Snow job on the Snowy River

Where there is an annual rainfall of 700mm a forest will use 650mm while 50mm is runoff. If you clear that forest to pasture and, assuming it is not overgrazed, it will use 545mm of rain with 155mm of runoff, an increase in yield of 210 per cent. So when we look at the catchment below the dams and above the state border we find 1/3rd uncleared land that produces 100 per cent of pre-settlement water yield and 2/3rds cleared land that produces 310 per cent of pre-settlement water yield. And this means that the current runoff of 804,000Ml represents (1x 0.333 + 3.1 x 0.666 = 2.4) 2.4 times the original pre-settlement flows.

Hence, the total pre-settlement flow from both cleared and uncleared land was 335,000Ml while the cleared land now delivers an additional 469,000Ml to the Victorian part of the river.

This tells us that the original pre-settlement flows at the mouth of the Snowy River consisted of; 863,000Ml from the Victorian portion; 335,000Ml from the NSW portion below the dams; and 513,000Ml from above the dams, for a total flow of 1.711 million Ml.

And that means that the current mean annual flow of 1.644 million Ml is actually 96 per cent of the pre-settlement flow. In effect, all but 44,000Ml of the 513,000Ml that is diverted from the Snowy to the Murray is already compensated for by the increased runoff from clearing in the NSW portion.

But the downstream observers in Victoria only have visual and anecdotal references to river flows that have occurred after the upstream clearing activity has increased flows. And it is this man-made increase in river flows that they are now seeking to convert to some sort of baseline for an environmental duty of care to minimise harm.

The facts are that a 4 per cent reduction in river flows is almost statistically irrelevant in terms of the normal range of variation in rainfall and runoff.

This is not to say that the 30 to 40km of river below the dam is not significantly diminished, it obviously is. But pouring $50 million worth of valuable water into the ocean is a very silly, indeed, incompetent way of fixing the problem. There is a much better way - based on the fact that the one type of water use that is most suited to recycling is water used for environmental flows.

The Snowy River itself does a great deal to assist in the recycling of its environmental flows. It traces a large, 95km, bend in the section concerned that ends only 27km away from where it starts. So the construction of a short pipeline and pumping system would enable the release of just a single day’s worth of environmental flow which could then be pumped back to the starting point (recycled) to do the same job each day for the next 364 days each year.

This would take place before the steep drop onto the Victorian lowlands and the countryside that the pipeline would need to cross is already cleared with comparatively mild undulation that is well suited to pumping and syphoning.

The key to the feasibility of this sort of recycling of environmental flows is; can we pump a megalitre of water along a 27km pipe with modest head for less than the price that a farmer would pay for the same megalitre? Clearly, the answer is an unambiguous “Yes”.

Adelaide pumps its water 170km from the Murray River, and over a hill, presumably at an acceptable wholesale price.

Farmers in the Brisbane Valley are eager to pay for recycled Brisbane sewerage that will be pumped more than 60km. The plan to reintroduce recycled water into Wivenhoe Dam will involve a lift of more than 100 metres and more than 40km of pipeline and be reintroduced to the urban water system at a profitable margin on a wholesale price of $170 per Ml.

So even if there was a sound case for restoring flows to the Snowy River then taking good water out of the dams is not the best option. The Greens’ target of 330,000Ml in water savings could be ploughed back into more production that will inject $132 million into towns on the Murray each year. A modest pumping load of 100Ml a day would deliver 36,500Ml of river flow to the actual section of river that needs it while leaving 36,400Ml for farmers to add $15 million worth of crop value to the remainder.

For the moment, the most inefficient water users, and those most reluctant to adopt new ideas, technology and innovations, are the Green movement and their captive departmental minions. Unlike sewerage or storm water recycling, water that is released for environmental flows needs no expensive processing to enable it to be used again, and again. And this capacity for multiple recycling gives it an entire order of magnitude greater priority than all other water efficiency options. We all need to get a lot smarter with our use of water but our self appointed environmental guardians have a lot further to go than anyone else.