National Geographic: Most of California's water comes from the snow stored in the Sierra Nevada each winter. In the spring, melting snow helps fill the state's reservoirs for the dry summer. (Read "When the Snows Fail" in National Geographic magazine.)
As the state's historic drought drags on, scientists are watching the Sierra snow with intense interest-and they're worrying that even tiny airborne particles of dust may have a big effect on water supplies.
Here's how: As California gets drier, it's getting dustier,...