FOLSOM, Calif. (AP) — An unprecedented series of powerful storms has replenished most of California’s reservoirs, dumping record amounts of rain and snow and busting a severe three-year drought.

Some reservoirs are so full that water is being released to make room for storm runoff and snowmelt that could cause flooding this spring and summer, a new challenge for water managers and emergency responders. Twelve of California’s 17 major reservoirs are now above their historical averages following three years of drought that drained them to dangerously low levels.

It’s a stunning turnaround of water availability in the nation’s most populous state. Late last year nearly all of California was in drought.