Mangrove Creek Dam, a concrete faced rockfill embankment

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

, is the primary

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

for

water supply Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Thes ...

to residents of the Central Coast in

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, Australia. The dam, with a capacity of and fed by a catchment area of , is operated by the Central Coast Water Corporation and supplies approximately 93 per cent of water to residents in Central Coast Council. The dam was constructed between 1978 and 1982, formed by impounding the headwaters of Mangrove Creek, a tributary of the

Hawkesbury River The Hawkesbury River, or Hawkesbury-Nepean River, is a river located northwest of Sydney, New South Wales, Australia. The Hawkesbury River and its associated main tributary, the Nepean River, almost encircle the metropolitan region of Sydney. ...

Dam and spillway statistics

The concrete faced rockfill embankment dam was built due to a rising demand for water from the expanding population on the Central Coast. The dam was built to boost water supply storage and to help provide a more reliable water supply. Mangrove Creek Dam was built using rolled, soft rockfill of

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) b ...

and siltstones. This material was obtained from a quarry located within the storage area. These sandstones and siltstones were crushed and compacted to form the dam embankment. The embankment also contains approximately of processed basalt. This material was incorporated into various filters and drains within the embankment to cope with seepage within the embankment and foundations. The concrete face which tapers from at the base to at the crest acts as a seal between the water and the dam embankment. Provision was made to increase the height of the dam wall by to a total capacity of if the need arose in the future. The height of the dam wall is , with a length of . The dam

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...

is a concrete lined chute of approximately with a width that tapers from to , with the capacity to discharge a water flow of into the impounded Mangrove Creek. During 1989, the Boomerang Creek Tunnel was completed. This tunnel enabled water to be transferred from Mangrove Creek Dam to Wyong River, for extraction at the Wyong River Weir for storage in Mardi Dam. This water was then extracted downstream at Lower Wyong River Weir and pumped for storage in Mardi Dam.

Catchment

Mangrove Creek Dam was proposed as a large storage dam, not primarily a collection dam. Its catchment area was relatively small but the shape of the valley and its geology enabled the construction of a relatively high wall that would store of water, reaching a maximum water depth in the reservoir of . When at full supply, the reservoir has a surface level of approximately , generated from the catchment area and annual average rainfall of .

Supply levels

Sustained low water conditions, including a 15-year

drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...

, took the level of water to 10.27% of total capacity during February 2007, following an earlier reading of 13.3% during January 2007. Local government officials immediately placed a range of water restrictions on residents and businesses in order to conserve water and ensure ongoing supply to the region's residents and tourism industry. Piping of water from the

Hunter River Hunter River may refer to: *Hunter River (New South Wales), Australia *Hunter River (Western Australia) *Hunter River, New Zealand *Hunter River (Prince Edward Island), Canada **Hunter River, Prince Edward Island, community on Hunter River, Canada ...

system augmented local water supply. In 2007, a water plan was established and detailed a program to expand supply and reduce demand to help secure the water supply until 2050. Between 2010 and 2012, a link was established between the Mangrove Creek Dam and Mardi Dam. This Mardi-Mangrove Link is made up of two pipelines that enable water to be transferred from the Wyong River and Ourimbah Creek, via Mardi Dam to the large Mangrove Creek Dam for storage, instead of allowing it to flow to the ocean. It is expected that this link will help protect the Central Coast region against future extended periods of below-average rainfall. In 2022, After days of heavy rainfall Mangrove Creek Dam reached 100% capacity and began spilling over the spillway for the first time since construction of the dam was completed in 1982.

Access and recreation

The dam is a popular

day trip A day trip is a visit to a tourist destination or visitor attraction from a person's home, hotel, or hostel in the morning, returning to the same lodging in the evening. The day trip is a form of recreational travel and leisure to a location tha ...

destination for both locals and

tourists Tourism is travel for pleasure or business; also the theory and practice of touring, the business of attracting, accommodating, and entertaining tourists, and the business of operating tours. The World Tourism Organization defines tourism mo ...

for barbecues and picnics, taking about 45 minutes to reach by car from Gosford. Restrictions apply on accessing the dam and the catchment area in order to protect water quality, protect large areas of bush land and plant and animal habitats, protect threatened plants and animal species, and preserve evidence of Aboriginal occupation.

References

External links