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San Francisco Bay Hydrodynamics
Project
Chief: Jon Burau
This project studies the hydrodynamics of San Francisco Bay and the Sacramento-San
Joaquin Delta. The Bay/Delta region is located at the confluence of the
Sacramento and San Joaquin Rivers. This region is a geometrically complex
network of tidally affected subembayments, channels, and sloughs. The
Delta is a critical component of the State and Federal water delivery
system, providing the hydraulic connection between surface water supplies
in northern California with farms and cities south of the Delta. The Bay
and Delta also must function as an ecosystem, providing life support to
a broad range of estuarine and fresh water fish species. Over 20 million
Californians depend on fresh-water exports from the Delta; over 4.5 million
acres of farmland are irrigated by Delta waters; and several endangered
or threatened fisheries depend on the Bay and Delta ecosystem. Unfortunately
the need to move water through the Delta has increasingly come into conflict
with maintaining a healthy ecosystem. For example, populations of a number
of pelagic (open-water) fish species have precipitously declined in the
last year and water project operations are one of the suspected reasons
for these declines.
Water project operations influence the Delta's aquatic environment primarily
by altering the flow distributions within the system. Therefore, the influence
water project operations have on many of the things people care about
(such as: the temperature and salt fields, the base of the food web, resident
and migratory fishes) are a direct consequence of the way in which water
project operations alter the flow patterns in the Delta. This project
conducts studies that specifically assess the influence the water projects
have on flow patterns in the Delta. This project not only investigates
the influence that reservoir releases, gate operations, barrier placements,
and exports have on the Delta, but also places these changes in the context
of natural modes of variability such as the tides, unregulated river flows,
and meteorological influences. Understanding the relative influence of
these natural and anthropogenic influences on flow patterns in the Delta
is crucial for managing the transport of fresh water across the Delta,
managing water quality distributions (especially salinity), and managing
biological resources and ecological function within this system. Management
agencies are considering a handful of significant structural and operational
changes in the Delta; among them a Through Delta Facility (TDF), revisions
in gate operations for the Delta Cross Channel (DCC), modifications to
Franks Tract, increasing the pumping capacity of the State Water Project
to 8500 cubic feet per second, and installing of new operable barriers
in the south Delta. The estimated costs of these proposed modifications
are collectively in the billions. This project is directly involved in
research associated with each of these proposed modifications and is taking
the lead in investigations of the first three.
The objective of this program is to conduct hydrodynamic research in
the Bay and Delta and to provide information to our cooperators, the public,
and the professional scientific community in the form of data, technical
reports, journal articles, and conference presentations.
This project conducts hydrodynamic transport investigations, in collaboration
with a broad coalition of state and federal agencies (DWR, SWRCB, DFG,
USBR, and USFWS), by using a combination of three components: Delta Flows
Monitoring, Process-Based Field studies and Three-dimensional Modeling.
The Delta Flows Network provides long-term flow data at 21 stations throughout
the Delta; the Process-Based Field Studies make detailed measurements
in certain areas of the Bay/Delta to address specific research/management
questions; and the Three-Dimensional (3D) Modeling component studies processes
that cannot be measured in the field, provides results where field observations
are sparse, and predicts system response to proposed physical and operational
changes.
SI3D is a fully 3D, transient hydrodynamic model used in the San Francisco
Bay/Delta and elsewhere. The development of the 3D code is ongoing and
both the hydrodynamic and particle-tracking models continue to be refined
and revised as necessary. The model is used to investigate distributions
of the threatened fish species, delta smelt, in the South Delta. This
study examines the effects of south Delta pumping on the transport of
fish within the delta, defines a ?zone of influence? for the pumps, and
seeks ways of minimizing entrainment of fish in the export facilities.
This application is critical as the State of California and Federal governments
weigh the costs and benefits of changes in exports and operations, and
potential modifications to the Frank?s Tract region. Ongoing 3D modeling
investigations of low dissolved oxygen conditions in the Stockton Deep
Water Ship Channel and of fish entrainment into the Delta Cross Channel
are in progress and reports are being written. Evidence of the stature
of SI3D in the science community is given by the increasing number of
users outside the USGS including: UC Davis, Cornell University, Stanford
University, University of Granada (Spain), and Australian researchers.
Within the USGS surface-water research discipline, the development of
improved capabilities for 3D surface-water modeling has been identified
as a top priority.
This project also will continue to develop graphics and visualization
software that are generally applicable. The software products from the
project are now being used in at least six other USGS science centers
and by users outside the USGS.
Process-Based Field Studies: The field studies component has investigated
a diverse range of critical issues throughout the Bay and Delta. Detailed
field studies are conducted in Suisun Marsh, North Delta, Frank?s Tract,
and South Delta. These process-based, interagency and interdisciplinary
studies are specifically addressing issues associated with ecosystem integrity
and restoration (for example, shallow water habitat regions; tidal and
intertidal marsh habitats; and anadromous and resident fish migration
and distribution), and human health issues (for example, water quality).
Examples of studies include: the Frank?s Tract Studies, investigating
the impacts of hydrodyanamics on water quality in the Central and South
Delta and fish migration through this complex region; and the South Delta
Studies, investigating the impacts of export operations on water quality,
water levels, and delta smelt distributions.
Delta Flows: This project began measuring the flows in the Delta in 1987.
The network has been expanding since then, and now is comprised of 21
continuously operating flow stations. Plans are to expand the network
to 29 stations. These data are used on a daily basis by the water project
operators and are used as a framework for understanding how the tidal
currents, river inflows, water project exports, temporary barriers, and
DCC gate operations impact transport within the upper estuary. These data
are also used routinely for numerical model calibration and validation
and are regularly leveraged into large interdisciplinary process-based
studies. These data have been presented to a wide audience including scientists,
managers, and the general public in a number of forums including technical
briefings, public forums, scientific conferences, and journal articles.
Contact Information:
Jon Burau
Office phone: 916-278-3000
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