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Millennium Drought

From late 2001 to 2010 the River Murray region experienced a significant drought known as the Millennium Drought.

River Murray flows reached historically low levels due to the combined impacts of extreme drought and decades of over-allocation across the Murray–Darling Basin. A combination of low rainfall and the lowest inflows into the river in recorded history meant flows over the border into South Australia virtually ceased.

Adelaide’s water supply was threatened, and pipelines had to be built to deliver drinking water to the Lower Lakes communities and sustain horticultural industries.

Supplies to the nearly 4000 South Australian irrigators that get their water from the River Murray were severely restricted, putting pressure on agricultural and horticultural industries and regional communities.

33 wetlands were temporarily disconnected to help save water, risking long-term damage to those environments. For example, many were colonised by introduced terrestrial species.

Connectivity (both hydrological and ecological) was lost between Lake Alexandrina, the Goolwa Channel and Lake Albert. The Lower Lakes began to dry up, exposing acidic soils, and the Murray Mouth closed, forcing around-the-clock dredging to ensure salt and other pollutants could be flushed out of the river system.

Diadromous fish species, the lifecycles of which require movement between freshwater, estuarine and marine habitats, were unable to pass through the barrages to complete their life cycle due to the low water levels in Lake Alexandrina.

Parts of the Coorong became too salty for many native plants and animals to survive, becoming five times saltier than the sea.

At the peak of the drought:

flows across the South Australian border fell to just 960 GL per year
Adelaide was placed on Level 3 water restrictions
irrigators started 2008-09 and 2009-2010 with the lowest starting allocation on record – just 2 per cent
low water levels caused riverbank collapse along the river below Lock 1
lakes Alexandrina and Albert reached their lowest point in a thousand years with the water level in Lake Alexandrina plunging to 1.1 metres below sea level in April 2009
20,000 hectares of acid sulfate soils were exposed in the Lower Lakes region
salinity reached record levels, damaging ecosystems and threatening water supplies for people and livestock
the Murray Mouth almost closed in 2002, triggering the start of round-the-clock dredging for the following eight years
Aboriginal communities suffered the exposure of ancient burial grounds.

Dr Luke Mosley of the Environmental Protection Agency discusses water quality risks in the lower River Murray and lakes associated with the extreme drought.

Assessing and managing water quality risks in the Lower River Murray and Lakes

Drought recovery

There are many signs of improvement, but a sustained effort is needed to ensure we have a healthy, working river now and in the future.

Much work has been done to help drought recovery and build resilience into the river system so it is better able to cope with future droughts.

Basin-wide

The Millennium Drought highlighted that too much water had been taken from the Murray-Darling Basin for too long. There was not enough water available to keep the ecosystem healthy and resilient to droughts.

As a result, the independent Murray-Darling Basin Authority was formed and made responsible for developing a plan to ensure the entire Murray-Darling river system is managed sustainably into the future.

The Basin Plan ensures that the environmental needs of the basin’s rivers, wetlands and floodplains are protected, while sustaining food production and communities. South Australia now works with other basin states, the Australian Government and the Murray-Darling Basin Authority to implement the plan.

Long-term plan

A long-term plan to secure a healthy, sustainable future for the internationally significant Coorong, Lower Lakes and Murray Mouth wetlands was developed to complement the Basin Plan. It aims to build resilience into the environment so that it can recover and is better able to cope in future dry times.

Traditional Owners, communities and industries across the region provided input into the plan to ensure the latest science and local knowledge was incorporated. They also play an important role in delivering the plan.

This video highlights the valuable planting work carried out by community groups and volunteers to tackle acid sulfate soils and help the environment recover from drought.

A range of projects have also helped:

the river’s wetlands and floodplains, Lower Lakes, Coorong and Murray Mouth to recover from drought and build resilience into the river system
support the irrigation industry to improve their water efficiency and diversify their businesses into more water efficient areas.

Find out more about drought, drought assistance and farm support:

Community planting in the Coorong Lower Lakes and Murray Mouth region

See videos of drought recovery under the CLLMM Recovery Project.

Frequently asked questions about the Millenium Drought

What measures did South Australia undertake to protect the environment?

Purchased water to help maintain water levels in the lakes.
Permanent wetlands were temporarily closed to prevent high salinity and nutrient rich water from draining back into the river.
Undertook additional monitoring for salinity, acid sulfate soils and riverine ecology.
A range of projects around the Lower Lakes resulted in:
o temporary barriers being built at Narrung, Goolwa and Currency Creek to manage the acid sulfate soil risk and provide an ecological refuge
o rescued a population of Murray-Hardy Head and kept them on land until the conditions improved.
o 2029 tonnes of limestone applied by air
o 1978 tonnes of limestone applied as barriers
o approximately 6,580 ha of land revegetated either by machine seeding (air or land) and hand planting
o 130,000 seedlings being planted on higher ground around lakes.
Contracted the University of Western Australia to undertake acidification prediction studies, using bio-geochemical modelling to determine acidification triggers in the Lower Lakes.
Commenced the Coorong, Lower Lakes and Murray Mouth Program and the Riverine Recovery Program.

What measures did South Australia undertake to support critical human water needs?

Implemented water conservation through restrictions, rebates on low flow devices and rainwater tanks.
Implemented contingency options by the temporary closure of wetlands to save evaporative losses.
Developed a State Water Security Plan that diversified Adelaide’s water supplies through construction of the Adelaide Desalination Plant, waste water recycling and stormwater harvesting schemes.
Modified the major River Murray pumping offtakes for Adelaide’s water supply, constructed new pipelines around the Lower Lakes and fast tracked the country water quality improvement program.
Pumped water into storages in the Adelaide Hills, where the evaporation is less to provide a buffer against potential water quality issues.
Secured a water reserve each year to provide for critical human water needs and built additional water reserves through market purchase.
Provided assistance to the Riverland horticultural industry by purchasing water to keep permanent plantings alive.
Extended footings on ferries to allow them to operate at lower river heights and fast tracked environmental approvals for dredging of the Murray Mouth to enable navigation and to provide water for the Coorong.
Undertook investigations into levee bank cracking and failure.
Undertook an Environmental Impact Statement for a temporary weir near Pomanda Island (Wellington Weir).

Why don't we open the barrages during dry times?

Acidification in the Lower Lakes was a significant risk during the Millennium Drought, but letting in seawater would have had an even more serious impact and would irreversibly damage this Ramsar site.

Opening the barrages and introducing seawater was considered and investigations were conducted to fulfill statutory requirements. It was found that the introduction of seawater would likely lead to extreme increases in salinity and heavy metals, creating a hypersaline toxic ecosystems. A healthy, estuarine/marine community would not establish.

From the knowledge gained through the Millennium Drought, the “Drought Emergency Framework for Lakes Alexandrina and Albert” was developed and agreed by Ministerial Council. The Emergency Framework provides decision-making steps and potential management actions. The consideration of selected options needs to be made against a range of environmental, social and economic factors that would be applicable at that time.

Why doesn’t South Australia construct a permanent weir at Wellington?

A weir at Pomanda Island was investigated during the Millennium Drought as an option for maintaining water levels between Wellington and Lock 1. The proposal was for a temporary structure and was designed for a nominal three year life. An EIS assessment process was undertaken in the event that it was needed, but the weir was not pursued as water levels were reinstated before the criteria for its construction were met.

It is not possible to construct a permanent weir. The sediments are so soft and bedrock so deep that even a temporary weir at the site would continuously sink and would require regular reinstatement at significant cost.

With a weir in place, a minimum through flow would be required to avoid major water quality issues upstream of the weir. It was found that the volume required would actually be sufficient to maintain suitable water levels in the Lower Lakes, removing any necessity for a weir (or for the introduction of seawater).

Can SA Water’s offtakes be moved above Lock 1?

Apart from being a lengthy and costly process, it would be expected to require additional water from New South Wales and Victoria to ensure there was sufficient water in the weirpool above Lock 1 at peak times so the required quantities could be extracted from multiple extraction points at once.

There are also stock and domestic, irrigation and industrial water users below Lock 1 that would be required to be supplied.