Yarrawonga Weir

The Yarrawonga Weir is an earth-filled embankment dam across the Murray and Ovens rivers, located between and in the Hume region of Victoria and in the Riverina region of New South Walesin eastern Australia. The weir, situated in Victoria, was completed in 1939 to form the reservoir, Lake Mulwala, for the purposes of water supply for irrigation in the surrounding district, regulate river flow, and serve as a crossing of the Murray between Victoria and New South Wales. A hydroelectric power station and a fish lift were added in 1994.

Owned by the Murray–Darling Basin Authority, the dam and reservoir are operated by Goulburn–Murray Water. Transport for New South Wales manages the waterway and the NSW Department of Primary Industries manages fishing on the reservoir.

Dam and reservoir overview Dam Situated on the lands of the Yorta Yorta people, the earth-filled dam wall is high and long. When full, at above sea level, the resultant reservoir has a storage capacity of and covers , drawn from a catchment area of .

The controlled ogee crest spillway has a discharge capacity of . The spillway comprises two groups of gateseight vertical lift gates on a southern structure and two steel floodgates on a northern structure. The southern side gates are used at all flow levels. The northern gates are only used during floods larger than per day, to limit environmental damage on the downstream side of the embankment.

During time of high flows and floods, water takes approximately six days to reach the weir from the Murray's headwaters, some to the east. The Yarrawonga Weir is the farthest downstream dam or weir across the Murray that does not have a navigation lock through it. The weir is upriver from the river mouth, and is the largest of the fourteen weir across the Murray.

Reservoir Below the weir, two gravity-fed channels supply water for irrigation. Developed as part of the Murray-Darling Irrigation Scheme, this irrigation project enhanced the productivity and prosperity of the district and provided opportunities for war veterans as part of a World War II–soldier settlement scheme. The Mulwala Canal, in New South Wales, has a discharge capacity of per day. The Yarrawonga Main Channel, in Victoria, has a discharge capacity of per day. Collectively, the channels release approximately per annum to serve an irrigated area of approximately . Despite having capacity of , in order to maintain full supply levels, of the reservoir is inactive.

The weir serves as a regulator of the flow of the Murray to the Barmah Choke, near Tocumwal.

Recreational actives on Lake Mulwala include an annual water skiing championship, rowing and sailing regattas, a canoe race from Yarrawonga to , birdwatching, fishing, sailboarding, swimming, boating and guided paddle-boat cruising.

The reservoir is a renowned for the native Murray cod and is one of the few places where this Australian native freshwater fish is still reasonably common. The reservoir is a breeding ground for pelicans and it has several ibis rookeries. At 45 holes, the town of Yarrawonga has the largest golf course in Australia. Flooding of the area resulted in many Murray River Red Gums dying and their submerged trunks poke out of the reservoir.

Administered by Parks Victoria, Yarrawonga Regional Park is located adjacent to the reservoir, in Victoria.

Hydroelectric power station The Yarrawonga Weir Power Station is a run-of-the-river hydroelectric power station that was commissioned in 1994. With a generating capacity of , the station has two Kaplan turbines, each with a capacity to generate . Operated by AGL Energy, the station is connected to the Victorian electricity grid via a 22 kV transmission line, and has an average annual output of .

Bridges The Mulwala Bridge, a road bridge across Lake Mulwala, was built between 1917 and 1924, before the weir was completed and the reservoir filled. The road replaced an earlier wooden bridge built between 1889 and 1891. The 1924 road bridge bridge was started from both ends, each by the respective state government. However, they did not coordinate their efforts, and the bridge has a dip and a bend in the middle to make the two ends meet.

Additionally, a small bridge along the weir served as a crossing of the Murray that was in operation from 1939 until its closure to motor vehicles in 2021, in order to protect the structural integrity of the weir.

The reservoir is also crossed by a railway bridge.

Gallery

Yarrawonga Weir

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