<p>A man stands on the end of a dock that used to lead to the waters of Lake Mead, the largest artificial reservoir in the U.S., in a 2008 photograph. Below, a picture taken near Hoover Dam shows the lake in 2006. (See <a id="svth" title="another picture of the shrinking lake" href="http://news.nationalgeographic.com/news/2007/08/photogalleries/wip-week40/photo4.html">another picture of the shrinking Lake Mead</a>.)<br><br>A <a id="vi9o" title="hydropower" href="http://environment.nationalgeographic.com/environment/global-warming/hydropower-profile/">hydropower</a> reservoir along the Colorado River, Lake Mead was intended to serve as one of several "water banks" for 30 million people in the arid U.S. Southwest, according to photographer <a id="qoue" title="Jonathan Waterman" href="http://jonathanwaterman.com/">Jonathan Waterman</a>, who took the 2008 shot. But those liquid assets have been quickly disappearing due to drought and increased demand.<br><br>Overall, the decline of Lake Mead may be just a drop in the bucket when it comes to the world's dwindling <a id="c7nm" title="freshwater" href="http://environment.nationalgeographic.com/habitats/freshwater-profile/">freshwater</a> resources.<br><br>With <a id="v6-e" title="World Water Day" href="http://www.worldwaterday2010.info/">World Water Day</a> kicking off on March 22, 2010, United Nations water experts are warning that human activities—especially population growth, industrial pollution, and climate change—are degrading our planet's limited supply of fresh water. (Get <a id="gd7c" title="clean water news." href="http://news.nationalgeographic.com/news/clean_water_crisis.html">news on the global freshwater crisis</a>.)</p>

Dock to Nowhere

A man stands on the end of a dock that used to lead to the waters of Lake Mead, the largest artificial reservoir in the U.S., in a 2008 photograph. Below, a picture taken near Hoover Dam shows the lake in 2006. (See another picture of the shrinking Lake Mead.)

A hydropower reservoir along the Colorado River, Lake Mead was intended to serve as one of several "water banks" for 30 million people in the arid U.S. Southwest, according to photographer Jonathan Waterman, who took the 2008 shot. But those liquid assets have been quickly disappearing due to drought and increased demand.

Overall, the decline of Lake Mead may be just a drop in the bucket when it comes to the world's dwindling freshwater resources.

With World Water Day kicking off on March 22, 2010, United Nations water experts are warning that human activities—especially population growth, industrial pollution, and climate change—are degrading our planet's limited supply of fresh water. (Get news on the global freshwater crisis.)

Photographs by Jon Waterman (top) and Laura Rauch, AP (bottom)

World Water Day Pictures: Epic Disappearing Acts

See before-and-after scenes of a sea vanishing, a lake plummeting, a Swiss glacier retreating, and more—pictures of fresh water on the brink for World Water Day 2010.

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