Wildfire pours ash onto San Francisco reservoir

A raging wildfire in Yosemite National Park has rained ash on the reservoir that is the chief source of San Francisco’s famously pure drinking water.

Utility bosses scrambled to send more water towards the metropolitan area before it became tainted as nearly 3,700 firefighters battled the 230-square-mile blaze, the biggest wildfire on record in California’s Sierra Nevada.