In the years before California’s civil engineers got around to confining the Sacramento River, it often spilled over its banks, inundating huge swaths of the Central Valley.
This winter, for the first time in a decade, and after five years of a crippling statewide drought, the Yolo Bypass is submerged again.
In the past five months—the wettest since record-keeping began, in 1895—California has experienced widespread hydrological chaos.
In January, after a series of heavy rainstorms, water managers activated the Sacramento Weir, filling the Yolo Bypass.
Less than a year ago, Lake Oroville was a vivid symbol of the state’s prolonged drought.
But Peter Gleick, the chief scientist at the Oakland-based Pacific Institute, told me that one year of heavy precipitation, even a record-breaking one, will not undo the most serious repercussion of the drought: a severe deficit of groundwater.
These days, though, more precipitation falls as rain than as snow, placing stress on the reservoirs.
“Unless a massive effort is made to both reduce overdraft and to artificially enhance recharge rates, California’s groundwater will continue to decline,” he wrote in an e-mail.
Last Friday, the state’s Department of Water Resources reopened the patched-up concrete spillway at Lake Oroville.
At the moment, there is no large-scale engineering system that would allow the huge surge of surface water currently flowing across California to be delivered to the Central Valley’s aquifers.