Extreme drought, severe flooding and the recent near-disaster at the Oroville Dam have all taken a toll on California’s aging water infrastructure.
As climate change presents new challenges, scientists and environmental groups are proposing augmenting California’s “gray” infrastructure of concrete dams, aqueducts and other structures with floodplains and other “green” infrastructure, including better-managed watershed forests and restored wetlands.
Gray infrastructure includes human-engineered solutions that often involve concrete and steel. Green infrastructure is an approach to water management that protects, restores or mimics the natural water cycle.
“It’s kind of an all-of-the-above strategy for securing California’s water future,” said Jeffrey Viers, an associate professor at the University of California, Merced.
Viers is the principal investigator on several studies on the Cosumnes River, which he referred to as the state’s “ugly duckling” since it is the only major river on the western slope of the Sierra Nevada that doesn’t have a dam. As a result, flooding is largely uncontrolled.
“It’s proven to be a great system that allows us to study the benefits of floodwaters for ecosystems,” he said.
Viers and other scientists contend that by moving some of California’s 13,000 miles of levees back from rivers to make floodplains, excess flow from rivers would be absorbed without endangering cities built along rivers. In addition, the floodwaters would recharge groundwater stores and provide vital aquatic habitats for endangered species.
When drought conditions return, the surplus groundwater can be pumped out to serve farms and neighborhoods. Since about 40 percent of California’s water supply comes from groundwater, Viers said, even small floods can make an impact.
The flaws in California’s water infrastructure were brought to light by the threat of catastrophic flooding from the damaged Oroville Dam in Northern California in February, forcing the evacuation of nearly 200,000 people.
The culprit at Oroville was a faulty emergency spillway, used for the first time since the dam was opened in 1968 after days of drenching storms.
Engineers and environmentalists believe that similar problems could occur at many of the roughly 1,400 dams in the state, many of which are suffering from age and stress.
“Oroville wasn’t designed in a way to withstand floodwaters without serious work,” said Brian Stranko, director of the state water program for The Nature Conservancy. “We need our infrastructure to deal with more challenging weather events than we have in the past.”
In 1999, the conservancy bought the McCormack-Williamson Tract in the Sacramento/San Joaquin Delta. Formerly an island of low-lying farmland, it is currently a 15-foot-deep lake that was created by intense storms that caused a levee to break. The Nature Conservancy plans to re-engineer the levee system to convert the tract into a permanent floodplain.
While gray infrastructures like dams have their place in water management, Stranko said, they were not designed to handle the heavy precipitation that California has been receiving in recent months.
“We need to be able to use green infrastructure in strategic ways,” he said. “If we combine the green with the gray, we can have nature do a substantial part of flood protection.”
Climate change increases flood hazards, according to experts. A study published in February 2016 in Geophysical Research Letters states that atmospheric rivers — narrow corridors or filaments of concentrated moisture in the atmosphere — have been causing drenching storms on the West Coast that are leading to floods and landslides.
Days on which atmospheric rivers reach the West Coast each year could increase by a third this century if greenhouse gas pollution continues to rise sharply, the authors wrote.
Jeffrey Mount, a senior fellow with the Public Policy Institute of California, wrote in a recent blog post that California’s dams were built to respond to early- to mid-20th century conditions and cannot meet the demands brought about by climate change.
“Our dry periods are getting both drier and warmer, and our wet periods are getting wetter with more precipitation falling as rain rather than snow,” Mount wrote.
According to Graham Fogg, a professor of hydrogeology in the Department of Land, Air and Water Resources at University of California Davis, global warming has caused less water to stay in California’s snowpack. As a result, there is more runoff in winter and spring, which ends up in reservoirs and dams.
Consequently, those structures are less equipped to accommodate heavy precipitation, and the risk of flooding and dam failures heightens.
“If you’re looking for more space to store water, by far the most space is underground,” Fogg said.