Water is becoming so precious in the drought-stricken U.S. West that -- why not -- states are even taking steps to figure out how much of it they have.
California governor Jerry Brown in January challenged towns and state agencies to cut their water use by 20 percent. Now they're trying to measure what 20 percent means. It's hard. Cities and the state in some cases are coming up with estimates that differ by up to 10 times.