Designed by the State Rivers and Water Supply Commission of Victoria, construction of the original water storage, which was known as Sugarloaf Reservoir, took place between 1915 and 1929 to provide irrigation water for what was a vast uncultivated area on Victoria's northern plains. The dam was modified in 1929, and again in 1935 to increase the storage capacity to. However, this reservoir was still limited in its capacity to meet the growing demand for water in the Goulburn Valley and to protect farmers during drought years. Following a detailed feasibility study of all possible storage sites on the Goulburn River, it was decided that the existing dam site was the most suitable for construction of a larger dam. In 1951, work began to enlarge the storage to its present capacity. The enlargement was completed in 1955 and the storage was renamed Lake Eildon. The embankment dam wall is constructed with an earth core and rock fill, rising to a height of. The core component materials of the wall include of rock and earth. With a catchment area of that includes the Goulburn, Delatite, Howqua, Big, and Jamieson rivers and several minor tributaries, the reservoir covers an area of. The reservoir has a capacity of with an average depth of, and can release a maximum outflow of approximately via its controlled spillway. The crest of the uncontrolled spillway is and is approximately long. Lake Eildon is connected to the metropolitan water supply of Melbourne, the state capital, via a pipeline from the Goulburn River. On average, 91% of the water from Lake Eildon goes to the Goulburn Weir and the Waranga Basin before it flows to irrigators in the Goulburn Valley system.
Power generation
Operated byAGL Energy, Eildon Hydroelectric Power Station is a hydroelectric power station that operates during the irrigation season from August to May; its operation is mainly governed by release of water to meet irrigation demands, but it may also be operated during winter and spring when flood releases can be used to generate electricity. The power station can also be used to meet short term emergency power needs resulting from industrial disputes or plant breakdown elsewhere in the State's power grid. Initially completed as part of the Sugarloaf Reservoir with just of hydroelectric generating power, capacity was increased by 1957 to through the installation of two turbines. The first turbine was commissioned in 1956, and a second in 1957. In addition, there are two turbines; these were decommissioned in 1971, but recommissioned in 2001. These smaller turbines were relocated from the former Sugarloaf Power Station on the Eildon Weir, completed in 1929 and in use until work on the larger dam started in 1951. This renovation of the oldest turbines in 2001 led to a generation capacity of. A pondage below the dam temporarily detains water discharged from the power station and regulates releases downstream to minimise variations in flow due to intermittent power generation. In 1995 the Eildon Pondage Power Station, a small hydro-electric station with output was installed on the pondage. Eildon Power Station has four turbo generators, with a total generating capacity of of electricity. It produces an average of around of electricity per annum.
Houseboats
Lake Eildon has a thriving Houseboat culture. There is a Public Harbor and a Private Harbor. Rental of houseboats is possible in the Public Harbor, some boats are restricted to day time operation due to lack of lighting. The Private Harbor is manages the owners houseboats with staff and facilities that cater to over 18 marina's containing over 200 houseboats. Both harbors provide fueling facilities.
Drought and recovery
During the drought years in Victoria in the 2000s, Lake Eildon rarely filled and the once-thriving holiday destinations around the lake were unable to attract visitors, leading to considerable economic hardship. Although water is in great demand for agriculture, careful regulation has kept outflows fairly static. During November 2006 the lake dropped to a low of only 15% from the previous year level of 48.3%. After many years with below average rainfall, 2010 saw Lake Eildon receive above average rainfall and rose from 23% of capacity in May 2010 to be 82.5% as of March 2011.
