爱华网By Brett Israel
地球上有多少水？
由布雷特·以色列（Brett Israel）撰写
2010年09月09日下午04:02 ET
If Earth was the size of a basketball, all of its water would fit into a ping pong ball.
如果地球是一个篮球大小，就可以所有的水可以注进一个乒乓球。
地球上有多少水？据美国地质调查局最近的一项研究，大约为3.26亿立方英里（13.32亿立方千米）。约72％的地球被水遮盖着，可是97％的水是含盐的海水，不适合饮用。
"There's not a lot of water on Earth at all," said David Gallo, an oceanographer at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts.“在地球上必竟没有很多水”，马萨诸塞州伍兹霍尔海洋学研究所（WHOI）的海洋学家大卫·盖洛（David Gallo）说。
Oceans create a water layer spanning 15,000 miles (24,000 kilometers) across the planet at an average depth of more than 2 miles (3.2 km). If you poured all of the world's water on the United States and could contain it, you'd create a lake 90 miles (145 km) deep.海洋在地球上创建了一个横跨15,000英里（24,000公里），平均深度超过2英里（3.2公里）的水层。如果把所有世界的水都灌进美国，加以围住，就可以建成一个深90英里（145公里）的湖。
This seems, and looks, like a lot of water, Gallo told Life's Little Mysteries, but looks can be deceiving.看起来地球似乎有着大量的水，盖洛告诉《生活中的小秘密》，然而其实这可能是欺骗。
If the Earth was an apple, Gallo said, the water layer would be thinner than the fruit's skin.盖洛说，如果地球是一只苹果，水层比苹果皮还要薄。
The Earth's freshwater is even rarer.地球上的淡水更为稀少。
"For humanity to thrive, or even exist, we need to sprinkle that teeny bit of fresh water in the right places, at the right times and in just the right amounts," Gallo said.盖洛说：“对于人类的繁荣，甚至他们的存在，我们需要在正确的地方，在适当的时间，和以刚好合适的数量提供所需要的淡水。”
Here's how Earth's freshwater is spread around the globe:这里是地球上的淡水在各处的分布：
70 percent of freshwater is locked in ice caps70％的淡水被锁定在冰盖里。
Less than 1 percent of the world's freshwater is readily accessible不到1％的世界淡水是容易获取的。
6 countries (Brazil, Russia, Canada, Indonesia, China and Colombia) have 50 percent of the world's freshwater reserves6个国家（巴西、俄罗斯、加拿大、印度尼西亚、中国和哥伦比亚），占有了世界淡水储量的50％.
One-third of the world's population lives in "water-stressed" countries, defined as a country’s ratio of water consumption to water availability. Countries labeled as moderate to high stress consume 20 percent more water than their available supply.世界上三分之一的人口生活在“用水紧张”的国家，“用水紧张”的程度用耗水量与水资源可利用量的比值来衡量。把一些国家标定为中度到高度“用水紧张”是它们消耗了超过可供应水量的20％以上。
There is much more freshwater stored in the ground than there is in liquid form on the surface, according to the USGS.根据美国地质调查局，更多的淡水储存在地下，其数量多于在地球表面上以液体形式所呈现的水。
