THE Murray-Darling Basin Plan can’t deliver anything tangible and meaningful for communities, industry or the environment while its water sharing plans are based on averages.
Averages are a meaningless concept in the real world given the highly variable nature of Australian rainfall.
The draft plan identifies 10,873 gigalitres as the maximum amount of water on water that can be “sustainably” extracted from the Basin on average each year.
But this number is a product of politics, not science, and has no real meaning in terms of river health.
The draft plan acknowledges the highly variable nature of the system – Schedule 1 explains annual inflows to the Basin in the past 114 years have ranged from a high of 117,907GL in 1956 to only 6740 GL in 2006 – and
notes this natural variability of flows is important to Basin ecology.
Yet this variability is then ignored in arriving at one number: the sustainable diversion limit of 10,873GL based on a calculated average inflow to the entire Murray Darling Basin of 31,599GL.
The draft plan gives the impression there has been gross over-allocation of this average inflow by claiming on average only about 12,000GL reaches the Murray Mouth – hinting that much more water should flow out the Murray ‘s Mouth to the sea.
But not only is an average value in such a naturally variable system somewhat meaningless, the value of 12,000GL is misleading because construction of the 7.6 kilometres of barrages across the Murray River’s estuary (just upstream of the mouth) in the 1930s has in itself reduced flows to the Murray Mouth by 75 per cent – additional to any reduction from upstream diversions for irrigation.
Indeed this derived average value of 12,000GL would be much larger if it was measured at Wellington in South Australia where the Murray River enters the terminal coastal lakes, now known as the Lower Lakes.
The reality is not all water flowing into the Murray-Darling Basin should be expected to reaches the Murray River, let alone its mouth.
For example, the Lachlan River is part of the Murray Darling Basin but in most years contributes no water to the Murray River because it naturally flows into a swamp.
British explorer Charles Sturt eloquently explained the nature of the system decades before the development of any irrigation writing that Australian rivers tend to “naturally fail before they reach the coast, and exhaust themselves in marshes or lakes; or reach it so weakened as to be unable to preserve clear or navigable mouths, or to remove the sand banks that the tides throw up before them”.
The draft plan also fails to acknowledge the role of storages in providing water during drought. In fact as a consequence of the increase in storage capacity (i.e., dams) over the last 50 years, the water level in the Murray River is unnaturally high for much of the length of the river, most of the time.
But this reality is ignored because it makes a mockery of the concept of over-allocation that is an assumption underpinning the entire rationale for the Water Act under which the plan has been drawn up.
The draft plan reduces the concept of river health to a single number – the sustainable diversion limit of 10,873GL – but it is unclear how deriving this number from meaningless averages in a highly variable system will benefit the environments of the Murray Darling.
Indeed, it will do nothing to solve the problems of the Lower Lakes during drought – problems that are a consequence of the 7.6km of concrete barrage.
This new sustainable diversion limit is meant to mean more freshwater for these lakes but it is seawater, not freshwater, that the lakes really need if they are to be returned to ecological health and the Murray River ‘s estuary restored. Indeed how can the new draft plan purport to be about delivering an improved Murray River environment when it totally ignores the need to restore the Murray River ‘s estuary?
The draft plan is essentially a political document reflecting a popular myth in urban Australia that the ailing health of the system has been caused by greedy irrigators taking water from the river.
In arriving at a single number of 10,873GL and then extrapolating to suggest that this means an additional 2750GL must be taken from irrigators, the draft plan reinforces the false perception that irrigators always take a set volume of water from the system.
In reality the amount of water diverted for irrigation has always been highly variable with most irrigators receiving a small fraction of their licence entitlement during periods of drought.
Development of the draft plan was overseen by politicians; in particular Murray Darling Basin Authority boss and Labor party veteran Craig Knowles.
Perhaps it’s now time different politicians got more involved, in particular that NSW Deputy Premier Andrew Stoner deliver on his promise in last week’s The Land and tosses the whole nonsense document out.
First published in The Land on December 1, page 8 under the title ‘Averages Meaningless to Murray’.