Water

By the end of the recent state election in Queensland, the Labor Party was proposing not one, but five new dams and the the Coalition a whooping eight new dams. The Wyaralong dam is being planned for a catchment just south of Brisbane and west of the Gold Coast in the Beaudesert Shire. Occasional responder at this blog Sylvia Else, has done some research, and claims even desalinated water would be cheaper than water from the Wyaralong Dam:

Hi Jennifer,

I’ve been puzzling over the proposed Wyaralong dam. Given the government’s own cost estimates and the estimated yield, and using an interest rate of 7.5% and inflation rate of 3%, I cannot get the cost of the raw, i.e.
unfiltered, water below $1 per kilolitre, even when I assume a life of 100 years for the dam. I don’t know how much it costs to filter water, but Sydney Water charges 46 cents per kilolitre less for unfiltered water, so filtering is presumably reasonably costly.

This appears to mean that bulk filtered water from Wyaralong dam will be more expensive than desalinated water. With Perth’s desalinator capital and running costs, I get a bulk water cost of $1.02 per kilolitre.

It’s true that the only place one can desalinate seawater is on the coast, but it appears that the government’s intention is that all of the water supply systems should be connected together in a network, so desalinated water could be distributed to anywhere that the Wyaralong dam could serve.

So why build the dam? It seems to make no economic sense, even if the wished for rainfall (based on the next 100 years being like the last) appears.

There was a line in the Hitch-Hikers’ Guide to the Galaxy. When asked why it was necessary to build a by-pass over the top of Arthur Dent’s house, the council official’s reply was “What do you mean, why has it got to be built? It’s a by-pass. You’ve got to build by-passes.”

May be that’s the reasoning being used here.

Regards
Sylvia Else

Roger Kalla, a member of this blog community, has just had a piece published on water recycling, including for snow making, at OLO. It includes comment that:

“Up in the Victorian Alps there is truly “no business like snow business”. It literally forms the semi-solid foundation on which the whole thriving multimillion dollar tourism economy rests. But it is a slippery slope in years of snow drought. Any skiing in the future in ski resorts like Mt Buller is increasingly likely to be done on recycled sewerage containing artificially added bacteria or bacterial products.

Most skiers and visitors to the snow fields surely don’t mind. The snow looks real, feels real, and probably tastes real. However for the environmental sensitive skier there perhaps should be warnings on the slopes pointing out that the snow is artificial and an ingredient list of the “snow” enclosed on the lift ticket.”

Read the full article by clicking here.

It has been suggested that before irrigation runoff into the Macquarie Marshes was 460,000 megalitres and that this has been reduced to 395,000ml by irrigation.

But Ian Mott has argued that pre-settlement runoff into the marshes would have been much less than 460,000ml and most likely less than 395,000ml because much of the upper catchment was once forested. Because it has since been cleared for pasture, runoff would have substantially increased.

Yet the opposite appears to be the case.

In an earlier thread Chris Hogendyk expained that: “Inflows to Burrendong (on the catchment of the Macquarie) for the 68 months from December 2000 to July 2006 was approximately 1700 GL which is the same as the driest similar period on record that occurred from December 1934 to July 1940. The next driest period was December 1903 to July 1909 that received approximately 1950 GL.

“The first data set are actual observations whilst the latter two are modelled. Out of interest, for every 10 megalitres that is captured by the dam, 4 megalitres come into the system as down stream tributaries.”

Interestingly rainfall history as plotted by Warwick Hughes suggests that it was drier during the late 1930s.

This is Warwicks comment on the charts: “These show you some rainfall history for the region from the Bureau of Metereology high quality rain dataset and you can see the obvious cycles in all charts.

“Trangie data is the closest HQ station to the Macquarie Marshes and it shows that in the recent past conditions were similar to dry times times in the 1990’s and 1980’s, if you go back to the 1960’s rainfall was obviously less and even lower in the late 1930’s thru 40’s and earlier again WWI years into the 1920’s look the driest of all.

“The other graphic, also of HQ data, from Mudgee and Bathurst, could be a fair proxy for long term trends higher in the catchment.”

So it has been dry, but not that dry, and with fewer trees, why have inflows been so low lately?

On Monday I posted a graph of rainfall history and suggested that it indicated south east Queensland was not experiencing the worst drought in 100 years – that the current dry spell is not unusual in the scheme of things.

I was surprised how many comments in the thread following the post, and also in the many emails I received, were supportive of the notion that this is a worst drought ever.

Some argued that I didn’t understand definitions of drought and that a drought could simply be a result of too many people squashed into a region without the infrastructure to supply adequate water. Comment was also made that it would be interesting to see the rainfall history for the catchment averaged over 10 years.

Warwick Hughes has sent me the following graph, showing the rainfall history averaged over 10 years:

Mr Beattie has been reported in the Courier Mail stating that:

“Rainfall in the region has been well below average for the past six years and in fact it is the worst 10-year period in history,” he said. “It has been dry after dry, year after year, which has led to major storage deficits in our dams.”

Looking at the above graph Beattie may be technically correct, we may have had the worst 10-year period in recorded history, and those who want to define drought based on ‘supply’ rather than ‘rainfall’ may also be correct because we have never had so many people living in south east Queensland and probably never as many trees growing in the catchment.

But the above graph, and the graph posted on Monday, does indicate that south east Queensland has experienced comparative periods of low rainfall during the 1920s and 1940s. The current dry period is not unusual in the scheme of things.

My point is that: If we can not reconcile ourselves with our history, how can we hope to prepare for the future? It is important we understand what is special about this drought.

If we could perhaps start to acnowledge that rainfall has not been exceptionally low, we might, for example, be able to more clearly focus on other variables, including population.

There is also the issue of tree cover. A heavily timbered catchment generally produces less runoff. Page 7 of yesterday’s The Land reports Malcolm Turnbull, federal parliamentary secretary for water, explaining that the West Australian Water Corporation is thinning catchment forestry to increase run off by 6,000 megalitres a year. Mr Turnbull said the method could deliver “new water” at about 20c/kilolitre – far cheaper than piping or desalination.

I am not necessarily advocating tree clearing in the Wivenhoe catchment, but rather my issue is that here in Queensland, we tend to invoke ‘exceptional circumstances’ whenever there is a flood or a drought rather than taking a more evidence-based, and dare I suggest, more responsible approach.

The most severe natural disaster in the history of South Australia will be commemorated this Sunday with the launch of the 1956 River Murray Flood 50th Anniversary Exhibition in Renmark.

Read more here.