RESOLVING MURRAY DARLING BASIN WATER ISSUES
At the height of the ‘millenium drought’ Australian TV news cameras highlighted, in somewhat dramatic fashion, sandbanks blocking our continent’s biggest river from reaching the ocean. Viewers were told that too much upstream irrigation was the cause. Interested viewers interstate, and parochial South Australian locals alike, nodded immediate emphatic agreement: If so much water is taken from our big river, that none reaches the sea, we’ve a problem!
Unfortunately, those TV cameras failed to pan back, just a little, to expose the nearby ‘barrages’ which stop ocean tides flowing ‘up the river delta’; or to expose lakeside property development acreage near Goolwa (a popular holiday escape from Adelaide) which was dependent on the barrages, to drown out what otherwise would be tidal mudflats. Nor were TV viewers informed by photos of a bone dry river Murray, above the lakes, taken well before the 1930s.
In the 1930s our Commonwealth, South Australian, New South Wales and Victorian Governments shared equally in the costs of construction of five ‘barrages’ which enabled South Australia to separate the Murray River delta from the Southern Ocean. According to the Murray Darling Basin Authority (Note 1):
“The primary reason for their [the barrages] construction was to keep water fresh in the lower reaches of the River Murray, as well as Lake Albert and Lake Alexandrina. Before the Lower Lake barrages were built, tidal effects and the intrusions of seawater occurred during periods of low flow into the Lower Lakes and in the River Murray, up to 250 km upstream from its mouth.”
Later, the Snowy Mountains Scheme, constructed mainly in the 1950s and 1960s, permanently altered natural environments to the west and southeast of our Snowy Mountains. It did this most profoundly, by forever reducing frequency of flooding, of landscapes around the Snowy, Murray and Murrumbidgee rivers.
Whilst the Snowy River’s flow is substantially reduced, flows today along much of the Murray and Murrumbidgee River channels, now enjoy far greater continuity. Excluding irrigated lands, it is true that their surrounding landscapes (especially floodplains) now receive less water. But it is also true that careful planning can enable key wetlands to receive more regular watering, even if more modest, than occurred prior to damming of those westward flowing rivers.
Similar observations can be made wherever dams have been built elsewhere in the Murray Darling Basin to support irrigation.
The ‘northern (Darling River) basin’ is also impacted by so-called ‘floodplain harvesting’. Given the Darling River valley’s topography, floodplain harvesting arguably harms ‘more environmental acres per litre’ than the damming of any river.
Bottom Line: The major environmental impact of damming rivers for irrigation, is reduction in the extent of flooding of the regions surrounding those rivers (much of which today is agricultural land). The impact is far less, ‘drying out’ of the rivers. Non-indigenous vegetation and introduced carp (which can quickly dominate their environment) are greater threats to most native fish and other riparian wildlife than dams, weirs, irrigation and (good) agricultural practices.
‘Powerpoint Presentation’ (19 slides)
The presentation proposes:
(a) national recognition that environmental water problems in the Lower Murray, are primarily due to infrastructure in South Australia (the ‘Murray barrages’ below Lake Alexandrina and the ‘drainages’ to the Coorong’s southeast);
(b) that South Australia’s infrastructure be rectified and its ocean-side lakes returned to a tidal state;
(c) that the huge amount of environmental fresh water thereby saved (currently used to annually refresh Lakes Alexandrina and Albert) be redeployed upstream, in the wider inland river basin, rather than emptied to the ocean.
This issue should be addressed in advance of the Commonwealth’s review of the Murray Darling Basin Plan which is currently scheduled for 2026.
Rural opposition to the Murray Darling Basin Plan has to a large degree rested on debates, over balancing economic and social interests of rural communities with interests of the environment. A better case, is to call out environmental fraud, through which South Australia’s politicians outwitted eastern state peers.
For a treasuretrove of digestible information on the history and environment of Australia’s Murray River delta and the Coorong, see www.lakesneedwater.org (developed by the late Susan Myers).
Any number of selective environmental reports can be produced to justify the retention of South Australia’s ocean-side Lakes Alexandrina and Albert as fresh-water systems. However no report, taking a holistic approach to the environment (looking for example at total native biomass options) would concur.
This applies most particularly to birdlife which (ironically) provides the crux of the region’s designation as one of Australia’s Ramsar Wetlands. Few if any Australian bird species require freshwater lakes, which stretch beyond the limits of human sight. One does not need to be an ornithologist to appreciate estuary habitats, which involve tide covering and uncovering mudflats and the like, are more appealing for our wading birds and shorebirds, including rarer migratory species visiting the Coorong from Asia. Returning Lake Alexandrina to a tidal status, would greatly multiply the region’s habitats for this birdlife.
Artificial freshwater lakes do the opposite.
For and on behalf of Common Sense for Australia Inc
Authorised for publication, 17 March 2022