The Wivenhoe and Somerset Dams Optimisation Study (WSDOS) (PDF, 10.3MB) presents a range of options for the management of the Wivenhoe and Somerset dams during a flood event.
This study was completed in response to recommendations of the Queensland Flood Commission of Inquiry's final report.
After seeking community feedback on the options in the WSDOS report, the Queensland Government has selected the option known as 'Alternative Urban 3' as its policy for the optimised operational strategy for the dams during floods.
The optimised operational strategy changes how the flood mitigation compartment of Wivenhoe Dam is used, allocating more space to protect houses and buildings from damage during a large flood and potentially delivers a 5 to 10 per cent reduction in flooding during a major flood.
The optimised operational strategy will be incorporated into the Manual of Operational Procedures for Flood Mitigation at Wivenhoe Dam and Somerset Dam.
Details of the community consultation can be found in the consultation report (PDF, 391.2KB).
The discussion paper (PDF, 638.5KB) provides an overview of the study as well as the preferred option. It should be used as a guide to understanding the WSDOS Report. This paper was utilised in a comprehensive three month consultation period, which occurred from April to June 2014.
The Department of Energy and Water Supply and Seqwater won the Premier's Award for Excellence in the Integrity and Accountability category in December 2014.
The joint nomination highlighted the complex strategies developed to better protect Brisbane and Ipswich homes and businesses in the event of a large flood event.
The Wivenhoe and Somerset dams are dual purpose water supply and flood mitigation dams. They are key infrastructure for our water supply and provide flood mitigation to communities downstream including Brisbane and Ipswich.
Wivenhoe Dam is one of the largest storages in Queensland. The dam catchment receives approximately 1,000 mm of rainfall annually, mostly occurring in summer. It has a full supply volume of 1,165,000 megalitres for urban water use (including drinking water), and an additional temporary flood storage of approximately 1,835,000 megalitres.
Somerset Dam drains into Wivenhoe Dam and is operated concurrently during floods to maximise the flood mitigation benefits downstream of Wivenhoe Dam. Somerset Dam has a full supply volume of 380,000 megalitres for urban water use (including drinking water), and an additional temporary flood storage of approximately 524,000 megalitres.
The Brisbane River catchment has an area of about 15,000 km2 extending from Moreton Bay to the Great Dividing Range. This catchment includes the major sub-catchments of the Upper Brisbane, Stanley and Bremer rivers and Lockyer Creek. Average annual rainfall ranges from 1,700 mm at Peachester above Somerset Dam to 730 mm at Cooyar near the western boundary.