By Jay Lund
“Mega-drought” has become a frightful “thing” in public and media discussions. In the past 1,200 years, California had two droughts lasting 120-200 years, “megadroughts” by any standard. Could the state’s water resources continue to supply enough water to drink, grow crops and provide habitat for fish with such an extreme, prolonged drought today?
Clearly, some ecosystems and rural communities would be devastated by such a drought, and it would certainly affect all California residents. But with careful management, California’s economy in many ways could substantially withstand such a severe drought.
The UC Davis Center for Watershed Sciences explored this question a few years ago using computer models. We constructed a drought similar in scale to the two extreme ones found in California’s geological and biological records of the past 1,200 years (Harou, et al. 2010). We created a virtual 72-year-long drought with streamflow at 50 percent of current average rates, with all years being dry, as seen in the paleo-drought record.
We then explored the simulated drought using a computer model of California water management that suggests ways to minimize the economic costs of water scarcity for populations and land use in the year 2020.
Not surprisingly, the model results showed that such an extreme drought would severely burden the agriculture industry and fish and wildlife, and be catastrophic to some ecosystems and rural towns. The greatest impacts would be felt in the Central Valley.
However, if well managed, such a mega-drought would cause surprisingly little damage to California’s economy overall, with a statewide cost of only a few billion dollars a year out of a $2+ trillion-a-year economy.
The key to surviving such a drought lies in adaptive strategies such as water trading and other forms of water reallocation. These strategies would be essential to improving the flexibility of California’s water supply and demand system during such a prolonged drought.
Interestingly, most reservoirs we have today would never (yes, NEVER) fill during a decades-long drought. So expanding surface storage capacity for managing megadroughts would be futile.
California has a very flexible water supply system that can support a large population and economy under extreme adverse circumstances — provided it is well managed.
In adapting to the climate warming and changes that are upon us, the most important thing for California is to be well-organized and led for effective water management. Panic or complacency generally lead to poor decision. Good management of such a complex system will require serious and reasoned analysis and discussions, plus a political will to make reasoned decisions, even when ideal solutions do not exist.
Jay Lund is a professor of civil and environmental engineering and co-director of the Center for Watershed Sciences at UC Davis.
This article originally ran April 12, 2011. Some text has been updated,
Further reading
Harou, J. J., J. Medellín‐Azuara, T. Zhu, S. K. Tanaka, J. R. Lund, S. Stine, M. A. Olivares, and M. W. Jenkins (2010), Economic consequences of optimized water management for a prolonged, severe drought in California, Water Resources Research, 46, W05522, doi:10.1029/2008WR007681.
MacDonald, G.M. (2007), Severe and sustained drought in southern California and the West: Present conditions and insights from the past on causes and impacts, Quaternary International, 173-174: 87-100.
Stine, S. (1994), Extreme and persistent drought in California and Patagonia during medieval time, Nature, 369, 546–549, doi:10.1038/369546a0.
California cannot manage what it does not have. Droughts are caused by deficient precipitation, and megadroughts are caused by deficient precipitation for 20 years or more. However, precipitation is not the only source of water. The Pacific Ocean contains more than half of all water on Earth and can supplement California’s water supply, including filling surface reservoirs and groundwater basins, with desalination.
Thanks for distributing this article again- the finding about reservoirs not ever being full is a huge finding for public policy that has not seemed to be widely discussed.
On another note, did you look at use of RO to increase supply for those users near the ocean or estuaries?
YES, CA can!! — We need to STOP water releases for Electricity #1 and we need to RESTRICT Salt Water IMPORTS to the ports of Sac. & Stockton by adding tidally controlled louvers and automated gates for boat traffic.
The McDonald at the bottom under “further reading” is a broken link.
Thanks. This link should be fixed now.
I gather the operative thinking is “concrete good” , “natural processes bad.” Otherwise something would show up about the ability of beaver dams and beaver dam analogues to improve the water table and mitigate flooding while providing natural fire breaks.
Thank you for this. Suspect as long as politic is involved, logic, fairness will not be factors.
I appreciate your optimism and to realize there is quite a bit of flexibility in our current water delivery systems, which allow for scenario of continued economic stability and “support” for the human population. However, studying previous mega droughts does not account for the current crisis of groundwater depletion and the ecosystem being already in deep stress – before the next mega drought really hits it. It is a scenario we can’t really comprehend.
Question: What caused the “climate warming and changes” during the past 1,200 years?
Is the public getting accurate information about the crisis? One example: State officials claim Lake Shasta is at 25% capacity right now while photographs show it is much more depleted. Is this to prevent the panic that might lead to poor decision making? It concerns me that this is not getting the attention it needs.