Karangi Dam
Coffs Harbour Water publishes details about the water capacity in Karangi Dam on a weekly basis.
Dam capacity for week ending 22 6 09 (70KB)
For further information contact Coffs Harbour Water on (02) 6648 4000.
HISTORY
Karangi Dam was built in 1980 to service the residents of Coffs Harbour, Sawtell and the coastal strip north of Coffs Harbour, including Woolgoolga.
It was originally designed to store 2200 megalitres of water pumped from Cochranes Pool on the Orara River.
Due to a growing population and water demand in this region, in 1988, the Department of Public Works & Services raised the dam by adding a 1.5 metre high Labyrinth Weir to the existing spillway & an extra 1 metre to the top of the dam. This increased the capacity to 2630 megalitres.
After many years of water restrictions it was decided to raise Karangi Dam a further 10 metres in 1994, as an emergency measure, until a Regional Water Supply Scheme was finalised. Raising the dam increased the capacity to 5600 megalitres.
The purpose of the dam is to store sufficient water so that:
- During high flow periods the dam is filled from the Orara River.
- In dry periods, when there is low flow in the Orara River, water will be supplied from the dam. This is to protect the river ecology.
- When the Orara River water becomes excessively dirty (turbid), during flood times, water need not be pumped.
Dam construction details:
Item | Original Dam | After Labyrinth Wall | After Raising 10 metres |
|---|---|---|---|
| Catchment Area | 138 Hectares | 138 Hectares | 138 Hectares |
| Storage Area | 21.6 Hectares | 24 Hectares | 34 Hectares |
| Core Material | 400.000 m3 | 405,000 m3 | 455,500 m3 |
Downstream Earth Fill | Nil | Nil | 202,000 m3 |
| Fine Filter Material | 20,000 m3 | 20,000 m3 | 30,350 m3 |
| Course Filter Material | 12,000 m3 | 13,000 m3 | 21,800 m3 |
| Rock Fill | 10,000 m3 | 12,000 m3 | 82,200 m3 |
| Total Embankment Volume | 442,000 m3 | 450,000 m3 | 792,000 m3 |
| Crest Length | 300 metres | 320 metres | 540 metres |
| Crest Width | 7 metres | 5 metres | 7 metres |
| Maximum Base Width | 175 metres | 175 metres | 220 metres |
| Maximum Wall Height | 38 metres | 39 metres | 49 metres |
| Upstream Slope | 1:3 | 1:3 | 1:3 & 1:2.4 |
| Downstream Slope | 1:2 | 1:2 | 1:2 & 1:1.5 |
| Total Cost | $2.4 million | $2.8 million | 11.0 million |
