Lower Lakes Independent Science Review

Thank you for watching the presentation and for sharing your summary.  

One of the key points to emerge from the review is that the Lower Lakes cannot be managed in isolation.  The Review found that the water that passes through to the Lakes has been used to achieve environmental outcomes upstream and subsequently achieves environmental outcomes in the Coorong and Murray Mouth.  

The evidence is that flows during the drought have been inadequate to achieve the key Mouth Open target and this, along with other threats from Climate Change will need to be addressed through work the SA Government and MDBA are currently planning.  

See more about the Lower Lakes Independent Science Review including the full report with all the detailed information on the findings.

The review examined all the relevant science relating to the management of the Lakes. The work being undertaken by the South Australian Government and the MDBA to identify adaptation strategies for the Coorong will explore opportunities for restoration and their potential social, economic and cultural benefits.  

The Ramsar listing applies to the Coorong, Lower Lakes and Murray Mouth region not just to the Coorong.  More information on Ramsar sites in the Murray–Darling Basin.

Upstream development has reduced the river inflow by about half, resulting in more frequent incursion of seawater into the Lower Lakes, and the barrages were built in 1940 in response to these changes, isolating the Coorong and the sea from the Lower Lakes. Removing the barrages would have a significant ecological and socio-economic impact. The review found that in the past 1 to 2 thousand years the Lower Lakes were largely fresh, with moderate tidal influence of seawater during periods of low river inflows. Without the barrages, the freshwater values in the Lower Lakes could not be maintained and it would significantly change the ecological character of this internationally important wetland, which Australia has an obligation to look after.  

Over time, sea level rises will change the hydrodynamics of the Coorong and Murray Mouth, and increase seawater ingress into the Lower Lakes. There are two main challenges here. First, the barrier islands and the barrages will be overtopped more often. Second, the clogging of the Murray Mouth with sand transported by seawater, which is already happening, will be accelerated. However we need to appreciate that it will be some time before this happens, so we must start planning for this.  This may include engineering solutions. It may include identifying which ecosystems (and the services they provide) can be maintained, those that can transition to some new state, and those that cannot be sustained. It will be important to  know what is needed to help keep the system resilient to enable it to transition to a different future.

The panel did not discuss the south east drainage scheme in detail, except stating that the South East Flow Restoration project would deliver about 6-47 GL/yr to the South Coorong near Salt Creek. The contribution of the scheme to the CLLMM region as a whole is minimal. The South East Drainage scheme puts water into the South Lagoon of the Coorong which is downstream and isolated from the Lower Lakes. There is limited information available on historical flows out of the SE into the Coorong as human activity has been influencing them since the 1860s. 

The projected volumes entering the South Lagoon have relatively minor influence on the Coorong and have been incorporated into the Basin Plan through the sustainable diversion limit adjustment mechanism process. The drainage scheme helps reduce the demand placed on Murray River inflows in achieving salinity targets. The volumes derived from the SE are, however, relatively minor inputs to the system when compared to Murray River inflows. The project was funded collaboratively by the SA and Commonwealth Governments as part of implementation of the Basin Plan as part of efficiently achieving environmental objectives.  More information on the SE flow restoration project.

This question is out of scope for this review.  If you require further information please contact engagement@mdba.gov.au with specific requirements.

The review considered what the impacts of removing the barrages would be because many people had questioned the need for the Lakes to be maintained as freshwater systems. The concept of a lock zero has been previously examined and found not to be feasible and therefore not considered in this review.  

This term was used generally to distinguish "wet" and/or "above average years" from "dry" and/or "below average years". The review did not specifically define what constitutes a "wet year".

We believe that the debate you are referring to is the Peter Gell paper last year that suggests that the seminal study of Fluin et al. in 2007 was misrepresented in a subsequent 2009 Fluin et al. report and in the broader literature, which present the Lower Lakes as predominantly fresh before European settlement. The Panel's assessment is that Fluin et al. in 2009 did not misrepresent the conclusions of the original paper. The original paper in 2007 specifically said “the Holocene diatom assemblages of Lake Alexandrina reflect relatively freshwater conditions with longstanding and major inputs from River Murray, particularly after 2,000 years before present” and “marine water indicators were never dominant in Lake Alexandrina”. 

The review found that in the past 1 to 2 thousand years the Lower Lakes were largely fresh, with moderate tidal influence of seawater during periods of low river inflows. Scientific debates like these are common, particularly with the considerable uncertainty—in the palaeoecological data,  in identifying the diatoms, in relating the different diatoms to salinity, and in dating the sediments particularly when the geomorphology and the hydrodynamics of the system have also been changing over the past 10,000 years.