River Murray Barrages Environmental Flows

17 October 2010

In October 2010, the Murray Darling Basin Authority (MDBA) released its Guide to the Proposed Murray Darling Basin Plan.  You can read more about this guide here.

What a difference 10 years makes

Over ten years ago, in June 2000, the Murray Darling Basin Commission (MDBC), the precursor to the MDBA, produced this insightful report (cached).

The earlier 2000 MDBC report evaluated the environmental flow needs in the Coorong, Lower Lakes and Murray Mouth (CLLMM) focusing primarily on the following two issues:

• • the altered input flows in the Lower Lakes and Coorong due to upstream river regulation

  • the altered lake and estuary flows due to the construction of barrages separating the lakes from the mouth and the Coorong

Four key issues driving the serious degradation of environmental values in the Lower Lakes and Coorong were identified, namely:

• • the reduced area of the estuary

  • changed water regimes of the lakes and river

  • freshening of brackish and saline habitats

  • reduced habitat for aquatic plants

The first two issues were identified as the most significant in terms of their impact, and specifically the reduction of the tidal prism of the River Murray estuary, i.e., the area of the Lower Lakes affected by tides, to around 90% of its original pre-barrage size. Note that this was considered problematic in 2000, well before the onset of the most recent drought of 2003-2009,

The report concludes that "the current operating system for the Lower Lakes, Coorong and Murray Mouth is not sustainable with continued significant environmental degradation expected."  One of the long-term (> 10 year) recommendations (p. 155) in the report was "the removal of the barrages to Wellington".

The June 2000 MDBC report was remarkably prescient.  It is a great shame that its findings have been largely ignored by the latest MDBA report.