Travelling Australia Fact Sheet  http://www.travelling-australia.info	HOME   LIST   BACK

Yarrawonga Weir and Lake Mulwala - Vic & NSW

Yarrawonga Weir maintains water levels in the Murray River so that water flows without pumping into two major irrigation supply channels flowing into New South Wales and Victoria. Lesser roles for the weir are to regulate flow downstream to Barmah-Millewa forest and Echuca and to play a role in flood-mitigation but the volume of Yarrawonga Weir is small compared with other storages in the Murray system and it can have little effect on flooding water flows. Yarrawonga Weir is located near the townships of Yarrawonga in Victoria, and Mulwala in New South Wales. Construction of the weir began in 1935 and was completed in 1939. The first diversion of water into the two canals fed from the weir took place in October 1939. There is no lock associated with the weir to allow boats to pass the weir since the River Murray Waters Agreement of 1915 provided for navigation upstream only as far as Echuca. A privately owned hydro-electric station and a fish lift were added to Yarrawonga Weir in 1994. Lake Mulwala, formed by the weir, is a popular recreational water sports centre. Description Yarrawonga Weir is the largest of 16 weirs controlled by the Murray-Darling Basin Commission. It comprises two groups of gates; one group of eight gates on a southern structure used for all flows and the second group of two gates on the northern side only used during heavy floods to stop flows along the downstream side of the embankment that could cause erosion. The gates can be raised above the water flow if required. By local request, based on the fact that more than a million sheep had crossed the Murray River at Yarrawonga between 1931 and 1935, a 6.1 metre wide stockroute was built beside the road across the downstream side of the weir. The hydro-electric power station at Yarrawonga Weir has a nominal capacity of 9.0 MW. Construction of the power station was completed in 1995 by a private company. It uses water released from Lake Mulwala to generate electricity sold to the Victorian grid. The power station is unusual in that it operates on a very low head of water, down to 3 metres. The catchment for Yarrawonga Weir is the Murray River below Hume Dam, the Kiewa and Ovens Rivers. When Yarrawonga Weir was built and Lake Mulwala formed, a long-existing red-gum forest was flooded. Many of the trees were cut down by volunteer local labour before the lake filled but many dead trunks remain dotted around the lake. Operation Yarrawonga Weir is the point of greatest diversion of water from the Murray River. Mulwala Canal on the New South Wales side has a discharge capacity of up to 10,000 megalitres a day while Yarrawonga Main Channel on the Victorian side has a discharge capacity of 3,200 megalitres a day. These two canals supply water to a total area of more than 8,000 square kilometres. Mulwala Canal into New South Wales passes near Deniliquin, then divides into feeder channels serving the Southern Riverina Irrigation District roughly bounded by a line from Yarrawonga to Jerilderie, Moulamein, Barham and Tocumwal. West of Deniliquin this area produces a large amount of rice; east of Deniliquin is primarily a beef cattle region using irrigated winter pasture and producing fat lambs, wool, wheat and barley. Sorghum, maize and oilseed are developing as summer crops throughout the Southern Riverina. In Victoria, the Yarrawonga Main Channel runs to the west of Yarrawonga soon dividing to serve the Murray Valler Irrigation Area in Victoria between Yarrawonga and Barmah. Most irrigated properties are devoted to dairy pasture. Around Shepparton and Cobram peaches, pears and apricots are grown; beef cattle, fat lambs and sheep for wool are also present. Lake Mulwala, formed by Yarrawonga Weir, has a full capacity of 118 gigalitres; much smaller than Lake Hume (3,038 gigalitres). Relying on gravity feeds into the supply canals means that only the top few metres of water in the lake can flow into the canals and the active storage is only 5 gigalitres. If necessary, the lake can be surcharged by 0.25 metres for brief periods providing a further 11 gigalitres of active storage.

When Yarrawonga Weir was complete and Lake Mulwala began to fill a red gum forest was submerged killing the trees which remain in the lake.

Information: ¶  Murray Darling Basin Commission at http://www.mdbc.gov.au.htm ¶  Harnessed Waters - A River Dammed, edited by A. Noel Loughnan. Pub Yarrawonga Shire Council, 2004 edition.

TOP