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 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 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, 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 HunterRiver 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.
Access and recreation
The dam is a popular day trip destination for both locals and tourists 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.
