How should we deal with the Murray River?
Reproduced below is the full text of the latest Droplet, an irregular email sent out addressing concerns within the Murray River. I encourage people to check out Mike Young's water website. As well as being able to subscribe to Droplet, it is a veritable treasure trove of other useful water and Murray Darling Basin related publications.
(The formatting is copied from the original email)
"More from less: When should river systems be made smaller and managed differently?
“Less is more.” Ludwig Mies van der Rohe
In this Droplet, we discuss the case for reconfiguring rivers and the water-dependent ecosystems associated with them. We envisage a world where the approach to environmental, water quality, stream flow and stream height management is quite different to the way it is today.
Recent announcements that inflows into the River Murray over the last three years were less than half the previous three year minimum that occurred between 1943 and 1946, suggest that it may be time to reconsider the river and the environment we have created through the installation of barrages, locks, weirs and dams. In recent years and as currently configured, evaporative losses have been similar to inflows. Very little water has been available. Irrigators, urban water users and the environment have been doing it tough!
The apparent shift to a drier climatic regime than previously experienced may be here for some time – perhaps for the long term. One way planning for and of coping with such an adverse climate shift is to reconfigure the river – make it smaller, manage it differently and get more flow.
We stress that this is not a new idea. In the last two years, South Australia has closed off over thirty wetlands and moved many irrigation off-take points from backwaters into the main river channel.
Similarly, Murrumbidgee Irrigation has constructed a set of banks across Barren Box Swamp that split it into a number of cells so that water can be stored in parts rather than all of the swamp. This has reduced evaporative losses and has enabled a more diverse environment to be created. A win-win outcome.
Another example is Victoria’s decision to decommission the inefficient and man-made Lake Mokoan water storage and rehabilitate the wetland that once lay under this lake. In the Wakool system in NSW, the idea of threading water through part of the system is under serious consideration. A dynamic management regime has been in place there since 1996.
In a drier regime, is there a smarter way to configure and run a river? Can we get more water to use and better outcomes for the environment from less river?
What would happen if all river infrastructure and all wetlands, waterways and floodways throughout the system were examined carefully with a view to reducing evaporation and using the savings to improve environmental outcomes? Why not water some areas well and leave the fate of the rest to chance.
Pushing the boundary further, in a drier regime, would it make sense to change the way a river is operated? How much should be kept navigable? Should river salinity be allowed to rise in winter on the understanding that it will be lowered in summer?
Why, when so much is being invested in irrigation infrastructure don’t we look at river infrastructure?
Less river?
Scientists are warning that we can expect a much drier regime. As set out in our report, A future-proofed Basin, as it gets drier an increasing proportion of inflows are required just to cover evaporate losses. This unfortunate reality cannot be denied.
A small reduction in mean rainfall, say, 10% can lead to a 70% reduction in the volume of water available for use. In the short term, the system storages can be run down but, ultimately, either the amount of water for evaporative and other system losses needs to be reduced or the amount used for environmental, irrigation and other purposes cut drastically.
One of the simplest ways to reduce losses is to build a bank or control structure so that water can be kept out of an area and evaporative losses reduced permanently. Another way is to construct a bank across a lake and fill part rather than all of the lake.
Benefits and costs
When resources are scarce, the available water needs to be applied in areas where it can make the greatest contribution. When evaporative losses are reduced, more water is available for all forms of use, including over-bank applications to water-dependent ecosystems on either side of a river. Changes like this do, however, come at a cost. A benefit to one person may come at a cost to others. Nearly every part of a river has people who are sentimentally and/or economically attached to it.
Deciding to close off part of a river system may sound a bit like triage – even if it is man-made. In practice, however, this is really about the allocation and use of scarce resources for maximum benefit. Careful research, analysis and evaluation of trade-offs are necessary.
Indices of environmental and other values must be developed and processes established to assist in deciding which parts of the system to keep and which to let go. Careful community engagement and consultation is essential. At the end of the day, one would expect some parts of the system to be kept inundated no matter how dry it gets, some parts to be watered periodically, some parts to be watered only in very wet years and some parts to never be watered again. Some probably never should have been watered.
Smart management of environmental water
In an environment where there is insufficient water to keep all environmental assets going, the usual recommendation is to ensure that all watering decisions complement one another. Diversity and risk reduction, not more of the same is the way to go. Smart environmental managers must be expected to water some parts well rather than all parts poorly. Like farmers, they need to be able to spit forests into two or three areas and should be required to monitor water use carefully.
Timing is also important. If all environmental allocations are held centrally, however, speedy decision making is problematic. In our view, environmental water use will be much more effective if local managers are allowed to manage and given the responsibility to decide when to use water that has been allocated to them, when to sell it, when to carry it forward and when to buy more.
Strategies still need to be developed and considerable co-ordination is necessary, but if smart outcomes are to be achieved, then innovation must be the name of the game. In this brave new world, we should expect environmental managers to be as smart in the use of techniques and technology as irrigators are.
River height and flow management flexibility
Another issue is the management of river height and flow. In regulated river systems, like the River Murray, river height has been kept constant for many years. Most of this system’s locks and weirs were installed between fifty and one hundred years ago. With a change in management regime, many transitional problems can be expected to emerge. As illustrated by recent decisions to lower the river, acid sulphate soil hot spots may emerge and banks may slump.
Recreation and navigation values and irrigation supply access issues need consideration. Town water supply and sewage treatment arrangements may need a rethink. Careful analysis may suggest that when water supplies and inflow are low, some weirs may be better left open. In places where this is done, new water supply arrangements may need to be put in place. In some parts of the system, for example, we suspect that it may be more efficient to pipe water from the river and abandon some of the channel systems and local wetlands dependent upon water previously supplied from these channels.
Dynamic river salinity management
There is an old saying that the secret to pollution is dilution – but dilution requires water. When demand is seasonal, a much more dynamic approach to salinity management may be possible. If the impacts of river salinity are less in winter than in summer, why not allow river salinity to go up and down? If this happened salinity managers would need to be given incentives to manage river salinity and plan when to release salt into the system – as is done in the Hunter River. These managers also need to be made accountable for the groundwater they use. Each salinity interception scheme could be given an entitlement which requires them to keep use within the volumes of water allocated.
Environmental managers would also need to be brought into the management system. At the moment, there are large volumes of salt lying on the surface of water-dependent ecosystems along the sides of the river. As soon as these floodplains receive water again, large volumes of salt will enter the river.
Where to from here?
The first step in thinking about reconfiguring a river system is to search for opportunities to do this. Given the current state of the River Murray system, we think that this opportunity is worth serious consideration. Having scoped and identified the opportunities to close off wetlands, make lakes smaller etc., the next step is to develop the models and decision making tools to enable rational choices to be made. Armed with such information and tools, the last step is to come up with a suite of recommendations about the nature of changes which if made, would make river operation under a drier regime more effective and efficient.
Given the complexity and sensitivity of this task, it may be wise to appoint an independent person to lead a group of people able to commission research and evaluate opportunities in a rational manner and consult widely about ways to re-configure and operate our rivers and the many ecosystems that lie on either side of their banks. Their brief would be to find ways to get more outcomes from a smaller but better managed river system.
Mike Young, The University of Adelaide,
e-mail: Mike.Young@adelaide.edu.au
Jim McColl, CSIRO Sustainable Ecosystems,
e-mail: Jim.McColl@csiro.au
Acknowledgements
Comments made on earlier drafts by Stuart Bunn, Jim Donaldson, Matthew Durack, Judy Goode, Virginia Hawker, Digby Jacobs, Ian Kowalick, John Radcliffe and Bill Young are acknowledged with appreciation. We also acknowledge the opportunity to discuss this issue with a significant number of irrigators, state administrators and the support of our Project Steering Committee.
References (Access themby clicking on the links embedded in this Droplet.)
A future proofed Basin: A new water management regime for the Murray-Darling Basin
Copyright © 2009 The University of Adelaide.
This work is copyright. It may be reproduced subject to the inclusion of an acknowledgement of its source. Production of Droplets is supported by Land and Water Australia and CSIRO Water for a Healthy Country. Responsibility remains with the authors."
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