After construction concluded on the Oroville Dam in 1968, Lake Oroville became the second largest reservoir in California and the tallest dam in the United States—40 feet taller that the Hoover Dam. It holds 3.5 million acre-feet in water storage and mandatorily exports and supplies water to the Sacramento and San Joaquin delta, along with surrounding rural areas of Sacramento Valley.
However, despite nearly four times the amount of rainfall throughout the North State in November and October, water in Lake Oroville is still below average storage levels due to demands downstream.
“In general, the lake level is lower than average for this time of year,” said Kevin Dossey, senior civil engineer of the California Department of Water Resources. “It’s about three-quarters lower than it usually is.”
Because the ground surrounding Lake Oroville remains dry from recent drought conditions, rainfall only has significant impact after long durations of downpour.
“Well, the fact that we got four times the amount of participation in October was a little glimmer of hope, but I don’t think officials are ready to call the drought over,” Dossey said. “Groundwater basins are still depleted. It will take heavy, heavy rainfall in a precipitating year.”
The historical average shows the reservoir capacity is at its lowest point during the months of November and December. During the summer months, levels typically rise due to spring rainfall and snowmelt from the Sierra Nevadas and surrounding mountains.
“What we really want is to have the snowpack build up,” Dossey said. “Last year had really high snow levels. The positive to that is that water just runs off into the lake. It’s definitely the main contributor to the storage in the lake.”
Even in years without drought conditions, Lake Oroville levels raise concerns with local farmers and water critics. After last year’s “El Nino” winter, for the first time in five years, the Oroville Dam spillway was opened.
The spring to release water for “emergency flood conditions” and demands from The main sources that draw and mandate the water from lake are agencies like the U.S. Fish and Wildlife Foundation and National Marine Fisheries Services.
“Despite our first wet winter in years, misguided federal agencies threaten to cut off the water supplies of millions of Californians,” Congressman Doug LaMalfa said in a recent press release. “Neither demand is backed by science, and the only common theme is that both give Californians the short end of the stick.”
A few months later more water was exported due to demands from the Army Corps of Engineers and the State Water Resources Control Board located in Sacramento.
“The demand does fluctuate throughout the year,” said Eric See, environmental program manager of the DWR. "The environmental conditions make a big factor on when they can move water. When fish are migrating through the delta, it might being pumping down or shut it off completely.”
The different departments are diligent and consistent when it comes to exporting water throughout the year. For the last 30 years Lake Oroville has seen much of the same rising and lowing in levels.
“The water was rising for about a week or so but it started dropping again last week. The rain runoff has seized and slowed down to the point where we’re exporting or releasing more water than is coming in,” Dossey said.
Local water distribution has been a controversial subject surrounding the Oroville Dam for years. However, water still gets rightfully distributed to rice farmers the central valley have owned “senior” water rights before the California Department of Water Resources.
These regulations were set in motion long before controversy was a normal discussion surrounding Northern California water.
“It’s very controversial. There’s a constant back in forth,” See said. “Much of the water in Lake Oroville is used local water delivery, local irrigation. Not for the San Joaqin Valley or Southern California."
-- Matt Manfredi