Biology Reference
In-Depth Information
Winter floods will get larger and more frequent, straining already
poorly maintained levees. Soils will retain less moisture through the dry
summer, making it tougher for farmers to ripen crops, for gardeners to
maintain landscaping, and for salmon to compete with human users for
increasingly limited freshwater supplies.
According to the USGS team, the hydrological cycle is intensifying.
Wet episodes are becoming wetter and dry episodes drier. California may
soon return to the long and frequent droughts the state experienced before
the more temperate twentieth century.
The team, led by Jim Cloern, launched their project in 2006 and named
it “CASCaDE.” The acronym stands for Computational Assessments of
Scenarios of Change for the Delta Ecosystem, and it evokes the cascade of
effects climate change may have on habitats, species, water supply, and
ecology. “CASCaDE looks at the atmosphere, at the watershed, at the riv-
ers, the delta, the bay, and the ocean as one, coupled system,” says Cloern.
“These models link different landscape components with historic data on
flows, reservoirs, salinity, and fish habitat. It's one of the first attempts to
tackle the complex interactions of the whole system with climate change.”
The team is excited about some of its results. In the first layer of com-
puter work, the USGS's Mike Dettinger figured out how to tie coarse out-
puts from global climate models to local historic weather station data in
order to create a finer resolution output. The result of this “downscaling”
endeavor is a synthetic weather record for the state over the next hundred
years, projecting daily minimum and maximum air temperature, sunlight,
wind speed and direction, and relative humidity.
Colleague Noah Knowles modeled impacts of climate change on snow
storage and the timing of melt and runoff through the delta, among other
things, and linked them to other hydrodynamic processes such as ocean
tides. He also delved into the potential for extreme events in the very near
future: “This year's 100-year flood is tomorrow's yearly high tide,” he says.
In other words, water levels Bay Area inhabitants might now experience
only once every hundred years will lap at local shores once every year as
early as 2050.
These inundations may be a little different from what people might ex-
pect. “It's not like a big flood from a storm, in which the river swells and
then recedes over a period of days or weeks. It will be more like a peak
comes once a day with the high tide,” says another USGS member of the
team, Dan Cayan. But the amount of time shores may be engulfed in water
may well change from tens of hours to hundreds of hours per year within
50 years. Duration of flooding is important—the longer a coast or shore is
inundated, the more it will erode. Cayan, who also heads up climate re-
search at the Scripps Institution, examined how ocean and atmospheric
events like low-pressure zones, El Niños, and longer term climate oscilla-
