The Australian government’s new $10 billion, 10 point plan entitled ‘A National Plan for Water Security’ states that there is a need to address “once and for all water over-allocation in the Murray-Darling Basin”. This is point 4 of the plan.
So what does it mean to be “over-allocated”?
According to The Plan “over-allocation is where more entitlements have been issued in a system than can be sustained.”
What does this mean?
According to a recent report ‘Water Use and Regulation’ by the ANZ bank:
“The National Water Commission estimates that as of 205, 1 percent of Australia’s 340 surface management areas and 5 percent of 367 groundwater management areas were over-allocated (that is over 100 percent of sustainable water levels were permanently allocated for extraction and consumption), while another 13 percent of surface water and 23 percent of groundwater areas were ‘highly developed’ (that is 70-100 percent of sustainable water was allocated) putting them at greater risk of temporary over-allocation during dry periods.”
I find the concept that over-allocation means over 100 percent of the water in a system has been allocated unusual and extreme and I have contacted the Nation Water Commission asking for more information and the specific reference. (deleted following comments below from Ian Mott and Wally, see below)
In the relevant document from the National Water Initiative there is no specific definition of ‘over allocation’ and comment is made that each state and territory has used different criteria.***
In the development of ‘Water Allocation and Management Plans’ in Queensland under the Water Act 2000 the arbitrary figure of 30 percent was used; that is if more than 30 percent of a river’s flow is diverted it could be considered over-allocated.*
How much of the Murray Darling Basin’s water is diverted?
Under natural conditions it is estimated that 46 percent of the 24,000 gigalitres that flow into the Murray-Darling Basin is consumed by wetlands and floodplains with the remaining 54 percent flowing out to sea. Now, with all the regulation it is estimated that 11,580 gigalitres, or about 50 percent of the water within the Murray Darling Basin, is diverted for irrigation.**
Based on the estimates in ‘River Losses and End of System Flows’ (MDBC, November 2003, and ignoring the 1,200 gigalitres from Inter-Basin Transfers), it would require that the government buy back about 4,425 gigalitres of water entitlement for the system to be at a 30 percent level of extraction.
If government paid a probably conservative $1,000 per megalitres for permanent entitlements then I estimate they would need about $4.425 billion.
This is an awful lot of money and the government currently only has $3 billion in the budget for buying water entitlements.
Is it worth it? What would be the net benefit of returning the 4,425 gigalitres to the Murray Darling Basin?
The Murray-Darling Basin covers about 14 percent of the land mass of Australia but mean runoff is only about 24,000 gigalitres or 6 percent of the Australia’s total mean annual runoff (Australian Water Resources Assessment 2000, pg 25).
While relatively little water falls within the Basin (6 percent), most of Australia’s water infrastructure has been developed here including the Snowy Mountain scheme build in the 1950s to drought proof the region.
The Murray River has essentially been turned into an irrigation channel with its headwaters part of the Snowy hydroelectricity scheme, four large dams and 13 locks along the way and the system ends in a series of barrages at the so-called Murray mouth.
The Murray River is kept artificially high most of the time as water is moved from the dams which are mostly at the top of the Catchment to irrigation areas downstream and also to meet Adelaide’s water needs.
The Darling is a very different system and less regulated.
In summary, ‘A National Plan for Water Security’ assumes over-allocation in the Murray Darling Basin but does not explain how this was determined and what an acceptable level of extraction might be. Assuming that 30 percent of pre-development flow levels is a reasonable level of extractions, the government would have to buy back about 4,425 gigalitres of water and is likely to cost more than $3 billion.
Buying back this water is likely to significantly impact on agricultural production in the Basin and the rural communities in irrigation areas.
There are already significant environmental flow allocations for the Murray River. Given the Murray River is already a highly regulated and somewhat artificial river system I doubt that the environmental benefit from the return of additional water would be significant. What would the environmental benefits be for the Darling River system?
This is the second in a series of posts on ‘A National Plan for Water Security’, Part 1 is here: http://www.jennifermarohasy.com/blog/archives/001859.html
* I can’t find a good reference or link for this, Luke can you help?
** Based on ‘River Losses and End of System Flows’, published by the Murray Darling Basin Commission, November 2003. Can someone find the document on the internet for me?
***Changes made to this post at 12noon on Friday 2nd February.