[jessewmc]

Yet another perspective: From http://water.usgs.gov/edu/wateruse-total.html in 2010 306 billion gallons of fresh water per day used in the united states. Volume of Lake Superior is very roughly 3,000,000,000,000,000 gallons.

V Lake Superior / (306 * 10^12 * 365) = 26.86 years

About 27 years of entire US water supply assuming no water cycle. Now that I do the math (hopefully I didn't screw it up), I'm not sure that's a big number or a small one actually.

[leojg]

Its big... take in account the inefficient water management that we have and that a martian colony would be numbered in the thousands, at best. This is basically unlimited reserves!