Faced with water shortages, growing populations and the threat that climate change could make matters worse, governments around the globe have increasingly turned to cloud seeding in an attempt to wring more rain and snow from the sky. But the efforts are threatened by budget cuts in states struggling to begin an economic recovery and by critics who insist the technique is unproven and might pose a threat to the environment. In the U.S., utilities that run hydroelectric dams are among the most active cloud seeders. They say it is a cost-effective way to increase limited water supplies by 10 percent or more. Cloud seeding is also used in Texas and the Midwest to make hail smaller, reducing crop damage.