Dams
I stumbled across this little pearl of knowledge in my travels today:
Water impoundment by dams in the Northern Hemisphere is now so great that it has caused measurable geodynamic changes in the Earth’s rotation and gravitational field (Chao, 1995).
CHAO, B. F. (1995). Anthropogenic impact on global geodynamics due to reservoir water impoundment. Geophysical Research Letters 22, 3529–3532.
October 31st, 2007 at 10:17 am
How do they prove that? Especially since solid water on land melting would/should have a greater impact than impounded water. The earth is a very slow moving system would 50 to 100 years of water impounding have a noticeable effect? How have they measured a baseline? how have they removed interference from other factors in their calculations? many questions but it sounds like an interesting paper
October 31st, 2007 at 12:01 pm
Yep, when they were building the Three Gorges Dam, someone noticed a bit of a wobble in the earth as the water accumulated in the reservoir. If you really want to get your hackles up over North America’s abuse of river systems, read Cadillac Desert by Marc Reisner. I’m getting all riled up just thinking about it…
October 31st, 2007 at 9:06 pm
timtim, you’re the reason I provided the full reference. Why don’t you read it and give us a summary?
November 1st, 2007 at 10:09 pm
http://www.unsw.edu.au/news/pad/articles/2007/oct/Macquarie_Marshes.html
November 2nd, 2007 at 9:20 am
hey mate do you have access to those articles? If so could you email me a PDF or I can look at a hard copy on the weekend if you have it.
November 6th, 2007 at 8:20 am
So there are several factors that affect the earth’s gravity and rotation and it does make sense. The effects are cumulatively small but not proportionally insignificant when compared with the natural variation in the system. Basically water is impounded near people, more people live in the most habitable areas and water when it is impounded acts as a point like the weights on a car wheel.
Most people in the world live in the northern hemisphere and closer to the temperate latitudes meaning the weight distribution of stored water is skewed to the north and the point load is further from the rotational axis. So like a pirouette weight further from the rotational axis will have a profound effect on the speed of rotation.
Out of all this day length can be affected by a very small amount and axial shift can be affected by a very small amount. Both are proportionally large when compared with overall change.
November 6th, 2007 at 9:49 pm
“not proportionally insignificant”
man, don’t you love scientific writing - so accessible!
November 8th, 2007 at 12:24 pm
I felt sleepy reading the thing. I’m glad I’ve not had to do too many lit reviews
November 8th, 2007 at 1:42 pm
it is not disproportionately significant either… and if it wobbles too much, won’t the water spill out anyway???
November 9th, 2007 at 3:50 pm
only if you can wobble it back and forth. I wonder if they get a tidal type effect in some really big dams or if the net flow downstream negates any possible influence
November 13th, 2007 at 1:12 pm
yawn!!!!!