Lake Somerset

Somerset Dam
Wall of Somerset Dam
Location of the Somerset Dam in Queensland
Country	Australia
Location	South East Queensland
Coordinates	27°6′52″S 152°33′25″E / 27.11444°S 152.55694°E / -27.11444; 152.55694Coordinates: 27°6′52″S 152°33′25″E / 27.11444°S 152.55694°E / -27.11444; 152.55694
Purpose	Potable water supply Flood mitigation Recreation Hydroelectricity
Status	Operational
Construction began	1935 (1935)
Opening date	1959 (1959)
Operator(s)	SEQ Water
Dam and spillways
Type of dam	Gravity dam
Impounds	Stanley River
Height	50 m (160 ft)
Length	305 m (1,001 ft)
Width (base)	41 m (135 ft)
Dam volume	203×10^3 m3 (7.2×10^6 cu ft)
Spillway type	Gated
Spillway capacity	4,650 m3/s (164,000 cu ft/s)
Reservoir
Creates	Lake Somerset
Total capacity	904,000 ML (199×10^9 imp gal; 239×10^9 US gal)
Active capacity	380,000 ML (84×10^9 imp gal; 100×10^9 US gal)
Inactive capacity	524,000 ML (115×10^9 imp gal; 138×10^9 US gal)
Catchment area	1,330 km2 (510 sq mi)
Surface area	4,350 ha (10,700 acres)
Maximum length	52 m (171 ft)
Maximum width	7 m (23 ft)
Normal elevation	108 m (354 ft) AHD
Power station
Name	Somerset Dam
Commission date	1959 (1959)
Installed capacity	3.2 MW (4,300 hp)
Annual generation	12 GWh (43 TJ)
Website www.seqwater.com.au

The Somerset Dam is a mass concrete gravity dam with a gated spillway across the Stanley River that is located in the South East region of Queensland, Australia. The main purpose of the dam is the supply of potable water for the Brisbane, Gold Coast and Logan City regions. Additionally, the dam provides for flood mitigation, recreation and for the generation of hydroelectricity. The impounded reservoir is called Lake Somerset.

The dam, lake and surrounding village of Somerset are named in honour of Henry Plantagenet Somerset, a local grazier and Member of the Legislative Assembly of Queensland who represented the seat of Stanley from 1904 until 1920.

The dam is located approximately 115 kilometres (71 mi) northwest of Brisbane in the Somerset Region and 80 kilometres (50 mi) north of Ipswich.

The concrete dam structure is 50 metres (160 ft) high and 305 metres (1,001 ft) long. The 203-thousand-cubic-metre (7.2×10^⁶ cu ft) dam wall holds back the 904,000-megalitre (199×10^⁹ imp gal; 239×10^⁹ US gal) reservoir when at full capacity. However, only 380,000 megalitres (84×10^⁹ imp gal; 100×10^⁹ US gal) is used for water supply and the remainder used for flood mitigation. From a catchment area of 1,330 square kilometres (510 sq mi) that includes much of the western slopes of the D'Aguilar National Park, the dam creates Lake Somerset at an elevation of 108 m (354 ft) above sea level, with a surface area of 4,350 hectares (10,700 acres). The gated spillway has a discharge capacity of 4,650 cubic metres per second (164,000 cu ft/s). Built under the supervision of the Bureau of Industry, management of the dam was transferred to SEQ Water in July 2008 as part of a water security project in the South East Queensland region, known as the South East Queensland Water Grid. A small 4 megawatts (5,400 hp) hydroelectric power station is located adjacent to the dam wall.