Development and daily activities, such as watering a lawn, are putting stress on the world's water supply, Alexandra Marks writes. In 1990, 30 U.S. states had problems with water shortages, but the number increased to 45 in 2009, according to the Web site Earth Easy. To combat the problem, new homes are expected to have water-efficient landscaping, and a certification program called WaterSense could help reduce water usage in homes by an average of more than 10,000 gallons per year.

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