2007-06-22<BR>　　St. Clair River, Michigan or Ontario, 2002<BR>　　Photograph by Jay Dickman<BR>　　Falling water levels expose a sandbar in the Great Lakes' St. Clair River. <BR>　　The five Great Lakes, and the rivers, channels, and lesser lakes that connect to them, hold a fifth of the world's surface fresh water. But below-average precipitation, increased evaporation due to above-average temperatures, and mounting water consumption is driving water levels here to record lows. <BR>　　<BR>　　(Text adapted from and photo shot on assignment for, but not published in, "Down the Drain: The Incredible Shrinking Great Lakes, " September 2002, National Geographic magazine) <BR>　　<BR>　　<BR>　　在五大湖区的圣克莱尔河，一块沙洲随着水位的下降显露出来。<BR>　　<BR>　　五大湖区，以及所属的河流，渠道和一些与其相通的小湖，拥有世界五分之一的地表淡水。但是低于平均水平的降水量，因高于平均水平的温度而升高的蒸发量，以及日益增加的耗水量使得这里的水位创出新低。<BR>　　<BR><BR><IMG src="http://lava.nationalgeographic.com/pod/pictures/lg_wallpaper/MM6801_0026.jpg">
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