2007 Silicon Valley Projections - Silicon Valley Leadership Group

Environment
The Delta
The Sacramento/San Joaquin River Delta provides much of
Silicon Valley’s and two thirds of the state’s population with
drinking and irrigation water. The Delta is also a rich ecosystem
and provides the state with fisheries, agricultural and
recreational resources. However, the Delta system is under
stress and there are some serious threats to be addressed.
Levees
There are more than 1100 miles of levees in the Delta. Levees
are a critical part of the Delta’s structure and ensure that residential
and agricultural lands are protected from flooding, and
that salt water from the San Francisco Bay is not drawn into
the Delta where it can contaminate drinking and irrigation
water. However, there are several stresses on delta levees all
adding up at once. According to Dr. Jeffrey Mount, of UC
Davis, the Delta ‘looses ground’ due to soil decomposition,
subsidence and erosion at a rate of 23,000 cubic meters of
additional space below sea level every day. Some parts of the
Delta are approaching 20 feet below sea level. As this volume
of below sea level space increases, more and more pressure is
put on the levees. Because it is not possible to stop these
changes, California will eventually face some difficult and
costly choices about how to manage the delta and the levees
that protect people, infrastructure, property and water supply
resources.
According to the Department of Water Resources, both the
federal Central Valley Project and the State Water Project,
built to deliver water to millions of Californians, are dependent
on fragile Delta levees to protect water supply and water
quality.
State highways, railroad lines, water supply pipelines that
serve much of the San Francisco Bay area, energy transmission
lines, and petroleum pipelines now cross the Delta, and rely
on the continued stability of Delta levees. All together, more
than $47 billion in infrastructure is protected by central valley
levees.
In addition to the concerns regarding levees, the Delta is also
facing fishery ecosystem deterioration and declining water
quality. While the detailed analysis as to the causes of these
challenges is still underway, some known pressures on the
Delta include; increased urban and agricultural run-off,
impacts of invasive species, fresh water diversions/lower flowthrough
volumes, and changes in seasonal flow patterns as rain
replaces snow in the Sierras and spring thaws come earlier and
faster due to global warming.
The Department of Water Resources has recently begun a
study of the long term risks and possible mitigations or adaptation
strategies for the Delta. With better information about
the long term risks facing this vital resource, Silicon Valley
and the state will be able to better prepare for the future.
The Hetch Hetchy System
Almost 100 years ago, the City and County of San Francisco
implemented an unprecedented water supply project that conveyed
water over 200 miles from the Sierras to the City of San
Francisco by gravity power alone. The project flooded a pristine
valley in a national park, but also provided a secure supply
of very high quality water and electricity to San Francisco
and many other communities in the Bay Area.
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