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Climate Change

Science Supporting Policy in California and Beyond

Photo: California's Sacramenot-San Joaquin Delta

The Sacramento-San Joaquin Delta is threatened by an anticipated rise in sea level as the climate warms.

Water Resources

How will proposed solutions for climate-induced sea level rise, increases in flooding frequency and increases in water temperature affect the Sacramento-San Joaquin Delta?

Jay Lund, Center for Watershed Sciences, has coauthored several key policy papers on resource management in the Delta as part of the Center’s Delta Solutions Program. Papers coauthored with the Public Policy Institute of California include Envisioning Futures for the Sacramento-San Joaquin Delta (2007), Comparing Futures for the Sacramento-San Joaquin Delta (2008), and Adapting California’s Water Management to Climate Change (2008). These publications describe scenarios and proposed solutions to managing the Delta resources under the threat of sea level rise, increased flooding frequency, and rising temperatures in streams and reservoirs. Lund and nine UC Davis authors published a comprehensive report Talking about the Weather: Climate Warming and California's Water Future (2003) for the California Energy Commission. This report combined models of urbanization and climate change with models for water availability in the year 2100. It built on an earlier report published in 2001 that estimated climate changes for 2020.

Has climate change been observed at Lake Tahoe and how does it affect the clarity of the lake and the local ecology?

Geoff Schladow, director, Tahoe Environmental Research Center, and his collaborators have determined that climate change is as important at Lake Tahoe as it is elsewhere in the Sierra Nevada. The hundred year data record from Tahoe City, California shows that minimum air temperatures have risen over four degrees Celsius and are now above the freezing point of water, the result of which is less snow, more rain, increased runoff and more erosion. There has also been a measured increase in the temperature of the lake over the last 40 years. The warming of the lake is double the rate of warming of the surface of the world's oceans. Lake Tahoe's clarity is largely affected by very fine particles that come from the air or enter the lake with the runoff from streams and urban areas. As precipitation patterns continue to change in response to climate change -- for example more rain and less snow -- and as the runoff changes with earlier snowmelt, the quantity and size of fine particles will change. Current research uses models to predict the magnitude of changes in clarity due to climate change. Rises in lake temperature have profound impacts on the lake ecology. Current research is looking at the impacts of climate change on algal species composition, invasive fish and aquatic weed populations, and the food web.

How will California's native fish population respond to climate changes?

Peter Moyle; wildlife, fish and conservation biology; researches the ecology and conservation of California fishes, in relation to change of all types—including climate change. His research program involves developing strategies for floodplain fish conservation in the Central Valley. He also developed methods to determine the health of mountain meadows by inventorying communities of plants, fish, aquatic invertebrates, and amphibians. He is reviewing the status of all distinctive types of salmonid fishes in California, and he conducted long-term studies of fish in Sierra Nevada streams, Putah Creek, and in Suisun Marsh. He served on the Ecosystem Restoration Program Science Board of the California Bay-Delta Authority and National Research Council Panel on the Klamath River. Moyle coauthored “Envisioning Futures for the Sacramento-San Joaquin Delta – 2007,” a report that presents the solutions to maintaining Delta as a productive, fish-friendly ecosystem.

How will climate change affect water resources in the arid western U.S., and how can these effects be managed or mitigated?

Graham Fogg; land, air and water resources; studies groundwater hydrology (hydrogeology) and alpine hydrology. He is interested in the effects of climate change on groundwater quantity and quality both in major water storage systems and in alpine systems (e.g., Tahoe Basin) under reduced snowpacks. Important questions include whether increased rain and less snow in California will increase groundwater storage in the central and coastal valleys, and whether the vast underground storage space can be used to offset the loss of surface reservoir space. His research on aquifer systems looks promising as a means of recharging groundwater during periods of high rainfall and runoff. His work on long-term sustainability of groundwater quality is critical for assessing water quality from underground water storage projects. Fogg also conducts research for optimally and safely injecting carbon dioxide into the deep subsurface of earth in carbon dioxide sequestration projects that can potentially isolate significant volumes of carbon dioxide at local power plants. Current work on groundwater storage in the Sierra Nevada Mountain range will provide better predictions of changes in both mountain ecosystems and runoff into the Central Valley during future climate change.

How will changes in sea level affect salinity intrusions into Californian estuaries?

John Largier, Bodega Marine Lab, environmental science and policy, and his research group are concerned about coastal flooding as sea levels rise, but they are equally concerned about a less visible issue. As the sea level rises, salty seawater will intrude up estuaries and into the lower portions of rivers and into groundwater aquifers. In flat lands, a foot increase in sea level may result in salinity intruding miles up-river during dry periods. Furthermore, with simultaneous changes in river flow in climates with reduced precipitation and more water extracted from upstream reservoirs, and in ocean winds and waves, seawater may intrude even further – changing critical habitats and threatening freshwater supplies to coastal towns and farms.

How will California's native fish population be impacted by climate changes?

Greg Pasternack; land, air, and water resources; constructed a new model for predicting the number of days each year that the flow of a river prepares it for Pacific salmonids to spawn. The model also predicts the subsequent number of days that river flow supports spawning and embryo incubation. Environmental resource managers may use this model to compare different rivers for their restoration potential as well as the impact of climate change on the native anadromous fish population of each river.