Yarrawonga Weir

Dam

Situated on the lands of the Yorta Yorta people,^[5] the earth-filled dam wall is 22 metres (72 ft) high and 489 metres (1,604 ft) long. When full, at 124.895 metres (409.76 ft) above sea level, the resultant reservoir has a storage capacity of 117.5 gigalitres (95,300 acre⋅ft) and covers 4,390 hectares (10,800 acres), drawn from a catchment area of 26,100 square kilometres (10,100 sq mi).^[1]

The controlled ogee crest spillway has a discharge capacity of 3,540 cubic metres per second (125,000 cu ft/s).^[3] The spillway comprises two groups of gates – eight vertical lift gates on a 116-metre-long (381 ft) southern structure and two steel floodgates on a 30-metre-long (98 ft) northern structure. The southern side gates are used at all flow levels. The northern gates are only used during floods larger than 60 gigalitres (49,000 acre⋅ft) per day, to limit environmental damage on the downstream side of the embankment.^[2][6]

During time of high flows and floods, water takes approximately six days to reach the weir from the Murray's headwaters, some 540 kilometres (340 mi) 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 1,992 kilometres (1,238 mi) upriver from the river mouth,^[2] and is the largest of the fourteen weir across the Murray.^[7]

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.^[8] The Mulwala Canal, in New South Wales, has a discharge capacity of 10 gigalitres (8,100 acre⋅ft) per day. The Yarrawonga Main Channel, in Victoria, has a discharge capacity of 3.2 gigalitres (2,600 acre⋅ft) per day. Collectively, the channels release approximately 1,900 gigalitres (1,500,000 acre⋅ft) per annum^[3] to serve an irrigated area of approximately 8,000 square kilometres (3,100 sq mi). Despite having capacity of 117 gigalitres (95,000 acre⋅ft), in order to maintain full supply levels, 113 gigalitres (92,000 acre⋅ft) of the reservoir is inactive.^[2]

The weir serves as a regulator of the flow of the Murray to the Barmah Choke, near Tocumwal.^[2]

Recreational actives on Lake Mulwala include an annual water skiing championship, rowing and sailing regattas, a canoe race from Yarrawonga to Swan Hill, birdwatching, fishing, sailboarding, swimming, boating and guided paddle-boat cruising.^[8]

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.^{[citation needed]} 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.^[8]

Administered by Parks Victoria, Yarrawonga Regional Park is located adjacent to the reservoir, in Victoria.^[9]