North Pine Dam
North Pine Dam’s preliminary function is to provide a safe water supply for Brisbane, Pine Rivers, Redcliffe and parts of Caboolture. The dam has a 348 square kilometre catchment area with an average annual rainfall of 1175mm. The dam stores 215,000 megalitres of water, which will ensure a continuous supply of 150 megalitres of water per day during the worst drought on record.
The normal water supply holding level is 39.63 metres above sea level. At this height a 2181-hectare lake is formed. Water is drawn from the dam through an outlet tower built on the face of the dam. Outlets, guarded by screens and valves, are provided at several depths so that the best quality can be taken from the reservoir and supplied to the treatment plant.
North Pine Dam is built across the North Pine River, 5 kilometres upstream from Petrie. The dam is built on a solid rock foundation made watertight by injecting cement grout at a high pressure into boreholes in the rock.
The central section of the dam is a mass concrete structure. This type of construction resists the thrust of the water by its weight alone. It has a central concrete spillway section on which five steel gates are installed.
The dam wall is 580 metres long and 40 metres high. To reduce costs, instead of using concrete, the shallow flanks of the dam wall were completed with rock and earth embankments. In addition to the main dam, there are three earth-filled embankments built across low ridges to the south-west of the dam. The largest of these is 8 metres high and they total 1000 metres in length.
The Department of Local Government carried out the design of the dam. The Coordinator General’s Department supervised the construction contracts. The dam was completed in 1976 at a cost of $20 million. Twenty-seven kilometres of road had to be relocated for the dam.
In 1996, an aeration system was installed in the Dam in an attempt to improve water quality through destratification of the lake. Destratification mixes the temperature-based layers of water in the lakes so that uniform temperatures are achieved over the depth of the Lake. The installation comprises two 75-kilowatt compressors, each delivering 200 litres of air per second through over two kilometres of submersed pipework.
North Pine Dam Flood Event - Feb 1999
The dam has a total storage capacity of 215,000 megalitres. As North Pine Dam is a water supply dam only, its flood compartment is negligible. The flood waters are discharged from the dam over the spillway which is located in the central concrete section of the dam. The spillway is normally closed by five steel gates but these are opened progressively during a flood in such a way to minimise the effects of flooding downstream.
Key Dam Statistics
This chart shows key features of Dams and Storages