JF Ptak Science Books Post 2277
If you haven't thought of this statement before, if you haven't tried to visualize all of the Earth's sources of water all drawn out and up and somehow gathered into a Superman-controlled sphere of no structure, then this image would be very surprising--it was to me.
The image comes from the United States Geological Survey website1, and shows three spheres on an Earth emptied of its oceans and lakes and rivers and ponds and creeks and everything, all sources of water, and depicts in descending order a sphere containing all of that water, followed by the Earth's liquid fresh water, and lastly in the tiny sphere all of the water in lakes and rivers.
The first and largest sphere is actually enormous, though it doesn't look so when compared to the size of the Earth--it is 860 miles in diameter and holds 332 million cubic miles of water, or about 35x1019 gallons. I do not now if the living beings in the water were figured into these calculations or what that might have looked like. ("The sphere includes all the water in the oceans, ice caps, lakes, and rivers, as well as groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.")
The next sphere is a deeper wake-up call--it represents all of our liquid fresh water ("groundwater, lakes, swamp water, and rivers"), and forms a magical sphere of about 2.5 million cubic miles, about 170 miles in diameter, or about 1% of the total volume of the great sphere.
The last sphere--the tiny blue dot just south of Sphere Two--is the "one represents fresh water in all the lakes and rivers on the planet, and most of the water people and life of earth need every day comes from these surface-water sources", with a volume of 22,339 cubic miles, and a diameter of about 35 miles, or the distance from D.C. to Baltimore.
I've never seen this image before, and I find it remarkable.
If you follow the link to the USGS website, you can also see a breakdown of all of these numbers, as well as a final sphere with ALL of the water on Earth, though I don't think you can really tell the difference between the first spehere and the super sphere.
1. And full credit where credit is due: "Howard Perlman, USGS; globe illustration by Jack Cook, Woods Hole Oceanographic Institution (©); Adam Nieman.
Data source: Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York)."