Serpentine Dam (Western Australia)

Dam in Western Australia

The Serpentine Dam is a major water supply dam for Perth, Western Australia. The dam is used to store water that is released at a controlled rate to regulate the level in the Serpentine Pipehead Dam reservoir, which in turn feeds water to the metropolitan trunk main network depending on demand. Construction of the dam was completed in 1961. The Serpentine Dam is one of the 15 dams, some of which have since been decommissioned, that have been built in Western Australia since the 1920s, along with the Serpentine Pipehead Dam. It was built as part of the Integrated Water Supply System (IWSS), the largest scheme currently managed by the Water Corporation, which provides water for over two million people in Perth, Mandurah, and other Western Australian regions. Serpentine Dam is connected to the Serpentine Pipehead Dam, which stores water and desalinated water from the Serpentine Dam and other dams nearby for later use. The Serpentine Dam is an important water source because the Perth metropolitan area depends on it as a strategic water source, supplying on average per year, with an additional from the natural flows into the Serpentine Pipehead Dam. With these limited resources, water shortages occurred and the existing water sources became polluted over time. This caused the rapid spread of diseases such as typhoid and diphtheria, especially among less fortunate people, and many became sick.

The Serpentine Dam catchment is situated in the Darling Plateau within the Darling Scarp, on Kingsbury Drive, around south of Jarrahdale, Western Australia. According to the Water Corporation, the Serpentine Dam can hold up to of water, has a wall height of at the lowest foundation and a reservoir length of The catchment has an area of The reservoir is at Australian Height Datum (AHD) and the highest point of the catchment, Mount Cuthbert is at AHD on the catchment’s east boundary, based on the Serpentine Dam Catchment Area Drinking Water Source Protection Plan (2007). In 2011, "water supplies in Perth and the South West reached critically low levels after almost a year with no significant rain."

Most of the dam catchments that are connected to the IWSS are located in the south western area of Western Australia. Alcoa has mined in these catchments to obtain bauxite ore since 1963. The mining has significantly affected the northern Jarrah forest, including the Serpentine catchment as the mining process requires clearing forests, soil stripping in two layers, blasting of lateritic duricrust and finally removal of broken duricrust with the underlying friable bauxite. The lost forest area is estimated to be replaced by 2032 as they have started to replant the lost forest area throughout the years with a prescription of 1300 tree stems per Consequently annual inflow to the Serpentine Dam was projected to increase by 3.5% in 2011–2030, but decrease overall by 4.5% in 2030–2050.

Pathogens are always a threat to water supply sources since they pose as a significant risk to public health, its effects on people range from illness up to even death, so water treatment regularly occurs in the Serpentine Dam catchment. Water treatment in the catchment can be directly affected by the land use activities that occur in and around the area. For example, off road driving on unauthorised tracks contribute to erosion in the area. Erosion affects the soil particles within the catchment and causes them to increase the turbidity in the air. In turn, existing pathogens can adsorb these soil particles and can potentially resist disinfection better, thus increasing the risk of contamination of the water in the catchment. Other effects include the uprooting of vegetation, affecting plant growth, and smothering of riparian vegetation.

There is approximately of private land in the south east edge of the Serpentine Dam catchment. This private land is used for Tasmanian bluegum (Eucalyptus globulus) plantations, private dams, and some pasture and remnant native vegetation. In 2007, a large chunk of this land was sold to a Boddington Gold Mine (BGM) venture that planned to expand gold mines near Boddington disturbing the State Forest around the area. To get around this issue, BGM traded with the Department of Environment and Conservation other plots of land that had a similar size and conservation value to make up for the State Forest that would be disturbed from the BGM expansion project. This land eventually became Crown Land that would be managed by the Department of Environment and Conservation (Western Australia).

The Serpentine Dam catchment lies within State Forests Number 14 and 67. The State Forests are managed by the Department of Environment and Conservation and currently used for nature conservation, recreation, timber production, and has many other purposes. Bauxite mining is also conducted in a part of the Crown Land in the catchment, the area in which the bauxite mining is done is planned to expand in the future. of the Crown Land is used for Frollett pine plantation in the north side of the catchment. The plantation is harvested when the time is right. Other uses for the Crown Land include the Albany Highway passing through the Serpentine catchment, and the Muja Northern Terminal Line, a major Western Power transmission line. also passes through the Serpentine catchment. The Serpentine National Park is considered part of the catchment, being part of two thirds of the Serpentine Pipehead Dam catchment.

Recreation in the State forest and National Parks is managed by the Department of Environment and Conservation. The catchment has numerous recreation activities like hiking, which happens throughout the catchment, specifically along the Bibbulmun Track which passes through the catchment around upstream of the Serpentine Dam. The area is home to the Monadnocks Campsite and the White Horse Hills Campsite. Other approved significant recreational activities include orienteering, rogaining, picnicking, and mountain biking. The Munda Biddi Mountain Bike Trail passes through the north of the Serpentine Dam catchment area. The Water Corporation operates a picnic area directly downstream of the Serpentine Dam catchment area. The Western Australian Endurance Riders Association (WAERA) have held annual horse riding events in the north west side of the catchment. The Darling 200 Rally run by the Light Car Club of WA Inc. under Motorsport Australia, previously known as the Confederation of Australian Motor Sport (CAMS) also used to regularly hold established motor events in the spring in the Serpentine catchment. Unauthorised activities include swimming, boating, and fishing.

The Serpentine Dam is intended to go on supplying the Perth metropolitan area and other regions in Western Australia with drinking water. With the varying seasons and likelihood of drier years into the future from rainfall reduction due to climate change, and as demand increases, the government of Western Australia, along with landholders will need to consider developing additional water sources on top of the current existing IWSS dams to meet future water demands.