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In the late 1980s, a Japanese scientist named Koji Minoura stumbled on a medieval poem that described a tsunami so large it had swept away a castle and killed a thousand people. Intrigued, Minoura and his team began looking for paleontological evidence of the tsunami beneath rice paddies, and discovered not one but three massive, earthquake-triggered waves that had wracked the Sendai coast over the past three thousand years. In a 2001 paper, Minoura concluded that the possibility of another tsunami was significant.

The drought-busting snow and rain in the mountains around Lake Tahoe have pushed the lake to its highest level in more than a decade. After five years of drought, the alpine lake atop the Sierra Nevada now has enough water to fill downstream reservoirs and meet the Reno area’s needs for at least two years, hydrologists say. “We are basically going from one extreme to the other in two years,” said Bill Hauck, senior hydrologist for the Truckee Meadows Water Authority.

After flows down Oroville Dam’s fractured main spillway were dialed back to nothing Monday afternoon, heavy equipment operators worked through the night to clear the massive debris pile that has formed at the base of the damaged concrete structure. The efforts to open the channel below the spillway, which will allow engineers to once again fire up the dam’s hydroelectric plant, appear to be paying off, said Nancy Vogel, a spokeswoman for the California Natural Resources Agency.

The extraordinary turnaround in California’s water picture is becoming a windfall for farm country. Federal officials announced Tuesday that the 20 reservoirs that make up the Central Valley Project are so swollen with winter runoff that many growers will get all the water they requested this year — a remarkable change from the past few years when countless orchards and fields received no federal water at all.