Sharing the Waters of the Murray-Darling Basin
the Murray-Darling River system begins in Queensland and wends its way
through four states and dozens of Shires and towns, the river itself cares
little for our borders and boundaries. Two reports compiled by the Water for
a Healthy Country Flagship are making the risky business of planning for the
river's future a little clearer.
To a geographer, the Murray-Darling Basin
is a single vast and complex system, with little relationship to the
political boundaries of Australia's states.
Two reports prepared by the Water for a Healthy Country Flagship for the
Murray-Darling Basin Commission (MDBC) take a similarly comprehensive view
of the Basin's water resources. The reports go a long way to describing how
the Basin functions; the interaction of the dams, rivers, groundwater and
wetlands; and the major risks to this vital resource.
Chief Executive of the MDBC, Dr Wendy Craik, says that the member
governments of the Commission are committed to improving the environmental
and economic sustainability of the Basin. The Living Murray project, for
example, is taking practical steps to achieve environmental benefits for six
significant ecological assets along the river; and regulation has been
introduced to limit the volumes of water which may be diverted from the
At the same time, the MDBC identified six major risks which it considered
needed closer investigation: climate change; the increasing numbers of farm
dams; increased groundwater use; the 2003 bushfires; large scale tree
planting; and reduced return flow from irrigation.
Any program to maintain and improve such a complex system will only succeed
if it is based on good data and a sound understanding of the total system.
Dr Mac Kirby and his research team, who prepared the first of the two
reports, emphasise they took a 'whole-of-basin' approach.
"A whole-of-basin approach," they say succinctly, "improves accounting."
"A water balance can help improve the estimates of poorly measured
components. The requirement that all water entering minus all the water
leaving the Basin must equal the change in storage within the Basin can help
constrain the estimates of many components of a water balance."
The first report establishes the hydrological picture at the whole-of-basin
scale, and describes the most important processes which drive the Basin as a
functioning water system: rainfall, evapotranspiration, groundwater, river
flows, dams, diversions and barrages, and the effect of water extraction for
Groundwater has a particularly important role to play, as it is so closely
involved with salinity – the subject of sustained efforts for decades and a
threat into the future.
Lead author of the second report Dr Albert van Dijk says that he and his
research team examined the six risks and attempted to bring them together,
again in a ‘whole-of-basin' approach.
risk shouldn't be confused with a foregone conclusion," says Dr van Dijk.
"Our understanding of how the risks might impact on the Basin is by no means
The report emphasises that most of the six risks do not act in isolation,
but can affect one another. The total impact on river flows cannot be
equated to their sum, but may be more or less severe.
There is one risk however which, the report says, affects all the others
combined as well as individually. And that is climate change.
Is the Basin climate changing? Yes, says the report, there has been a
sustained and statistically unambiguous increase in mean temperatures across
the Basin, matching changes in global temperatures. A study in New South
Wales has also shown that the frequency of extremely high temperatures has
increased since 1957.
This inevitably affects water resources as evaporation rises, rainfall
declines, higher water temperatures affect river ecology, and the effects of
drought are exacerbated.
Dr van Dijk says that an important element of the two reports has been to
identify areas where research is needed.
"We looked specifically at the key knowledge gaps that affect our ability to
assess the impact of each of the six risks on future water resources"
The two linked reports are an
important tool for the sustainable management of the shared water resources
of the Murray-Darling Basin.
Water Resources of the Murray-Darling Basin (part 1)"
"Risks to the Shared
Water Resources of the Murray-Darling Basin (part 2)"
Dr Mac Kirby: 02 6246 5921 Mac.Kirby@csiro.au
Dr Albert van Dijk: 02 6246 5780 Albert.VanDijk@csiro.au
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The Ring of Confidence - Incorporating Uncertainty into
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