Heavy rains and melting snow in California are increasing flooding concerns and stressing California’s water infrastructure. Two years ago, the Uvas Reservoir stood at 2% of its capacity; today it’s spilling over and sending water downstream, threatening to flood out the area’s lone bridge. On February 12, 2017, heavy rains forced the evacuation of almost 200,000 residents after a warning was issued about a possible impending collapse at the Oroville Dam. California’s largest reservoir, Lake Shasta, began releasing water through its spillway for the first time since 2011. Recent storms have also damaged California’s flood control system as well as transportation infrastructure.
The recent heavy rains exacerbate the threat that earthquakes pose to poorly maintained dams. For example, the Anderson Dam could inundate a city of 41,000 south of San Jose if a major earthquake hits it at capacity. As a result, regulators ordered it to be kept at 2/3 capacity until a $400 million seismic retrofit starts in 2020; unfortunately, Lake Anderson has filled faster than it can be safely drained as the local area has received twice the normal amount of rain.
Almost 300, or 35% of “high-hazard potential dams” in California do not have an emergency action plan, compared to 20% nationally, according to the 2016 National Inventory of Dams. California Governor Jerry Brown has ordered emergency action plans and flood inundation maps for all California dams. Governor Brown said that, though he intends to spend $450 million on flood control, almost $50 billion is still needed for a completely upgrade to the state’s flood management infrastructure. He has urged the federal government to conduct expedited reviews of high priority projects such as the Oroville Dam.
The state is never far from drought, and the limited storage capacity of California reservoirs means they are unable to recover spilled water after reservoirs reach capacity. New projects to expand water capacity have faced barriers. One example, the Centennial Dam, has been proposed along the Bear River in the Sierra Nevada region of California in order to help compensate for a dramatic decline in it’s traditional source of water, the Sierra snowpack. The district was forced to buy emergency supply water from the Rollins Reservoir in 2015, a resource that may not be available a second time as climate change continues to decrease the historically relied upon snowpack. Alternatively, the high environmental cost of dams, and the fact that 1,400 already exist, has pushed some to support the growth of underground storage as a solution to the state’s water problems.
For more information, see GRI’s recent post “Oroville Dam Erosion Forces Evacuation of Hundreds of Thousands of Residents.”
California’s Dams Set to Face New Stress Tests – Wall Street Journal