The dam is a mix of a concrete gravity dam with four earth embankments. The dam wall height is and the crest is long with the auxiliary embankments extending a further. The maximum water depth is and at 100% capacity the dam wall holds back of water at AHD. The surface area of Lake Hume is and the catchment area is. The dam wall is constructed of rock covered with clay and other earth and is designed to carry vehicular traffic. A controlled concrete spillway that comprises a gated concrete overflow, with twenty-nine vertical undershot gates, is capable of discharging. Water is retained nearly upstream of the reservoir in the valleys of both the Murray and Mitta Mitta rivers. The dam wall was extended during the 1950s, and completed in 1961, necessitating the wholesale removal of Tallangatta township and its re-establishment at a new site west of the original, as well as railway and road diversions. Monitoring of the dam in the early 1990s revealed that the water pressure and leakage had caused the dam to move on its foundations slightly, leading to concerns that the dam was heading for collapse, threatening Albury-Wodonga and the entire Murray basin. Authorities denied any short-term threat. Traffic was banned from the spillway, and remedial work commenced involving, in part, the construction of a secondary earth wall behind the original to take the strain. Further upgrades to the dam at an estimated cost of 60 million commenced in 2010 and are due for completion in 2015. These works include the installation of an improved filter and drainage system on the junction between the concrete spillway and southern embankment, construction of a concrete buttress on the southern training wall, and possible modifications to improve the ability of the dam to manage extreme floods.
Power station
The Hume Power Station is a hydro-electric power station installed in the dam wall, and is primarily used for peak-load generation. The station has an average annual output of. The power station comprises two turbines and is operated by Meridian Energy. In October 2012, a high voltage transformer at the power station caught fire, requiring more than fifty fire fighters who worked into the long hours of the night to put the blaze out. The power station was completed in 1957, running two turbines. In 2000, these turbines were each upgraded to.
Etymology
Originally named the Mitta Mitta Dam site, following representations from the Municipal Council of Albury, on 17 February 1920 the River Murray Commission decided to honour Hamilton Hume, who, in company with William Hovell, was one of the first Europeans to see and cross the Murray River in 1824. In 1920, the reservoir was named the Hume Reservoir and the dam adopted the name of the Hume Weir, the name given by the Victorian Place Names Committee. Following a proposal from Hume Shire Council, in 1996 both the NSW and Victorian governments agreed that the dam should be named the Hume Dam, and the reservoir be named Lake Hume.
Lake Hume
Lake Hume is estimated to hold approximately six times the volume of water in Sydney Harbour. The small towns of Tallangatta, Bonegilla and Bellbridge are located on the shores of Lake Hume. The reservoir is often referred to as the Hume Weir, only named Lake Hume in the mid-1980s.
Reservoir levels
Lake Hume is the furthest upstream of the major reservoirs on the Murray River system and has the capacity to release water at the fastest rate. Irrigation authorities used the reservoir as the storage of first resort. The reservoir typically falls to less than one-third capacity by March each year, but in normal years refills to at least two-thirds capacity before November, though Australia's highly unpredictable climatic conditions cause these figures to vary quite significantly from year to year. In 2007 Lake Hume fell to 1% capacity, barely more than the water in the Murray and Mitta Mitta rivers flowing through on their original paths. Between 2010 and April 2013, the lowest storage level was in the range of.
Recreation
The lake is stocked with fish. Most of these are introduced species - carp, redfin and trout though native species such as Golden Perch and Murray Cod can also be found. The fishing varies from year to year. It is also popular for water skiing, and several holiday resorts catering for fishing and skiers are dotted around the upper reaches of the lake. An annual Canoe marathon race the 'Frank Harrison Classic' is run on the river beginning below the dam each February and attracts competitors from across Australia.
Impact on the ecology of the Murray River
The construction of Hume Dam has caused significant changes to the flow patterns and ecology of the Murray River. Before the construction of the Hume Weir, flows in normal years were low in summer and autumn, rising in winter due to seasonal rainfall and reaching a flood-peak in late spring due to snow-melt in the Murray and its tributaries' alpine headwaters. The flow is now effectively reversed, with low flows in winter and sustained, relatively high flows in late spring, summer and early autumn to meet irrigation demands, although the spring flood peak has been virtually eliminated. The water released from the base of the Hume Weir is unnaturally cold, at least 10 °C colder than it naturally should be. This flow reversal, temperature depression, and removal of the spring flood peak, has led to the drying out and loss of many billabongs and has harmed the populations of native fish of the Murray River such as the iconic Murray Cod and the freshwater catfish, which can no longer be found downstream of the dam as far as Yarrawonga, where it had previously been recorded up until the 1960s.
