Yolo Bypass Study
- Feasibility Studies
- Site Characterization
|| Yolo Bypass, CA (West of Sacramento, CA), Cache Creek,
- Correlation of Optical Backscatter Data with Total Mercury
Concentrations to Estimate Mercury Loads
- Engineered Floodplain
- Levees, Weirs
||Metals, Mercury; Loss of Habitat
is also a Major Issue
The increasing urbanization of land and channelization of rivers
in the San Francisco Bay area has resulted in a loss of floodplains
that provided habitat for the abundant fish populations in the Bay.
As fish habitat decreased and contamination from human activities
increased, the number of fish in the once-thriving Bay has declined.
CALFED, a consortium of state,
federal, and local agencies, has undertaken a multiyear effort to
not only restore the fish populations in the Bay, but to solve other
ecological problems as well.
The Yolo Bypass is a 60-kilometer long, 24,000 hectares, leveed
floodplain. The Bypass was originally designed in the early 1900s
to divert the flood waters of the Sacramento River away from Sacramento,
CA, and other communities, and into a broad floodplain. Most of
the Bypass was completed by the early 1930s by the U.S. Army Corps
of Engineers. This engineered floodplain is now the largest remaining
floodplain in the Sacramento River watershed. The Bypass is important
to the greater San Francisco Bay ecosystem because it more than
doubles the shallow water habitat needed by many species of fish
for spawning, and it provides key habitat for migrating waterfowl.
This vital habitat is threatened by mercury contamination. Scientists
have measured elevated mercury concentrations in flood waters in
Cache Creek, the Yolo Bypass, and the Sacramento River Delta. Cache
Creek watershed is the site of abandoned mercury mines and it discharges
into the Bypass.
To help provide the scientific information to address the above
issues, USGS scientists and their colleagues have undertaken two
studies. First, the scientists are studying what forms of mercury
are being transported into and through the Yolo Bypass and are developing
methods to estimate the loads of mercury and methyl mercury that
flow into the Yolo Bypass from Cache Creek. The information from
this study will help resource mangers address issues of mercury
bioavailability in the vital shallow-water fish and waterfowl habitat
in the Bypass.
Second, the California Department of Water Resources and CALFED
are investigating ways to use the Bypass to help restore the fisheries
of the greater San Francisco Bay ecosystem. USGS scientists and
their collaborators are studying the hydrodynamics and ecology of
the San Francisco Bay, the Sacramento River, and the Yolo Bypass.
These studies have shown that:
- Increasing the connectivity between the Sacramento River and
the Bypass could possibly allow the Bypass to be used as a corridor
for migration to and from spawning areas in the upper parts of
the Sacramento River watershed.
- Maintaining a certain minimum level of flow through the Bypass
is needed to assure water of sufficient quality to support fish
during the critical spring and fall months when fish are attracted
to the Bypass.
- Increasing the acreage of the natural floodplain habitat (shallow
water habitat) in the Bypass could result in increased fish populations.
The results from these studies are being considered by CALFED as
part of its effort to increase the ecological health of the San
Francisco Bay watershed, and to manage the competing uses of the
Bypass (fishery, wildlife habitat, agricultural production, and
flood control) in an ecologically sound and beneficial way.
||James Kuwabara, USGS, National Research Program, Menlo
- Sommer, T., Harrell, B., Nobriga, M., Brown, R., Moyle, P.,
Kimmerer, W., and Schemel, L.,
- California's Yolo Bypass--Evidence that flood control can be
compatible with fisheries, wetlands, wildlife, and agriculture:
Fisheries, vol. 26, no. 8, p. 6-16.
USGS Studies Related to Mercury Remediation
San Francisco Bay Information
Back to Toxics Program Remediation Activities Index