World's Dirtiest Rivers and Lakes

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Pink Chemicals Enter Yellow River From Drainage Pipe Photo
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This 3,400 mile-long Yellow River in China is frequently contaminated by chemical spills, and frequent diversions and damming, which causes the Yellow to often run dry and sometimes even turn red. 1/3 of the river is unusable, but this doesn't seem to be slowing things down as the river is used to provide water for millions of people in China, whose expanding cities are another reason the river is contaminated.

Image via: Getty Images - ChinaFoto Press