Lake Oroville contains about 3.2 million acre feet of water, making it the second-largest reservoir in California. It provides water for more than 22 million people and 700,000 acres of farmland. The lakenearly ruptured this week, swollen by a constant deluge of rain that overwhelmed the spillways and threatened to flood everything downstream. Keeping California properly hydrated requires some of the most complicated plumbing in the world.