A recent computer model study indicates that some California dams, including Pine Flat on the Kings River could be removed with small reductions in water supply and hydropower generation and considerable gains in habitat for Chinook salmon and other native fish.  Built in 1954, Pine Flat Dam impounds up to 1 million acre-feet of water. Source: Wikimedia Commons

By Sarah Null

In California, we ask water managers to do the near-impossible task of managing rivers for both environmental and economic objectives, which are often at odds. Where we have repeatedly failed to stem or reverse environmental problems, environmental regulation can drive water management.

California’s Bay Delta – a water source for 25 million people and about 3 million acres of farmland – is a prime example. No sooner did Gov. Jerry Brown declare a statewide drought emergency in January than enforcers of the Endangered Species Act ordered big cuts in Delta water exports to protect the delta smelt, a native species on the brink of extinction.

To better manage water for both people and ecosystems, we have a range of options:

• Keep doing what we’ve always done and expect different results
• Accept that aquatic and riparian restoration are ongoing costs of water management
• Weaken environmental laws and the resources they protect
• Directly address environmental problems

Addressing environmental problems directly would allow water supply, hydropower, flood control and other economic objectives to play a larger role in decision-making.

One way to fix environmental problems is by removing some dams, using a systems analysis to evaluate costs and benefits and prioritize for removal.

Typically, these studies are done site-by-site. They do not look at how the remaining system of dams could be re-operated to minimize water scarcity, maintain hydropower generation, maintain flood protection and improve environmental performance.

Also, most dam removal studies overestimate water supply benefit because they use reservoir storage capacity as the economic metric. Storage in watersheds has decreasing marginal economic benefit – the millionth acre-foot of storage is less valuable than the first acre-foot. Reservoir space to store water and water to fill that space are not the same.

These oversights potentially limit the pool of candidates for removal. Better methods are needed to prioritize dams that could be removed within larger water systems.

Red hues show watersheds having more water storage behind dams than the mean annual streamflow. Bluish watersheds have less storage than mean annual streamflow.  Source: Null et al. 2014

For regions like California with extensive interconnected water systems, we may be able to remove some dams without reducing overall economic benefits. The state certainly has no shortage of potential candidates for removal. Some dams would not be built today because their environmental or socio-economic costs exceed benefits. Other large dams were built subsequently to smaller dams, creating redundancy and excessive storage space in some watersheds.

Researchers with Utah State University’s Watershed Sciences Department and the Center for Watershed Sciences at UC Davis recently tested the potential for removing dams from inter-tied water systems.

We evaluated tradeoffs between fish habitat gains and water supply and hydropower losses from dam removal in California’s Central Valley. Using an economic-engineering water management optimization model known as CALVIN, we also assessed dam removal with the historical hydrology and with a warmer and drier hydrology expected with climate change.

The study indicated that demolishing some dams, such as Whiskeytown, Pine Flat, Pardee, Camanche and Englebright, would likely improve habitat for migratory fish and warrant additional study. Removing some dams, however, relies on keeping and maintaining other dams. The research indicates that Shasta and Oroville dams are foundational to maintaining California’s water supply.

Tradeoff between water deliveries and fish habitat with dams removed under climate change conditions. Points toward top left show dams (larger ones labeled) that could be removed with small reductions in water deliveries and considerable habitat gains for salmon and steelhead. Total statewide farm and urban deliveries are 45.6 billion cubic meters. Source: Null et al. 2014

The study also shed light on the changing benefit of dams through time. California will face increased water scarcity with the anticipated warmer and drier climate. Streamflows will be immediately delivered to urban and agricultural users, likely leaving several large reservoirs empty for much of the year – as we saw during the extremely dry months this past summer through winter.

All this suggests that the economics of removing dams may be increasingly feasible in the future.

Sarah Null is an assistant professor of watershed sciences at Utah State University and an alum of the Center for Watershed Sciences at UC Davis.

Further reading

Bernhardt, ES, and M Palmer. 2005. “Synthesizing U.S. River Restoration Efforts,” Science 308 (5722): 636-637

Hanemann, M, and C Dyckman. 2009. “The San Francisco Bay-Delta: A Failure of Decision-making Capacity.” Environmental Science & Policy 12 (6) (October): 710-725. doi:http://dx.doi.org/10.1016/j.envsci.2009.07.004

Kareiva, PM. 2012. “Dam Choices: Analyses for Multiple Needs,” Proceedings of the National Academy of Sciences 109 (15): 5553-5554

Null, S.E., J. Medellin-Azuara, A. Escriva-Bou, M. Lent, J.R. Lund. 2014. “Optimizing the Dammed: Water supply losses and fish habitat gains from dam removal in California.” Journal of Environmental Management. doi:10.1016/j.jenvman.2014.01.024

Excerpt of President Kennedy’s remarks at the Sept. 28, 1963 dedication of the Whiskeytown Dam and Reservoir.

Source: John F. Kennedy Presidential Library and Museum