Sunday’s storms brought more rain to Northern California, but they also helped the state hit a key milestone in its efforts to recover from the historic four-year drought.

Shasta Lake, the largest reservoir in California and a critical source of water for Central Valley farms and cities from the Bay Area to Bakersfield, reached 100 percent of its historic average Sunday as billions of gallons continued to pour in from drenching downpours. The 21-mile-long reservoir, north of Redding, holds enough water when full for the needs of 23 million people for a year.