State water officials at the California Department of Water Resources (DWR) say they are cautiously optimistic that recent storms could replenish some of the state's heavily depleted water reservoirs. But after four years of drought, heavy rains of this frequency and magnitude also pose a threat to property, natural resources and human life.
Under Gov. Gavin Newsom's latest water supply strategy released in August, a myriad California agencies are bracing for the state's precipitation to swing more severely between drought and flood in the near future as the Western region of the country experiences a rapidly changing climate.
On the one hand, extreme rain is boosting California's snowpack. On Tuesday, DWR's snow survey team determined that parts of the Sierra Nevada have snow depths 177% of average for this time of year. But the same storms are bringing flooding to other parts of the state, said Karla Nemeth, director of DWR.
"This is a prime example of the threat of extreme flooding during a prolonged drought as California experiences more swings between wet and dry periods brought on by our changing climate," Nemeth said.
Michael Anderson, state climatologist for DWR, said that when looking at the bigger atmospheric patterns, the region will likely be in a transition period from the winter's fading La Nina conditions to neutral conditions within the next few months, lending an increased probability of extreme weather.
"It's sad to see with those higher (atmospheric river) scales, more hazards are introduced as the events become more extreme," Anderson said. "But there's a lot to storms beyond just the rain."
Drought Manager of DWR Jeanine Jones said that the state needs above-average precipitation throughout the rest of its wet season to reach 100% of average runoff.
"We are overcoming a deficit in soil moisture," Jones said. "We lose runoff until things get very wet, and we start getting good inflows into reservoirs and groundwater basins. But we do have deficit conditions in these basins from our prior dry years."
Deputy Director of Flood Management and Dam Safety for DWR, Gary Lippner, said that the state-federal Flood Operations Center is closely monitoring weather conditions to inform local partner agencies about elevated river and creek levels. He added that it's a multi-agency partnership across the federal and state level to minimize downstream flooding and provide resources to overwhelmed local agencies.
Lippner said Tuesday that the state's 1,600-miles worth of flood mitigation levees and weirs had enough capacity to handle the anticipated showers this week.
"That flood system is designed to take pressure off the mainstream rivers of the San Joaquin and the Sacramento river," said Lippner. "There is a fair amount of capacity in the system, certainly enough to handle the anticipated, forecasted flows for this week."
