Lake Somerset is an artificial lake created by the Somerset Dam on the Stanley River in South East Queensland. The dam was completed in 1953 and is the site of a small 4 MW hydroelectric power station. Somerset dam also provides flood mitigation and water storage for the city of Brisbane. The dam is managed by SEQ Water. A level of 90% is the optimum capacity for keeping evaporation rates to a minimum. Dam operators discharge water into the Wivenhoe Dam downstream to hold Somerset at this level when inflows are occurring.
At full capacity the lake holds 904,000 megalitres. Under normal conditions 380,000 megalitres is reserved for water supply, but the dam can hold another 524,000 megalitres to temporary store flood waters. The mass concrete gravity type dam wall is 305 metres long and contains 203,000 cubic metres of concrete. The dam contains 30 kms of navigable waterway and a permit is required to use watercraft on the lake.
Construction began in 1935. Worker's cottages had to be built and other facilities were constructed to attract 1000 construction workers and their families to the area. By 1942 the dam was almost complete when workers were diverted to the war effort. Work on the dam recommenced in 1948. Opened in 1953 when structural work was finished, it wasn't until 1958 that the dam was officially named after Henry Somerset and the next year before all work related to the dam, including the hydroelectric power station was complete.