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)
The Vanishing Snows of Kilimanjaro
Africa's highest point may soon reach a new low if the glaciers atop Tanzania's famous Kilimanjaro (seen in 2009, top, and 2003) disappear due to climate change, experts say.
Research released in 2007 suggested that the fabled Kilimanjaro snows may not succumb to global warming as quickly as scientists had feared. The same findings had linked the loss of Kilimanjaro's ice fields to decreased precipitation in Africa—something the organizers of World Water Day warn could affect human health on the continent due to limited access to fresh water.
Meanwhile, Kilimanjaro's ice "continues to diminish right on schedule for disappearing, unfortunately, in the next couple of decades," glaciologist Lonnie Thompson, at Ohio State University in Columbus, said in November 2009. (Read about the world's melting glaciers in National Geographic magazine.)
Photographs by Beverly Joubert (top) and David Pluth (bottom), National Geographic
Hell or High Water
You might call it an act of God: A severe drought in Venezuela has exposed an 82-foot-tall (25-meter-tall) church—pictured in February 2010 (top) and in January 2009—that had been inundated to create a reservoir for a hydroelectric dam built in 1985. (See more pictures of the exposed church.)
Water shortages due to drought mean that the plant is currently operating at just 7 percent capacity, according to the Reuters news service.
The church is now an ominous symbol of energy shortages in the country, which gets around 68 percent of its power from hydroelectricity, Reuters reported. The droughts spurred Venezuelan President Hugo Chavez to declare an energy emergency in February.
Photographs by Jorge Silva, Reuters (top) and from Diario La Nacion via Reuters (bottom)
Shrinking Swiss Glacier
As the world warms, even a Swiss glacier might not be able to stand the test of time. The Rhone glacier in the Swiss Alps (seen in September 2004, top, and August 2008) is shrinking fast due to rising temperatures in the region.
Climate change experts predict that heat waves will sweep through many parts of Europe by 2040, according to the Met Office's Hadley Centre, a U.K. climate-research center—creating serious impacts on freshwater resources.
The Rhone glacier's runoff, for instance, is the main water source for Switzerland's Lake Geneva, about 96 miles (155 kilometers) downstream. (Related: "Alps Glaciers Gone by 2050, Expert Says.")
The glacier is also a wellspring of tourism revenue for nearby towns, which are going to "heroic lengths" to protect the ice during hotter months, according to NASA's Earth Observatory. For instance, townspeople annually cover the front section of ice with insulating blankets to try to slow summertime melt.
Photographs by Arnd Wiegmann, Reuters
Talk about a sea change: From 2006 (bottom) to 2009, Central Asia's vast Aral Sea dramatically retreated, with its eastern section losing about 80 percent of its water in just four years, as seen in satellite imagery.
The immense body of water, which straddles Uzbekistan and Kazakhstan (map), was once the world's fourth largest freshwater lake. But in the past 30 years, 60 percent of the lake has been diverted to irrigate crops of water-strapped farmers, according to NASA's Earth Observatory.
With little government attention, it's likely that the southern section of the Aral Sea may soon be gone for good, experts say.