March 22, is World Water Day, an event established by the United Nations in 1993 to highlight the challenges associated with this precious resource. Each year has a theme, and this year's is "Water for Cities: Responding to the Urban Challenge." The UN estimates that more than one in six people worldwide lack access to 20-50 liters (5-13 gallons) of safe freshwater a day to ensure their basic needs for drinking, cooking, and cleaning. And as the world's population grows beyond 7 billion, clean water is growing scarcer in densely populated areas as well as in remote villages. Collected here are recent images showing water in our lives -- how we use it, abuse it, and depend on it.
A journalist takes a sample of polluted red-colored water in the Jianhe River in Luoyang, Henan province, China, on December 13, 2011. According to local media, the sources of the pollution were two illegal chemical plants discharging their production waste water into the rain sewer pipes.
Very low water in El Atazar's reservoir near El Berrueco in Madrid, on March 16, 2012. Spanish farmers are already on drought alert after the country's driest winter in 70 years. Spaniards emerged from their usual choking summer last year gasping for rain, but over the past three winter months Spain has had average precipitation of just 55 litres per square meter, far below the average of 200 litres. The latest official drought report on February 22 said Spain's reservoirs were only two-thirds full, meaning less water for the fields where crops grow and animals graze
(Pierre-Philippe Marcou/AFP/Getty Images)
Ice chunks break off the Perito Moreno glacier near the city of El Calafate in the Patagonian province of Santa Cruz, Argentina, on March 2, 2012. As Perito Moreno moves forward, it cuts off a river feeding the lake. Water builds up pressure and slowly undermines the ice, forming a tunnel until ice comes tumbling down. The phenomenon repeats itself at irregular intervals, with the last major ice falls occurring in 2008.
Workers stand in a new addition to the massive underground deep drainage tunnel system in Mexico City, on March 10, 2012. Mexico's President Felipe Calderon was on hand Saturday to inaugurate the new addition aimed at protecting the metropolitan city and its surrounding areas from flooding.
(AP Photo/Marco Ugarte)
A 70-year-old sunken cemetery emerged after Jablanicko lake dried up near Jablanica, Bosnia and Herzegovina, on February 1, 2012. The dams on the Neretva river near the lake feed a system that normally produces an average of 2,000 megawatt-hours of electricity per year, but the drought that began in August has shrunk output to just a quarter of that amount.
A worker looks at a photographer from the door of a factory that manufactures screws and nuts, next to a polluted river in Jiaxing, Zhejiang province, China, on March 15, 2012. China's continuing reliance on heavy industry meant it failed to meet its own targets for cleaning its air and water in 2011.
An Indian technician watches the production line at the quality check division of the Aava Natural Mineral Water plant in Ahmedabad, India, on March 20, 2012. Aava Natural Mineral Water plant is one of the largest manufacturers of natural mineral Water in India, producing more than 1,500,000 bottles a day.
(Sam Panthaky/AFP/Getty Images)
Red polluted water flows from a sewer into the Jian River in Luoyang, north China's Henan province, on December 13, 2011. According to local media, the sources of the pollution were two illegal chemical plants discharging their production waste water into the rain sewer pipes. Authorities said they were working to shut them down and disassemble the workshops' machinery.
Firefighters pour water into villagers' barrels at Xiliu village along Liujiang River in Liuzhou, Guangxi Zhuang autonomous region, China, on February 2, 2012. The official probe into an incident which resulted in cadmium polluting a South China river is making progress and local police have detained eight executives from two companies that are suspected of waste dumping, Xinhua News Agency reported.
Kimberlie McEvoy collects some of her well water as it comes from her kitchen sink at her home in Evans City, Pennsylvania, on February 23, 2012. McEvoy is one of at least 10 households in western Pennsylvania that fears their drinking water has been ruined by nearby natural gas drilling. State officials say tests don't show that. Residents say Rex Energy Corp. has sent letters notifying them it will no longer deliver drinking water to the households after February 29.
(AP Photo/Keith Srakocic)
A penguin has oil washed off by staff at the Tauranga Wastewater Treatment Wildlife Facility in Tauranga, New Zealand, on October 18, 2011. Salvage crews were pumping oil off the Rena, a stranded cargo ship, in an effort to remove as much as possible before bad weather broke the vessel apart. Over 300 tons of oil leaked from Rena since it hit the reef on October 5, 2011.
(Hannah Johnston/Getty Images)
Water from a leaky fire hose rains down on neighborhood residents as they attempt to put out a fire that had already burned dozens of homes, in the New Building slum neighborhood in central Malabo, Equatorial Guinea, on January 23, 2012. As firefighters struggled to get enough water pressure to make their firehoses work, residents fought the fire with buckets of waste water and used mallets to tear down homes in the fire's path.
(AP Photo/Rebecca Blackwell)
Guests enjoy thermal water in an outdoor pool of Szechenyi Thermal Baths during the 5th annual "Night of Baths" in Budapest, Hungary, on March 11, 2012. Following the pattern of the Night of Museums, five thermal baths of Budapest were open through the night to receive guests with various programs to draw attention of the public to advantages of visiting baths.
(AP Photo/MTI, Balazs Mohai)
A church drowned by a tailing pond of a copper mine of Rosia Poieni next to Lupsa village, 460 km west from Bucharest, Romania, on September 20, 2011. The former village of Geamana was engulfed by copper exploitation residues years ago. The tailing pond has a surface of around 250 acres, filled with millions of tons of heavy polluted waste.
(Daniel Mihailescu/AFP/Getty Images)
A therapist from the Gezenguz (Rascal) Foundation works with an infant during an underwater nerve therapy session in Budapest, on October 27, 2011. Infants and children who have birth injuries and congenital developmental conditions or diseases seek rehabilitation at the foundation.
Water contaminated with Polyaluminium Chloride flows through the Nuomitan power station to dilute the cadmium-polluted water in the Longjiang river, in Liuzhou, southwest China's Guangxi province, on January 30, 2012. China said that it had detained seven company executives after tons of industrial waste including a toxic metal polluted a river, threatening water supplies for millions of people.
Polluted water pours from an abandoned communist-era gold mine near Rosia Montana village, Romania, on September 20, 2011. A Canadian group is planning an open pit mine that has divided people and created controversy throughout Romania. Romanian President Traian Basescu has expressed strong support for the project that will use large amounts of cyanide in an area famous for its Roman ruins.
(Daniel Mihailescu/AFP/Getty Images)
Figures in an underwater sculpture park between Cancun and Isla Mujeres, photographed on December 11, 2010. The sculptures created by British artist Jason de Caires Taylor used "life casts" made from materials that encourage coral growth to build an underwater installation on the sea bed off the coast of Cancun Mexico.