This report is available for viewing in the Alice Springs …

Comment on Todd River dam: It’s all been said before. by Physics Bill.

This report is available for viewing in the Alice Springs collection of the town library.
The report recommends the full (wet) dam option that would permanently flood Tnyere-Akerte. It would be 35 meters high with a spillway 20 m above the riverbed. The report also discusses the empty (dry) dam option starting on page 66 of volume 1.
Both options mitigate the 100 year flood and were roughly equal in cost (~$20M in 1990 dollars).
The empty dam would have a 6.5 meter diameter channel in the bottom to drain at a rate that would not cause the Todd to flood. Both options would trap sediment above them that would have to be moved downstream to keep the riverbed refreshed.
The empty dam option required some extra engineering at an uncertain cost to manage high flow rate (50km/hr) in the 6.5 m diameter channel. The full dam option could be used as a recreation lake or to provide some supplemental drinking water, but there is no further discussion of a recreation lake.
As Erwin noted in his water plan article the “Pan evaporation” is 3 m per year. This means the proposed recreation lake level would decrease an average of 8mm every day there is no runoff. When there is runoff in the 360 km^2 dam catchment the 1.2 km^2 lake would rise 300mm for every mm of runoff.
My recommendation is that the empty dam option be reconsidered. A recreation lake with highly variable lake levels does not seem to me to be much of an advantage.

Recent Comments by Physics Bill

Grand scheme meets small minds
Clarification – the percentages I listed in my previous comment are Yulara percent of the total traffic to Alice and Yulara. Comparing the Yulara to Alice traffic shows a growth in Yulara traffic from 17% of Alice’s traffic to over 50% by 1996-97. It fluctuates between 40% and 65% of Alice’s traffic thru the end of the data set.


Grand scheme meets small minds
@ Alex Nelson (Posted March 29, 2018 at 12:21 pm):
Thanks for the reference.
I was able to find passenger data for 1985-86 to 2010-2011. Yulara is listed as Ayers Rock in the data table. The first few years Yulara has only about 15% of Alice’s passengers, but by 1995-96 Yulara has grown to a third of Alice’s traffic.
The ratio stays around a third to the end of the data set in 2010-2011. I suspect almost all of the Yulara traffic is tourists and that only a few of them visit Alice.


Grand scheme meets small minds
Are the numbers of international and domestic visitors available? I suspect that they will show a dramatic drop around the time the Yulara airport opened (~2000). While the 300,000 passengers a year that fly to Yulara are good for the NT, I suspect most of them bypass Alice Springs.

[ED – Hi Bill, see “Tourism dollars for Alice: not a pretty picture.”]


Offences against the person went up 16% in December
How can there be 680 domestic violence incidents, but only 209 assaults (all categories) in December 2017?
What is the difference between a domestic violence incident and a domestic violence related assault?
Promis reports 209 assaults in Alice Springs December 2017.
From the Alice Springs News Online article “Offenders bailed to ‘country’” posted 15 Feb: “Commander Kershaw says there were 680 domestic violence incidents in Alice alone in December and about 540 in January.”


Offenders bailed to ‘country’: An option, says police
Domestic violence has dramatically increased since Point of Sale Intervention at the bottle shops was suspended.
Domestic violence related assault:
(01/12/2016 – 30/11/2017) = 951 (~79/month)
December 2017 = 680
January 2018 = 540
If the next 10 months continue at the same rate as December and January there will be 7320 assaults – up 770%!
Numbers from NT police web site.


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