It may seem counter-intuitive, but Las Vegas, on the edge of the Mojave Desert, is not in immediate danger of going dry. The city draws a massive amount of water from the Colorado River by way of the Hoover Dam, and recent improvement to the pumping facilities at Lake Meade have provided a fail-safe mechanism.

Unaddressed failing infrastructure, drought, water waste, lack of surface water resources (rivers, lakes, snow run-off), poor planing, aquifer problems, population overload, and pollution are the major reasons these cities are in danger of having too little drinking water and facing a crisis.

The list, including the main reasons for water woes, follows:

1. Cape Town: prolonged drought

2. Sao Paulo, Brazil: prolonged drought, poor planning, no infrastructure investment

3. Bangalore, India: overpopulation, failing infrastructure, pollution, water waste

4. Beijing, China: minimal water resources, pollution

5. Cairo, Egypt: pollution

6. Jakarta, Indonesia: aquifer problems

7. Moscow, Russia: pollution

8. Istanbul, Turkey: overpopulation, drought

9. Mexico City, Mexico: no water resources, overpopulation

10. London: infrastructure, water-waste

11. Tokyo, Japan: drought (plenty of rain, but only four months a year, so a disappointing rainy season means trouble)

12. Miami, Florida, USA: aquifer problems

More Info: www.bbc.com