California hasn't built a major reservoir in decades, and its most important reservoir by far -- the Sierra Nevada snowpack -- is in danger of shrinking because of global warming. Water agencies say those facts, coupled with projected population increases, mean that it is time for the state to get serious about building new dams. "Failure to consider these potential changes and develop the storage to address it will all but guarantee a future that swings from extreme floods to droughts on a regular basis," the Association of California Water Agencies reported in a "blueprint" for statewide water planning in...