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Scientists Forecast Water Shortages for One Billion Urban Inhabitants

A study recently published in the Proceedings of the National Academy of Sciences predicts that urban migration, coupled with the effects of climate change, will create water shortages for 1 billion people by 2050. Residents of Peru – South America's least water-secure nation – are already feeling the pinch of these combined factors. But the authors of the study assert that this crisis can be averted through sensible resource management and greater efficiencies, and political leaders in Peru are taking the challenge head-on.

A group of scientists from The Nature Conservancy, City University of New York, and Stony Brook University identified global climate change and the influx of 3 billion urban dwellers as the primary precipitators of perennial water shortages for 1 billion city residents in 2050. The authors define urban water shortage as "less than 100 [liters] per person per day of sustainable surface and groundwater flow within their urban extent." They also warn that freshwater ecosystems near these cities "will likely experience flows insufficient to maintain ecological processes."

The study, titled "Urban growth, climate change, and freshwater availability," modeled water availability for cities with a population greater than 100,000 in developing countries. The authors noted these cities had 1.2 billion residents in 2000, with demographic projections predicting they "will account for 74% of all urban growth globally from 2005 to 2050." The study makes clear that while "perennial water shortage is generally confined to cities in the Middle East and North Africa," continued urban population growth will create challenges for cities across the world.

Residents of Lima, Peru are already suffering from water shortages aggravated by climate change. The Independent (UK) recently profiled Lima as a "desert city in serious danger of running dry." Because of its unusual topography and the fact that the Peruvian population is concentrated on its western coast (two-thirds of the country's 30 million inhabitants live west of the Andes, while 98 percent of Andes run-off flows eastward to the Amazon basin) make Peru South America's most water-stressed nation.

Decreasing rainfall in the Andes threatens Lima's water supply. (Image credit: Wikimedia Commons user Dozenist)

According to The Independent, 1.2 million residents in Lima – of a total population of 8.4 million – live without running water and are forced to rely on inefficient, unreliable, and unregulated private water trucks that charge 20 times the cost of public tapwater. Moreover, the city's water infrastructure has a dismal 39 percent leakage rate. This situation is further pressured by the fact that climate change has dramatically reduced Andean rainfall and glacial ice – the only sources of water for Lima. The flow of the Rímac, the largest river that feeds the city, has declined 20 percent in recent years, now flowing at a meager 20 cubic meters (5,300 gallons) per second. Quelccaya, located in Southern Peru, remains the world's largest tropical glacier, but it is retreating by 60 meters (197 ft) annually.

Yet the authors of the study express optimism that major urban water shortages can be avoided, asserting their results should inform the decisions of planners and policymakers. In a statement to the Agence-France Presse (AFP), Rob McDonald, the study's lead author, asserted that the results serve as "a sign of challenge…There are solutions to getting those billion people water. It's just a sign that a lot more investment is going to be needed, either in infrastructure or in water use efficiency."

The study proposes two options for cities: infrastructure developments – dams, long-distance transport, aquifer tapping, and desalination – or better resource management. The authors emphasize that improved management techniques, greater efficiencies in agricultural, industrial, and residential sectors, and changes in land use patterns will provide more sustainable and durable solutions than costly and ecologically disruptive infrastructure.

An informal settlement outside of Lima, Peru. According to the Latin American Green City Index, only 87% of the city's residents have access to potable water.

In Lima, it seems that organizations and political leaders have recognized the dire consequences facing the city. The Latin American Green City Index, published by Siemens last year, reported that the city has progressive water policies aimed at "reducing water stress, consuming water more efficiently, and also actively promot[ing] public awareness about efficient water consumption." Recently-elected mayor Susana Villarán has admirably pledged to "bring running water and sewerage to all Lima households by 2014." The Nature Conservancy, Grupo GEA, and the Fondo de las Américas (FONDAM) recently launched Aquafondo, the Lima Water Fund to "finance conservation projects such as stabilizing slopes, recovering lagoons, and reforestation in the watersheds."

While water shortages are a global challenge, every individual can make a positive impact: the average U.S. citizen uses an embarrassing 575 liters (152 gallons) of water every day, compared to the average Peruvian's 170 liters (45 gallons).