| Lake Manchester Dam | |
| Location Map: | Queensland |
| Location Map Caption: | Location of the Lake Manchester Dam in Queensland |
| Coordinates: | -27.4881°N 152.7514°W |
| Country: | Australia |
| Location: | South East Queensland |
| Status: | O |
| Operator: | SEQ Water |
| Dam Type: | G |
| Dam Height: | 43.8m (143.7feet) |
| Dam Length: | 188m (617feet) |
| Dam Volume: | 45e3m3 |
| Dam Crosses: | Cabbage Tree Creek |
| Spillway Type: | Uncontrolled |
| Spillway Capacity: | 450m3/s |
| Res Name: | Lake Manchester |
| Res Capacity Total: | 26217ML[1] |
| Res Catchment: | 74km2 |
| Res Surface: | 264ha |
Lake Manchester Dam is a concrete gravity dam with an un-gated spillway across Cabbage Tree Creek. It is also known as Cabbage Tree Creek Dam.[2] It is in the locality of Lake Manchester, City of Brisbane, Queensland, Australia. The main purpose of the dam is for potable water supply of Brisbane.[3] The impounded reservoir is called Lake Manchester.
The dam is located in the area surrounding the suburb of the same name, approximately north of . The primary inflow of the reservoir is Cabbage Tree Creek, not far above its confluence with the Brisbane River to the south-west of the dam .[4] Its original purpose was to supplement supplies when the flow of the Brisbane River was low. Today it is one of a number of dams connected to the South East Queensland Water Grid.
The concrete dam structure is high and long. The 45e3m3 dam wall holds back the 26217ML reservoir when at full capacity. From a catchment area of that includes much of the western slopes of the D'Aguilar Range, the dam creates Lake Manchester, with a surface area of . The uncontrolled un-gated spillway has a discharge capacity of .[3] Initially managed by the Metropolitan Water Supply and Sewerage Board, and then the Brisbane City Council, management of the dam was transferred to Seqwater in July 2008.
The Enoggera Dam, the Gold Creek Dam and the Mount Crosby Weir were built to supply water to Brisbane but could not meet growing demand. A site upstream from the creek's confluence with the Brisbane River was selected as this was the next catchment to the west in the D'Aguilar Range. The designer was Allan Hazen, an American engineer. Construction of the Lake Manchester Dam commenced in 1912 and when it was completed in 1916, it was the fourtholdest dam in Queensland[3] and was originally called the Cabbage Tree Creek Dam. The dam was renamed in 1916 in honour of E. J. T. Manchester, the president of the Metropolitan Water Supply and Sewerage Board.[5] In 1924 the elevation of the bywash was raised which added to the dam's capacity.[5]
In October 2005 the dam was reactivated as drought reduced the region's water supply to a critical point. The same year a report claimed that due to leaks and cracks the structure could break in a severe rain storm event.[6] In 2007 the dam's capacity was again raised and connection to the regional water grid was re-established. The Lake Manchester Dam Flood Security Upgrade was a Brisbane City Council project to ensure that the dam met the Australian National Committee on Large Dams (ANCOLD) guidelines for large dams.[7] The project involved strengthening and raising the dam wall for flood security purposes. Work began in early 2007[7] and was completed in 2008.[1]
Recreational activities which are permitted around the dam include barbecuing, camping, horse riding, mountain biking, picnicking and bushwalking.[1]