Perhaps now with al the talk about Climate change we can shift to a slightly different tact and talk about Climate Modification. The issue is really the unequal and imperfect distribution of rainfall. Moving it in large clocks is an idea but creating ways to move it in aqueducts or even undersea aqueducts might be more useful and practical in the long run.
Gettting it to rain in the right places might turn out to be a much more interesting problem.
Evaluating this as an engineering possibility was actually one of the long questions in the Oxbridge A-level physics examinations in the UK - circa 1978 / 1979 I do believe. ...One of the ones I answered. Successfully appparently. The Nuffield New Physics A-Levels for University entrance - made us think like engineers. Good stuff. Not so sure I could pass now.
Conservation and recovery tricks are not worthwhile for places thatr have no rainfal to begin with.
It seems to me that the most cost effective method of transport could include an underwater insulation blanket, which would also keep the freshwater captive for recovery at the destination, reducing the amount of structure needed to use the water at the destination.
I also see the great challenge in that we have an excess of flood water and a drought at the same time. How about a huge pumping system to transfer the floodwaters to some of the relatively vacant land towards the west, so that it can replenish the ater table. That would solve the problem of cleaning flood water, and remove the cleaning task as well as the distribution challenge.
The huge challenge is to find an economical way to move a cubic mile of water a thousand miles every day without creating a huge negative environmental impact. The positive impact of preventing floods would be fairly easy to see, the other effects are probably less well understood. Next is the question about the building of a 100 foot diameter acquaduct from the Mississippi river to New Mexico. That would be a challenge. OF course, to prevent flooding, it will need to take water from farther upstream, making the aquaduct even longer. What would it take to simulate the aquaduct?
Also worth looking at the systems approach in handling rainwater, which is a valuable resource that current practice tries to get rid of as quickly as possible. Seems like a big part of the problem is the following typical sequence:
Get some land
Log off the timber and clear it, pave large areas, build large roof areas, plant grass lawns instead of vegetation that retains water
Channel roof gutters and runoff to drains, resulting in increased fast runoff
Complain about increased flooding
You might be interested in some books such as "Rainwater Harvesting for Drylands and Beyond" (Brad Lancaster) and the forthcoming book on rainwater harvesting by Art Ludwig. The first book could be considered a bit preachy but has some very interesting ideas about system design.
Jim B., nice post. Additionally, it'd be great to see us work on a reservoir system in the Midwest. While states such as Georgia and Texas have been experiencing severe drought, it frustrates me to see states along the Mississippi flood plain get consistently flooded year after year. Farmland, towns, etc... destroyed by the swelling river. I can imagine a capture system that diverts these flood waters at predetermined locales for California aqueduct style rerouting to areas that consistently are in need.
It is clear that water can be moved as icebergs, though the costs reported are misleading since there is no detail about how the iceberg will be tapped when it is at its destination. This might not be insurmountable, but it might make the iceberg a less viable choice except for special destinations where there are no other options.
It has already been proven that water can be effectively moved in aquaducts and these are more readily coupled into irrigation water systems as well as municipal systems. We would do better to look at distributing water on a continental basis in North America. This would be a practical infrastructure project and would involve no advanced knowledge or simulations.
The California aquaduct built in the early 1960s demonstrated the enormous productivity that can result from relatively primitive water engineering.
On an ongoing basis, the Great Lakes and many Canadian sources could be used in a continental water management system. This could change the productivity of massive Western land areas. The special benefit would be that it could enable establishing standing forests of sufficient extent to serve as 'carbon' capture and sequestration without sacrificing the economic backbone of our industrial economy. Other measures would still be important, but it would no longer be necessary rail against coal fired power plants or oil sands processing.
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