Мура-Дарлинг бассейні: Австралияның ең ірі су жемі

Largest Australian river catchment

The Murray–Darling Basin is a large geographical area in the interior of southeastern Australia, encompassing the drainage basin of the tributaries of the Murray River, Australia's longest river, and the Darling River, a right tributary of the Murray and Australia's third longest river. The Basin, which includes six of Australia's seven longest rivers and covers around one seventh of the Australian landmass, Located west of the Great Dividing Range, it drains southwest into the Great Australian Bight and spans most of the states of New South Wales and Victoria, the Australian Capital Territory, and parts of the states of Queensland (the lower third) and South Australia (the southeastern corner). The Basin is in length, with the Murray River being long. Most of the basin is flat, low lying and far inland, and receives little direct rainfall. The many rivers it contains tend to be long and slow flowing, and carry a volume of water that is large only by Australian standards. The Snowy Mountains Scheme provides some security of water flows to the Murray–Darling Basin, providing approximately 2,100 gigalitres (7.4×1010 cu ft) of water a year to the Basin for use in Australia's irrigated agriculture industry, which is worth about A$3 billion per annum, representing more than 40% of the gross value of the nation's agricultural production.

The Basin was once home to a large number of Aboriginal people whose traditional lifestyle and cultures were gradually altered by the arrival of Europeans, while others were outright killed by the settlers. Although some tribes organised resistance, such as the Maraura, whose territory lay around the Rufus River above Renmark and the Tanganekald near The Coorong, they were eventually either killed, exiled, or succumbed to disease.

Four varieties of carp were used to stock up fish dams. Since then they have made their way into the river systems, where they spread quite quickly. Human introduction, possibly by anglers using small carp illegally as live bait, has also increased their distribution. These fish are very mobile, breed rapidly and can survive in very shallow water and through long periods of very low dissolved oxygen content. Carp are a problem because they feed by sucking gravel from the riverbed and taking all the edible material off it, before returning the rest to the water. This stirs up all the sediment, reducing the quality of the water. A project for developing daughterless carp shows promise for eliminating carp from the river system. Cane toads have entered the upper reaches of the Darling Basin and there are several reports of individuals being found further down the system. Cane toads compete with native amphibians and are toxic to native carnivores. Phyla canescens has invaded wetlands and floodplains with heavy clay soils in the Murray–Darling Basin, to the detriment of the native vegetation; the plant does best in habitats that are inundated occasionally, although it cannot compete with the grass Paspalum distichum and the sedge Eleocharis plana in more heavily inundated sites.

The Basin affects five states and territory governments, which according to the Constitution, are responsible for managing water resources. The River Murray Commission was established in 1917. This led to minor reforms in 1982 in which water quality became part of the commission's responsibilities. The Plan was in response to the 2000s Australian drought, and designed to secure the long term ecological health of the Murray–Darling Basin. This entailed cutting existing water allocations and tree growth environmental flows. The Basin Plan was designed to set environmentally sustainable limits on the quantities of water that may be taken from Basin water resources, to set Basin wide environmental, water quality and salinity objectives, to develop efficient water trading regimes across the Basin, to set requirements for state water resource plans and to improve water security for all Basin users. It also intends to minimise social and economic impacts whilst achieving the plan's environmental outcomes. With the release of the Guide to the Proposed Murray–Darling Basin Plan there have been a number of protests and voiced concerns about the plan in rural towns that the MDBA visited to present the plan to consultation meetings. More than 5,000 people attended a MDBA meeting in Griffith where Griffith Mayor, Mike Neville, said the plan would "obliterate" Murrumbidgee valley communities. Other groups also echo this feeling, such as the Victorian Farmers Federation and Wine Group Growers' Australia. Conversely, support for the Murray–Darling Basin plan has been received by various groups, including Australian Conservation Foundation, and Environment Victoria. New legal advice from Commonwealth government lawyers is changing the plan. The Government's interpretation is that the plan must give equal weight to the environmental, social, and economic impacts of proposed cuts to irrigation. Environmentalists and South Australian irrigators, at the end of the river in South Australia, say that the authority should stick to its original figure. In October 2010, a parliamentary inquiry into the economic impacts of the plan was announced. In late October 2010 the Water Minister, Tony Burke, played down the prospect of a High Court challenge to the Murray–Darling Basin plan, as confusion continued over new legal advice released by the Government. In response to community concerns that MDBA had put environmental issues first over social and economic needs, Burke released new advice on the requirements of the Water Act. Burke stated that the Act does allow for the authority to "optimise" the needs of all three areas, but constitutional lawyer, George Williams, had cast doubts over the interpretation of the laws, stating it could be subject to a legal challenge. The MDBA announced in November 2010 that it might be forced to push back the release of its final plan for the river system until early 2012. The then MDBA chairman, Mike Taylor, reassured the public meeting that more work is being done to look at how the proposed cuts would affect regional communities. He stated: "Importantly, we want to make sure the social and economic impacts—which under any sort of scenario is very significant—were fully teased out". Taylor resigned as he allegedly believed that the overriding principle should be the environmental outcome which was in conflict with the Gillard Government and following a period of sustained criticism of the Authority and the implementation of the proposed draft Basin plan. He was replaced by former New South Wales Planning Minister, Craig Knowles. In late May 2012, the revised plan was forwarded to state water ministers. It did not alter the recommendation to cut of water entitlements. Following much negotiation between the Commonwealth and State governments and numerous submissions from interested stakeholders and the community, the Basin Plan became law in November 2012 and can now be implemented.