Lower Lakes, Coorong and Murray Mouth

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murray-darling basin logo2013 report cover2

Lower Lakes, Coorong
and Murray Mouth

Environmental Water Management Plan

aerial photo of an open murray mouth

May 2014

Lower Lakes, Coorong and Murray Mouth

Environmental Water Management Plan

Published by Murray–Darling Basin Authority.

MDBA Publication No 10/14

ISBN 978-1-922177-81-0 (print) ISBN 978-1-922177-82-7 (online)

© Murray–Darling Basin Authority for and on behalf of the Commonwealth of Australia, 2013.

With the exception of the Commonwealth Coat of Arms, the MDBA logo, all photographs, graphics and trade marks, this publication is provided under a Creative Commons Attribution 3.0 Australia Licence.

cc by logo - creative commons licencing info

The MDBA’s preference is that you attribute this publication (and any material sourced from it) using the following wording:

Title: Lower Lakes, Coorong and Murray Mouth Environmental Water Management Plan

Source: Licensed from the Murray–Darling Basin Authority, under a Creative Commons

Attribution 3.0 Australia Licence.

The MDBA provides this information in good faith but to the extent permitted by law, the MDBA and the Commonwealth exclude all liability for adverse consequences arising directly or indirectly from using any information or material contained within this publication.

Cover image: River Murray Mouth

Photographer: Taken and supplied by SA Water staff member (unspecified person).

Acknowledgement of the Traditional Owners of the Murray–Darling Basin

The Murray–Darling Basin Authority (MDBA) acknowledges and pays its respect to the Traditional Owners and their Nations of the Murray–Darling Basin. The contributions of earlier generations, including the Elders, who have fought for their rights in natural resource management are also valued and respected.

MDBA recognises and acknowledges that the Traditional Owners and their Nations in the Murray–Darling Basin have a deep cultural, social, environmental, spiritual and economic connection to their lands and waters. MDBA understands the need for recognition of Traditional Owner knowledge and cultural values in natural resource management associated with the Basin. Further research is required to assist in understanding and providing for cultural flows. MDBA supports the belief of the Northern Murray–Darling Basin Aboriginal Nations and the Murray Lower Darling Rivers Indigenous Nations that cultural flows will provide beneficial outcomes for Traditional Owners.

The approach of Traditional Owners to caring for the natural landscape, including water, can be expressed in the words of Ngarrindjeri elder Tom Trevorrow: ‘our traditional management plan was don’t be greedy, don’t take any more than you need and respect everything around you. That’s the management plan—it’s such a simple management plan, but so hard for people to carry out.1 This traditional philosophy is widely held by Traditional Owners and respected and supported by MDBA.


The Living Murray initiative is one of Australia’s most significant river restoration programs, with the long-term objective to achieve a healthy, working River Murray system. Six icon sites along the River Murray have been identified that have significant ecological, cultural, recreational, heritage and economic values. Ecological objectives (First Step Decisions), were derived from the Outcome Evaluation Framework and have been determined for each icon site to guide the improvement in icon site environmental health.

Lakes Alexandrina and Albert (the ‘Lower Lakes’), the Coorong and Murray Mouth (LLCMM) have been identified as an icon site. The LLCMM icon site covers approximately 140,000 ha, is a Ramsar-listed wetland of international importance and is also one of eighteen key indicator sites of the Murray–Darling Basin. The site has a unique mosaic of 23 Ramsar wetland types and provides habitat for nationally significant species. The icon site, which contains the Meeting of the Waters registered heritage site, is central to the life and culture of the Ngarrindjeri people, who continue to live on their traditional country.

The ecological health of the icon site has been severely degraded by river regulation, over-extraction, and to a lesser extent a reduction in the diversion of drainage water from the South East into the Coorong South Lagoon. These impacts have been exacerbated in recent times by a prolonged period of drought. Through The Living Murray initiative First Step Decision, the Murray–Darling Basin Ministerial Council (MDBMC) established three broad ecological objectives to improve the condition of the LLCMM icon site:

  • an open Murray Mouth

  • more frequent estuarine fish spawning and recruitment

  • enhanced migratory waterbird habitat in the Lower Lakes and Coorong.

In order to achieve these objectives, 16 LLCMM-specific ecological and physical targets have been developed to quantify changes in the condition of the site.

The purpose of this Environmental Water Management Plan (EWMP) is to define the environmental water needs for the LLCMM, based on the volumes and flow regimes required to achieve the ecological objectives and targets of the icon site. Delivery of flows to the Lower Lakes through the River Murray system to maintain water level, water quality and to prevent exposure of acid sulphate soils, has been identified as the key requirement to achieve the icon site ecological objectives and targets. Sufficient inflows to the Lower Lakes will also allow barrage releases to ensure connectivity between all parts of the icon site (Lake Alexandrina/estuary, and estuary/ocean), maintain an open Murray Mouth, estuarine habitats and water level and quality throughout the Coorong ecosystem. Water quality thresholds have been determined for Lake Alexandrina (electrical conductivity below 1,000 μS/cm 95% of the time, and below 1,500 EC 100% of the time) and the Coorong (salinity below 100 ppt in the South Lagoon) in response to the physiological tolerance of the icon site’s fauna and flora.

The proposed environmental water requirements to achieve the LLCMM icon site First Step Decisions, in order of priority, are:

  1. Water is provided to maintain lake levels above 0.0 m Australian Height Datum (AHD) to prevent exposure of acid sulfate soils and to maintain connectivity between Lakes Alexandrina and Albert.

  2. Water is provided to maintain lake levels within the seasonal operating envelope (0.350.75 m AHD, and every three years 0.5-0.83 m AHD).

  3. Fishways are operated year-round (55 GL/yr).

  4. Attractant flows are provided adjacent to fishways, and a limited estuary achieved in Boundary Creek (up to 230 GL/yr, with spring-summer priority timing).

  5. Minimum annual flow from the barrages required to achieve salinity target of <1,000 μS/cm in Lake Alexandrina 95% of the time (650 GL/yr minimum in any year incorporating a three-year average of 2,000 GL/yr).

  6. Minimum annual flow required to keep the Murray Mouth open (730—1,090 GL/yr).

  7. Flows of at least 2,500 GL over two years to prevent the Coorong existing in a degraded ecosystem state.

  8. Flows of 6,000 and 10,000 GL per year every three and seven years respectively to achieve a healthy Coorong ecosystem state.

These environmental water requirements were developed to provide information on how much water the site requires to function in a ‘healthy’ ecosystem state, regardless of what is available in environmental water portfolios. It is not expected that The Living Murray portfolio will be able to meet the full water requirements for the LLCMM icon site.

Requirements 1-3 are likely to be met by South Australian Entitlement Flow (1,850 GL/year). Achieving requirements 3-8 will require periods of above entitlement flow supplemented by significant volumes of environmental water from both The Living Murray and from the Commonwealth Environmental Water Holder. Requirement 8 will also require significant volumes of unregulated flow. The ecological and physical outcomes supported by actions proposed in this EWMP will be assessed by monitoring programs and ecological modelling with ongoing significant input from the scientific community. The LLCMM Icon Site EWMP has been developed, and will be implemented, in consultation with the community and the Ngarrindjeri Regional Authority (NRA). Close collaboration with the NRA will continue regarding their aspirations for the management, protection and enhancement of the Lower Lakes, Coorong and Murray Mouth as a site of enormous cultural significance.

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