A Soggy California Examines Its Flood-Control Performance
SAN FRANCISCO — The rains have stopped, but California's water woes are far from over.
The series of winter storms that flooded California's Central Valley have stretched the state's water-control system to near capacity. Though water levels are now dropping, experts warn that any new large downfall could trigger an even more dangerous overflow of water.
"We don't want to even think about another storm," says Dave Reynolds, a science officer for the National Weather Service regional headquarters in Monterey, Calif. "The ground is absolutely saturated and the reservoirs are full, so any rain that falls is going to run off immediately."
Still, California's elaborate system of dams, levees, bypasses, and channels has managed to withstand a flood that ranks among the two or three worst in state history. While water levels are higher than the devastating inundation of 1955, which also struck the farm lands of the Central Valley, the destruction and the loss of life have been less.
"To date, in many respects, the system has functioned very well indeed," says Pete Weiser, an official of the Department of Water Resources working in the state-federal Flood Operations Center in Sacramento. Mr. Weiser cites the timely discharges from huge reservoirs, the delivery of early warnings to residents to evacuate threatened areas, and improvements to levees in the Sacramento region since the last serious flood in 1986.
The storm system that hit northern California, Idaho, and northern Nevada over the past week is only the latest in a series of winter storms that dumped record levels of snow or rain on the entire Pacific Northwest since Christmas. The storms have resulted in at least 23 deaths and forced the evacuation of tens of thousands of people from their homes, including about 140,000 people in California. Residents began to return to mud-coated dwellings over the weekend.
On Saturday, President Clinton declared "a major disaster" in areas hit by the most recent storm, including 37 California counties. On Sunday and Monday, James Lee, director of the Federal Emergency Management Agency, toured the stricken communities.
Federal and state authorities are only beginning to gather information on the amount of damage caused by the latest storms. But California officials already believe this could be the most costly flood in state history, says a spokesman for the Office of Emergency Services.
These floods represent the most serious test so far of California's water-control system - and show that the state has taken to heart lessons learned from earlier floods.
The 1955 flood, which left 76 people dead, launched the state's effort to build what has become today's labyrinthine network. Another serious flood in 1986 prompted state and federal authorities to set up joint operations facilities, including a flood crisis center. Together state and federal agencies oversee two massive interconnected systems - the State Water Project and the Central Valley Project - that shift water from the north and the Sierra Nevada mountains to the agricultural lands of the valley and the thirsty cities of southern California.
But it is far too early to declare victory over the raging waters. "This game is a long way from over," says Weiser. "The rainy season has a long way to go."
In fact, the water-control system is already stressed close to its maximum carrying capacity in many areas, he admits. Lake Shasta, the reservoir behind the largest dam in the state, controlling the Sacramento River, is at 97 percent of its capacity. Oroville Dam on the Feather River and Folsom Dam on the American River are at more than 90 percent capacity. Smaller reservoirs in the hills above the San Francisco Bay Area are completely full, as are dams above the San Joaquin River.
The reservoirs are being filled not only by rainfall, but also by unusual melting of the Sierra snowpack. According to Mr. Reynolds of the National Weather Service, some four to eight feet of snow had accumulated just before the storms hit. The storms were formed by what meteorologists call "the pineapple connection," a shift of the jet stream to the south, carrying warm subtropical air into California. Instead of adding to the snow accumulation, the warm rain melted the snow.
Historically, California has been whipsawed by periods of drought, the latest lasting six years until 1992-1993, followed by wet spells. This is the third year of heavy rains.
"The problem we always have with water in California is that it is so valuable we can't stand to get rid of it," says Reynolds. "This rain exceeded all expectations."
Officials have had to release huge amounts of water to avoid dam breaks, a flow that has been responsible for some of the worst flooding.
The levee system has held up fairly well, authorities say, with only four breaks. But one of those sent flood waters into Olivehurst and prompted the evacuation of about 100,000 people in Yuba City, Marysville, and other nearby towns. Though skies have cleared, authorities are concerned about high winds expected to sweep across the valley and send waves crashing against the weakened levees.