So much rain has fallen in Northern California recently that federal officials have done what would have been unthinkable a year ago. They opened the spill gates at Folsom Lake and let precious water tumble into the American River as a precaution against — of all things — flooding.

A series of storms during this “Miracle March” has caused Folsom and two of its neighbors, Lake Oroville and Shasta Lake, to swell. The massive reservoirs are at above-average levels for the first time since the spring of 2013.