On Wednesday the 16th of October the study tour visited the Warragamba Dam. First a presentation was given by Rusty, the educational officer who works for Water NSW (New South
Wales). Water NSW is the largest water supplier of New South Wales, providing two thirds of the water used in the state. Water NSW operates and maintains 42 dams of which the Warragamba dam is one of the largest. He then took us on a tour of the downstream side of the dam, also looking at the valves, transporting water to downstream water treatment plants. We than went through the dam looking at the maintenance tunnels trough the dam and lasers monitoring the dam. Lastly we went on top of the dam, looking at lake Burragorang and looking at the emergency spillway and gates.
Firstly, why was the dam build? Due to droughts and expanding population, the water demand of the Sydney area increased. The dam began operating in 1960 after 19 years of construction and potential being noticed from 1845. The record drought from 1934 till 1942 forced the development to ensure reliable water supply. In the meantime, the Warragamba emergency scheme was build to address the critical water shortage in New South Wales. This wear is still
present. The dam was build in series of large interlocking concrete blocks of 15m3 each. The Warragamba Dam is 142 meters high and 351 meters long. It’s thickness at base is 104 meters. Later an auxiliary spillways was added with a width of 190 meter and a length of 700 meter. The dam creates lake Burragorang. The area of the lake is 75km2 and has a length of 52 km. The total capacity of the lake is 2.031.000 ML with a maximum depth of 105 meter. It took 8 consecutive years to pour the concrete and 1500 people worked on the construction. To control the heat generation caused by the concrete mixing, potentially causing creaks, ice was used to
cool the process down for which an ice making plant was build in the vicinity.
The Warragamba Dam supplies water to three water filtration plants trough pipes using gravity. To ensure the water supply for people living in Sydney. To ensure the water quality is of sufficient quality, the water can be extracted from valves at different heights in the dam to ensure optimal quality is extracted. The water quality is measured at intervals at different water depths over the entire stretch of the lake. This creates a water quality profile which is used to determine which valve will release the best quality of water.
The biggest treats to the water supply are droughts, mining and bush fires. Continuous droughts have caused the reservoir to be almost empty at the beginning of the century. Therefore the lower lying valve was opened up. This needs a pump station and has a lower capacity than the normally used pipes. The mining industry poses another threat by releasing heavy metals into the reservoir. The strong political position of the mining industry makes it difficult to hold them accountable for the damages done. Next to the heavy metals, the mining activity’s cause leaks in the river bed which spills water form the reservoir. During operation a water bill is send to the companies but after the closing of the mine, this is not possible anymore. Lastly, a large bushfire in the catchment of the reservoir caused the water quality to drop significantly, causing the water being unusable for 2 years due to the large amount of particles in the water.
Recent floods, which have been more extreme due to climate change in recent years, pose a substantial threat to the residents of Sydney living downstream of the dam. To prevent
overtopping, in 1999 the construction of the auxiliary spillway was started. However, opening up the original spillways all ready causes flooding of residential areas downstream. Because the biggest existential crisis to Sydney is floods, heightening the dam is recommended by engineers
to provide emergency water storage capacity in case of heavy rain. However, storing additional water in the reservoir would cause flooding in protected area with cultural and aboriginal heritage sites. This would delay or prevent flooding downstream, proving residents with time to evacuate
reducing grid lock. Due to temperature changes, the material of the dam shrinks and expands, causing leakage and
movement of the dam. This is monitored by sensitive seismic equipment inside the dam. Water pressure, seepage and any physical changes to the dam structure and its foundations are
monitored trough a network of more than 5 km of galeries, to ensure these are within acceptable limits.
Since the dam has been in use. The water demand from customers has decreased significantly despite an increase of inhabitants in the greater Sydney area. This is due to education on water usage.