Burragorang, which is one of the largest reservoirs for urban water supply in the world. There is also a hydroelectric power station at the dam that can generate 50 MW.

The dam wall comprises 3,000,000 tonnes (1 200 000 m³) of concrete. It is so large that the engineers had to use two techniques to stop the temperature becoming too hot as the concrete set. One was to add ice to the wet concrete, which was the first application of this technique in Australia. The other was to embed cooling pipes into the concrete and circulate chilled water through the pipes.

Following a 1987 and 1989 re-evaluation of the potential rainfall and flood risks, the government raised the dam wall by 5 m and constructed an auxiliary spillway on the east bank of the dam.

In 2006, the Warragamba Deep Water Storage Recovery Project, part of the NSW Government’s Metropolitan Water Plan, penetrated the base of the dam wall to allow the previously inaccessible lowest water in the reservoir to be available. This new outlet was below the minimum level required for gravity flow, which delivered water from the existing outlets. So, the project constructed a new pumping station downstream of the dam. The new pumping station is within the Emergency Scheme pumping station chamber. This project provided access to 8% more water or approximately six months of extra supply. On 15 April 2006, the project reached a major milestone when it increased the available storage from 1,857,000 Megalitres to 2,027,000 Megalitres. A similar scheme is currently underway at Nepean Dam.

Other recent major work includes a complete upgrade of the three passenger lifts within the dam wall, an upgrade of the traveling crest crane and a complete upgrade of the four water supply outlets in the valve house, which includes the replacement of the major valves. A full electrical upgrade is currently in advanced planning stage, as is a mechanical upgrade that will address the drum gate and four radial gates.

Although the engineers did not design Warragamba Dam as a flood control measure, it can mitigate flooding by holding floodwaters back while the reservoir fills.

Warragamba Dam was also a popular picnic spot for Sydneysiders, with up to 3000 people visiting the area on a typical Father's Day, however the dam is now closed to public access.

Water levels

As of May 2008 Warragamba Dam is over 60% full. Warragamba Dam is one of the fullest dams in Australia and New South Wales.

Catchment

The catchment area is 9050 square kilometres. The areas closest to the lake, making up around 30% of the total catchment, are restricted access special areas. Most of the rest of the catchment consists of cleared farming land and contains large and small towns, which discharge treated sewage into the catchment.

Dam Level Crises and Water Restrictions

There have been times when drought has seriously depleted the dam. In March 1983, Lake Burragorang's level reached a low of 45.4% of capacity. Between 1998 and 2007 the catchment area experienced extremely low rainfall, and on 8 Feb 2007 it recorded an all time low of 32.5% of capacity [ [http://www.sca.nsw.gov.au/dams-and-water/weekly-storage-and-supply-reports/2007/bulk-water-storage-and-supply-report-08-february-2007 Sydney Catchment Authority - Bulk Water Storage & Supply Report 8 Feb 2007] ] . If Sydney's water supply runs out it would be a major economic disaster so the New South Wales State Government tries to reduce this risk by implementing water restrictions. [ [http://www.sydneywater.com.au/SavingWater/WaterRestrictions/ Sydney Water - Mandatory Water Restrictions] ] Heavy rains between June 2007 and February 2008 restored the dam level to around 67%, but Level 3 water restrictions remain in place.

Dam statistics

* Height: 142 m
* Length: 351 m
* Thickness at top: 8.5 m
* Thickness at base: 104 m
* Width of central spillway: 94.5 m
* Width of auxiliary spillway (at mouth): 190 m
* Length of auxiliary spillway: 700 m
* Hydro-electric plant capacity: 50 MW

Lake Burragorang statistics

* Available storage (when full): 2,027,000 ML (note: the lowest depths have recently become available for supply)
* Total capacity (when full): 2,031,000 ML
* Surface area: 75 km²
* Length of lake: 52 km
* Length of foreshores: 354 km
* Deepest point: 105 m
* Catchment area: 9051 km²
* Average annual rainfall: 840 mm

See also

* 1998 Sydney water crisis
* Warragamba - township originally built to house dam builders.The Hawkesbury River

External links

* [http://www.sca.nsw.gov.au/dams/warragamba.html Sydney Catchment Authority - Warragamba Dam]
* [http://www.floodsafe.nsw.gov.au/faq_warragamba.html FloodSafe NSW Warragamba FAQ]
* [http://www.iliveinsydney.com/water/damstats.php Sydney's Dam Levels - current statistics and graphs]

References