1. THE STAFF OF LIFE Water, Earth's most precious resource, serves simultaneously as habitat, nourishment and cleanser. Brazil's Pantanal River, for example, is home to 3,500 species of plants, 400 kinds of fish, 650 bird species, 100 kinds of mammals and 80 types of reptiles. It is not only a vital waterway for man, but an essential filter for the impurities he leaves behind.

2. SOURCE Underground aquifers, dozens of miles deep and hundreds of miles wide, are the Earth's second-largest reserve of fresh water, after ice caps and glaciers. Filled over billions of years, they are today being drained at two to four times their natural recharge rate. In this photo, a team of recreational spelunkers drop into the 160-foot deep Neversink Pit in Alabama, which local cavers have bought to preserve for future generations.

3. SACRED BATH Shamans in Ecuador perform a soul-cleansing ritual at Peguche Falls during the Inti Raymi fiesta, an ancient Incan celebration of the sun. It is believed that water gives a person power to work and the courage to dance for the fiesta.

4. DRIED UP SEABED The Aral Sea has lost two-thirds of its volume because its source rivers were diverted for cotton irrigation during the Soviet era. Once the fourth-largest lake in the world, it is now a dusty graveyard of rusting shipwrecks.

5. DIGGING DEEP More than two billion people worldwide rely on wells for their water. As water tables continue to drop, many of them, like these Kenyan villagers on Pate Island, devote countless hours to collecting and hauling the valuable resource. The pits in this photo, taken less than 300 feet from the ocean's edge, yield a brackish, but drinkable water.

6. SHORT SUPPLY Residents of a slum in a Delhi, India scramble for the water that is delivered to them daily. The camp is home to approximately 4,000 migrant workers, but lacks a clean water supply, so the workers are dependent on public and private trucks to bring it to them.

7. YUCK Students of Miyun elementary school in Beijing discover the dirty condition of a water sample taken from their local reservoir. Twenty-five to thirty-three percent of Chinese do not have access to safe drinking water.

8. FISHING HOLES Ice fishermen work their lines on Russia's Ural River, in the shadow of Lenin Steelworks. Worried that the fish are too contaminated to eat, many of these winter anglers send their catch to distant markets for sale.

9. PIPELINE Because water in Mumbai, India is prohibitively expensive, many residents of this slum rely on leaks found — or created — in the massive tubes that carry water to more affluent neighborhoods. The poor of the city avoid the garbage and human waster surrounding their dwellings by walking on top of the pipelines.

10. FACTORY FILTH Wastewater from the state-owned Lianhua MSG Factory in China's Huai River Basin runs out of a pipe. Lianhua, which means "lotus flower" is largest polluter in the region.

11. DIRTY WATER Foul-smelling water mixed with coal had been running from Kenny Stroud's faucet for more than a decade before clean tap water was finally provided by the city of Rawl, West Virginia. Residents of the town with similar problems blame Massey Energy, a coal mining company for the bad water, saying that the problem, caused by the company's practice of dumping coal slurry into local streams and waterways, has caused numerous health problems. In 2007, Massey settled a $30 million lawsuit filed by the state.

12. DESALINATION Spain's drive to develop its southern coast for tourism has required it to tap the Mediterranean Sea for fresh water. The country's 700 desalination plants produce 800 million gallons yearly.

13. FILTRATION Two Sudanese boys drink with specially fitted plastic tubes provided by the Carter Center to guard against the water-borne larvae which are responsible for guinea worm disease. The program has distributed millions of tubes and has reduced the spread of this debilitating disease by 70 percent.

14. OUTHOUSES The waters of the Niger River Delta are used for defecating, bathing, fishing and garbage. Despite the fact that oil companies have removed more than $400 billion of wealth out of the wetland, local residents have little to show for it.

15. TOILET SOLUTION Children in developing countries are afraid of using outhouses and the like because they are dark and smelly and they fear falling into the hole. For this school in India, WaterAid, a British NGO dedicated to delivering safe domestic water, provided funding to build child-friendly toilets.

16. RESEARCH AND DEVELOPMENT Engineers work at Caroma, an Australian company that is developing improved low-flow toilets. Their product uses only three-quarters of a gallon of water to flush, compared with standard low-flow toilets, which use more than a gallon and a half.

17. SLOW THE MELT The glaciers that provide Europe with drinking water have lost more than half their volume in the last century. In this photo, workers at the Pitztal Glacier ski resort in Austria push a fleece-like blanket down the glacier's slope to protect the snow during the summer months.

18. EMERGENCY SUPPLY Chinese soldiers examine bottled water in Harbin after the city's 3.8 million residents lost access to drinking water for five days due to a chemical plant explosion in 2005. The announcement of water stoppages led to panic buying of water and food, sending prices soaring.

19. SEEDLING The low-cost KB Drip system provides small time farmers in India with the ability to channel irrigated water, thus giving them the opportunity to work more efficiently and lift themselves out of poverty. The project was developed by International Development Enterprises, backed by the New York-based Acumen fund, which recruits machine shops to make the materials and enlists local retailers to distribute them, all for a profit.

20. RING AROUND THE WELL The Chilukwa Primary School in Malawi provides its students with a sound education, but until recently the school had no running water or bathrooms. The Peer Water Exchange (PWX), a platform for crafting local solutions to specific water problems, helped secure funding for a local organization to build a community tap, latrines and bathing facilities.

21. REFRESHING Vietnamese children like Tran Quoc Xu, 11, used to spend a significant portion of their day fetching water. Today, a water system funded by the Blue Planet Run Foundation and PWX means that villagers in Dong Lam hamlet need not travel great distances or pay lots of money for their water.