Wellington Weir is a proposed weir

Weir

A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

 on the River Murray at or near the town of Wellington, South Australia

Wellington, South Australia

Wellington is the small town in South Australia on the Murray River just upstream of where it empties into Lake Alexandrina. Its postcode is 5259. Wellington is in the Rural City of Murray Bridge...

, not far upstream from where the river flows into Lake Alexandrina

Lake Alexandrina (South Australia)

Lake Alexandrina is a lake in South Australia adjacent to the coast of the Southern Ocean, about 100 kilometres south-east of Adelaide.-Name:The lake was named after Princess Alexandrina, niece and successor of King William IV of Great Britain and Ireland...

.

Announced in 2006 by the state government of South Australia

South Australia

South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...

, the proposed Wellington Weir is suggested as an attempt to secure drinking water supplies for the city of Adelaide

Adelaide

Adelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...

. The weir would perform two roles, first it would maintain a pool of water up-river, sufficiently deep enough to allow continued use of the pumping station at Mannum

Mannum, South Australia

Mannum is an historic town on the west bank of the Murray River in South Australia, east of Adelaide. At the 2006 census, Mannum had a population of 2,042. Mannum headquarters the Mid Murray Council, and is situated in both the State Electoral District of Schubert and the federal Division of...

 during prolonged drought conditions. Second, the weir would reduce the flow of fresh water into Lake Alexandrina

Lake Alexandrina (South Australia)

Lake Alexandrina is a lake in South Australia adjacent to the coast of the Southern Ocean, about 100 kilometres south-east of Adelaide.-Name:The lake was named after Princess Alexandrina, niece and successor of King William IV of Great Britain and Ireland...

 and Lake Albert

Lake Albert (South Australia)

Lake Albert is a notionally fresh water lake near the mouth of the Murray River. It is filled by water flowing in from Lake Alexandrina at its mouth near Narrung. It is separated on the south by the Narrung Peninsula from the salt-water Coorong. The only major town on the lake is Meningie...

 which lose over 1,000 gigalitres of water a year to evaporation

Evaporation

Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

.

Much of the river is already controlled by a system of locks and weirs, including the barrages near the mouth, and Lock 1 upstream at Blanchetown

Blanchetown, South Australia

Blanchetown is a small township in South Australia, on the bank of the Murray River, 130 km northeast of Adelaide.  The Blanchetown Bridge is the western-most of the four crossings of the Sturt Highway over the Murray River.  During the nineteenth century it was an important...

, 274 km from the Murray Mouth. The lowering of water levels in the lake system would severely impact on all who rely on the Lakes and River for their livelihood. This would include irrigators, such as the Langhorne Creek

Langhorne Creek, South Australia

Langhorne Creek is a town and wine region in South Australia. It is less than an hour's drive from Adelaide on Fleurieu Peninsula. At the 2006 census, Langhorne Creek had a population of 1,198.-Wine Industry:...

 wine region, farmers on the Narrung Peninsula and Point Sturt and fisher people at Meningie and Clayton, to name a few.

Opponents of the weir contend that the planned weir could kill the Coorong, and that already endangered species in the Lakes and Coorong could become extinct. Sim and Muller (2004) trace the complex history of the area. Lloyd (2007) argues the weir diverts attention from the real issue: the sustainability of the Murray-darling system. There has been no Environmental Impact Assessment regarding the proposed weir. The area impacted is subject to a Ramsar Agreement (Australian Government 2006), as part of an international convention that aims to halt the loss of wetlands and conserve those that remain through wise use and management.

Questions of over-allocation loom large in the debate regarding the cost of a weir (Australian Conservation Commission). For instance, why not spend money on buying water licenses from irrigators that use water from the Murray River system to grow cotton in Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

instead of a weir? (The Australian 2007).

Local Actions Groups formed to oppose the weir point out that the water held back by the proposed weir would be stagnant because "winds from the northwest to the south circulate oxygenated waters from the lakes up the river for many kilometres and winds from the north and northeast bring back freshened water benefiting both areas and precisely fitting in with our anti-clockwise wind rotation" (Jones 2007; see also Webster et al. 1997).