Yesterday’s Dams Face Tomorrow’s Floods
The crisis at Oroville Dam on the Feather River eased yesterday as state officials gained control over the damaged spillway and allowed the more than 180,000 evacuees to return home. Prospects are good that dam operators will be able to control releases through the remainder of the wet season. Now that the immediate crisis is past, we should take the opportunity to review how we manage California’s big dams—and what changes would help us do so more effectively in future.
Water—whether too much or too little—has a way of revealing weaknesses in design and decision making. For Oroville Dam—the tallest dam in the nation—the crisis began with poor maintenance of its main spillway compounded by wholly inadequate design of the emergency spillway, a known problem. But the crisis at Oroville also raise five broader concerns that California will have to reckon with:
- Aging dams. Most of the state’s 1,400 large dams were designed using slide rules and based on simplistic assumptions about hydrology and earthquakes. These dams are marvels of engineering considering when they were built, but many are in need of major upgrades in infrastructure and operations. California needs a comprehensive plan for evaluating and modernizing these structures.
- A changing climate. California’s dams must be adapted to address new risks from a changing climate. These dams were built to respond to early- to mid-20th century conditions. The climate has shifted since that time, and the bulk of climate simulations point to significant changes in the near future. 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. Part of the problem at Oroville is that the warm temperatures have meant there’s more water to manage right now than usual because less of it is staying in the snowpack. The past seven years—which included five years of record warm, dry conditions bracketed by extremely wet ones—is a glimpse into our future. It is time to rethink how we are going to operate and maintain our dams to respond to these changes.
- Conflicting goals. We may be asking too much of our dams. For example, Oroville Dam provides water supply, hydropower, flood management, recreation, and ecosystem flows for rivers and the Delta. Flood management is in tension with the other services because a mostly empty reservoir—bad for the other services—is the best hedge against floods. By design, Oroville was relatively full when the latest floods arrived, reflecting its top priority (water supply) and compounding flood risk. It may be time to rethink the balance of objectives for all of our large, multipurpose dams.
- Rigid rules. Adjusting course on dams—whether by changing the infrastructure or the way they are operated—is difficult. Licenses for non-federal dams like Oroville—administered by the Federal Energy Regulatory Commission—last for 30–50 years. These lock in place all aspects of dam operation for several generations and require herculean efforts to overcome. Moreover, flood operations on all dams are mandated by the US Army Corps of Engineers and require an act of Congress to change. When it comes to changing course on dams, institutional inertia is a powerful countervailing force.
- High cost of improvements. Any change in course is likely to be very expensive. California relied heavily on federal support for construction of many of its large, multipurpose dams. Support ended decades ago and is unlikely to resume in the future. California is going to need a comprehensive funding plan for modernizing its dams and other flood management systems that does not rely on extensive federal support.
Most water crises have a silver lining. The recent drought spurred changes to the way we manage water scarcity in the state, resulting in one of the most important pieces of water legislation—the Sustainable Groundwater Management Act—in many decades. The crisis at Oroville should spur Californians to rethink how we manage our network of large dams. New management approaches, new technology, and new investments to modernize dams will be necessary to adapt to changing conditions, both today and tomorrow.