1.21 billion people, primarily depend on surface water sources

1.21 billion people, primarily depend on surface water sources

ARLINGTON, VA, June 5, 2014 — According to recent statistics, a number of cities throughout the globe are experiencing increased water stress and looking for additional water supplies to support their continued growth, as more people move to urban areas.

Source: Waterworld.com
The first global database of urban water sources and stress, published in Global Environmental Change on Tuesday, June 3, estimates that cities move 504 billion liters of water — enough to fill 200,000 Olympic swimming pools — a distance of 27,000 kilometers every day. While large cities only occupy 1 percent of the Earth’s land surface, theirsource watersheds cover 41 percent of that surface, so the raw water quality of large cities depends on the land-use in this much larger area.
  • Four in five (78 percent) urbanites in large cities, some 1.21 billion people, primarily depend on surface water sources. The remainder depend on groundwater (20 percent) or, rarely, desalination (2 percent).
  • The urban water infrastructure of large cities cumulatively supplies 668 billion liters daily. Of this, 504 billion liters daily comes from surface sources, and that water is conveyed over a total distance of 27,000 km.
Accordingly, a team of scientists working at the Socio-environmental Synthesis Center, led by Rob McDonald, senior scientist with the Nature Conservancy, surveyed and mapped the water sources of more than 500 cities globally, providing the first global look at the water infrastructure that serves the worlds large cities.
They used computer models to estimate the water use based on population and types of industry for each city and defined water-stressed cities as those using at least 40 percent of the water they have available. Previous estimates of urban water stress were based only on the watershed in which each city was located, but many cities draw heavily on watersheds well beyond their boundaries. In fact, the 20 largest inter-basin transfers in 2010 totaled over 42 billion liters of water per day — enough to fill 16,800 Olympic size pools.
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