Chennai, Aug. 6 -- Dozens of billion-dollar companies. Thousands of high-paying IT and manufacturing jobs. Luxury apartments towering over the Bay of Bengal. The southern Indian city of Chennai has one of the world's fastest-growing economies, but it's out of water, threatening to put a brake on all that growth.

In Chennai, a coastal city of about 10 million and the capital of Tamil Nadu state, rapid development and rampant construction have overtaxed a once-abundant natural water supply, forcing the government to spend huge sums to desalinate sea water, bring water by train from hundreds of kilometers (miles) away and deploy an army of water trucks to people whose household taps have suddenly run dry.

The water shortfall is disrupting ...