There are several ticking time bombs in western water. The first is obvious. How much less water will fall from the sky because of climate change? Another big one is barely talked about and will take decades if not a century to end. How will bureaucrats, lawmakers and the courts deal with the rights of Native American tribes that have claims to water from the Colorado River? The Colorado is already suffering because states that rely on it — largely California and Arizona — are taking more out of the river than snow and rain put back in. After two decades of drought, this “structural deficit” is close to becoming a crisis for millions of Americans and Mexicans who depend on the river’s water.