Mapping Sea Level Rise On The California Coast
Ξ March 12th, 2009 | → 0 Comments | ∇ Uncategorized |
The Pacific Institute has posted a report accompanied by a series of maps to illustrate the serious future ahead for California’s coast should nothing be done to curb green house gas emissions. The news caused quite a stir. I’ve been told the servers at the Pacific Institute nearly crashed from the traffic pouring in today. The report posited a moderate sea level rise of 1.4 meters and its impact on agriculture, civil infrastructure such as schools, hospitals, businesses and roads, and populations. Also extrapolated was the fate of wetlands and varied ecosystems. Much more is discussed. The report is required reading.
Pacific Institute’s effort is part of the ongoing research supported by the California Energy Commission’s Public Interest Energy Research (PIER) Program. For a good overview read the presentation on Aquafornia.
I contacted Pacific Institute for more specific information and was generously granted an interview with Dr. Juliet Christian-Smith, a specialist in agricultural water uses and climate change.
Admin Thank you speaking with me on such short notice. Can you tell us what it is you do at the Pacific Institute?
Dr. Juliet Christian-Smith I’m a Senior Research Associate at the Pacific Institute based in Oakland, California.
Can you explain the modeling that informs Pacific Institute’s report, The Impacts of Sea Level Rise On The California Coast?
Dr.JC-S The modeling is actually based on a series of reports and studies that were put together for the California Energy Commission’s PIER Network. It is all available on-line. Daniel Cayan played an important part. What they did was down-scale these large global climate change models to the California area. And they have a series of projections in terms of changes in temperature, precipitation, snow melt timing, sea level rise etc., out to 2050 and out to 2100.
They’re done for several different green house gas emission scenarios. So we used that data as a basis, and we used the medium-to-high GHG emission scenario, (but not the high or worst-case scenario) for our report. Generally it is difficult to tie together weather and climate change for people because weather is constantly changing, and global climate change occurs on a different scale. There is not a one to one ratio between the two.
I think what we’re already seeing in many parts of the world, for instance, the ten year drought in Australia, is an indicator of what they, the Australians, perceive to be a new climate, the embodiment of climate change on the ground there.
And the recent fires. I have read some models that estimate the end of wine grape growing in Australia by 2050.
Dr.JC-S Right. I was at a conference with the head of the Murray Darling Basin Authority last week, Senator Penny Wong. The Murray Darling Basin has alot of Australia’s agriculture. And she was speaking about their water allocation system, how much of the water that was at one point delivered to irrigators is no longer being delivered, or there is a share of the initial allocation being diverted or transferred to other uses. So there is a shift away from agriculture occurring in that Basin.
Now, about your maps which show in shocking detail predicted sea level rise. I was wondering about the effect on fresh water supplies well before the scenario depicted reaches either its 2050 or 2100 endpoint. Wouldn’t there be earlier episodes of saltwater intrusion into the water table, and reservoir and lake contamination?
Dr.JC-S Well, we’re already seeing it in the Pajaro Valley here on the Central Coast of California. Now, some of the saltwater intrusion is occurring because of overdraft of ground water basins. This is exacerbated by sea level rise. So where you have an area that is already taking more from the water table than can be sustained, lowering it below the sea level at the coastal edge, then you will have saltwater infiltration. As sea level rises this will increase the pressure, increase the concentration of saltwater coming in. So we’re beginning to see these problem already occurring in coastal areas of California.
What our report looked at was this trajectory without any changes in GHG emissions. We really hope the report will serve as an entry point for policy makers and interested, concerned citizens to say we have some information, now what can we do to protect our coastal areas? I guess for your readers the question is how to we protect our in-land, low-lying agricultural areas.
The maps from the Napa and Sonoma regions are showing a sea level rise affecting primarily low-lying pasture lands and ranch lands. We didn’t actually go into depth with respect to land use classification. But if you wanted to do that all of our GIS data layers are available on-line. You can download particular counties and overlay them on Dept. of Water Resources’ Irrigated Crop Area data to find where they intersect.
Let’s take the Russian River area around Guerneville and above where there’s quite alot of high-value vineyard land, we’ve only looked at inundation from sea level rise. We haven’t looked at the runoff changes coming from changed precipitation patterns and snowmelt. So there is going to be an interaction between the coastal inundation and the riverine flooding. That will change the dynamic of those floods in inland river systems.
It must be that vineyards at slightly higher elevations, just above inundation, would still be affected owing to the necessity that they draw water from the basin below.
Dr.JC-S Yes, particularly along the Russian River. There you have a great many wells that are tapping into sub-surface flow. If the river is becoming saltier down towards the Jenner mouth then you will have issues with those groundwater wells.
Just because your maps show inundation that is really not the full extent of the threat.
Dr.JC-S Exactly. That’s a very important point. Not only is not the full extent, not only is it not incorporating riverine flooding, changed runoff patterns and snowmelt, it is also the medium-to-high GHG emission scenario. It is not the high or worst-case emission scenario, nor is it incorporating the increased glacier melting we’re finding more about.
What about the importance of the so-called 100 year flood events?
Dr.JC-S Another interesting point. The 100 year flood equation, it’s called the Rentz equation, is not sensitive to increased variable events. I know that there are some hydrologists at Berkeley right now working on revising that equation to incorporate more stochastity, more variability in the timing of flows and high flows.
What do you say to those who suggest it is already too late to turn back the tide of GHGs? How quickly must we act to avoid the sea level rise scenario you’ve laid out?
Dr.JC-S The only answer is that we must take action now.
Let’s look at it another way. Caltrans, one of the funders of this project, is making plans about the future of our state’s infrastructure, highways, roadways… and those choices should be informed by our analysis and will be. Whether we’re siting new developments, new schools, hospitals, industries, we should have an idea of the risks that are involved. And we should use this information to protect vulnerable communities.
Could you say a little more about the challenges agriculture faces? Which crops?
Dr.JC-S This report is bringing to light the aspects of sea level rise that are critical to understand for our coastal and some inland areas. We also want to do studies looking at agricultural adaptations to climate change. So we have information based on the same series of studies by the California Energy Commission [see link above] that tell us we can expect higher temperatures and variable precipitation. That translates into changes in evapotranspiration. The question become how do we begin to adapt to unavoidable impact, and how to delay or mitigate those impacts that we still have time to stall.
Such a study would work with local irrigation districts, resource conservation districts, agricultural organizations to assess where climate change planning is right now in their communities. We want to provide a toolbox of approaches to help local communities think through their options, to promote specific adaptation strategies for their area.
And the question begs as to the kinds of crops California will continue to be able to provide. Avocados use alot of water. Cattle require staggering amounts. At some point water use pressure will be such that very hard choices will have to be made.
Dr.JC-S (laughs) You can say that. I’m not allowed to say that.
I’m actually speaking on a panel at the World Water Forum next week looking at drying rural areas and local adaptations to climate change. We’ll be looking at approaches that have been used all over the world by rural agriculturists to deal with drought and drying landscapes. I’ll be discussing irrigation efficiency and rainwater collection.
We’re going to have to get more creative in the future.
That’s an understatement!
Dr.JC-S We have no choice.
Thank you, Juliet.
Dr.JC-S You’re welcome.
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