This document summarizes research using a 3D hydrodynamic model to study the impacts of potential sea level rise on salinity in the San Francisco Bay-Delta. The model was used to simulate different levels of sea level rise from 0-167cm. Results showed sea level rise would increase salinity intrusion, requiring the management metric X2 to move further upstream. Under higher sea level rise, wet year conditions resembled dry year conditions today. More freshwater releases would be needed to maintain water quality standards like X2, posing challenges especially during dry periods.

1. Rosanne Martyr-Koller1
L. Lucas2, N. Knowles2, M. van der Wegen3, J. Helly1
1 University of California – San Diego, La Jolla, CA, USA
2 United States Geological Survey, Menlo Park, CA, USA
3 UNESCO-IHE, Delft, Netherlands

2. 3D Modeling of potential sea level rise impacts on San
Francisco Bay-Delta salinity
2

3. *Definition: the distance
between Golden Gate
Bridge and the daily 2psu
isohaline at the bottom of
the water column.
*Invented to track low
salinities.
3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
3
X2=47km X2=77km

4. *The position of X2 is managed at the State level as a water quality
metric.
(Federal Register, Vol. 59, Issue 4, January 6, 1994)
3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
4
*X2 must be positioned at
or downstream of these
locations for a required
number of days in the
spring (February-June).
*Freshwater from
reservoirs is released (if
available) to keep X2 at
these positions.

5. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
5
*Projected California sea level rise: 167cm by 21001
*Alter present-day salinity distribution and extent
*How will X2 respond to freshwater flows
under the influence of sea level rise?
1 State of California sea-level rise guidance
document, 2013

6. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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*Software: Delft3D-FM
*Developed by Deltares, Inc.
*3D finite volume
hydrodynamics model
*Unstructured
implementation of Delft3D
*Calibrated and validated
through CASCaDE II project
*Tidally-driven
waterlevels at
Pacific Ocean
*Variable
freshwater flows
*Pumps
*Gates and dams
Petaluma
Sonoma Napa
Sacramento
Mokelumne &
Cosumnes
American
San Joaquin
Yolo

7. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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*Study period: Water Year 2011(wet year) & Water Year 2012 (dry year)
*Modeled X2
showed good
agreement
with other
estimates.

8. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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*Six 2-yr simulations: 1 base case (SLR=0cm), and 5 cases
using SLR amounts shown below.

9. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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SLR (cm)
Mean X2 (km)
WET YEAR DRY YEAR
2011 2012
0 68.2 75.6
33 70.7 76.8
67 72.5 78.0
100 73.9 79.8
134 75.1 81.4
167 76.5 82.9

10. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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SLR (cm)
Mean X2 (km)
WET YEAR DRY YEAR
2011 2012
0 68.2 75.6
33 70.7 76.8
67 72.5 78.0
100 73.9 79.8
134 75.1 81.4
167 76.5 82.9
∆ Mean X2 (km)
WET
YEAR
DRY
YEAR
8.3 7.3

11. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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SLR (cm)
Mean X2 (km)
WET YEAR DRY YEAR
2011 2012
0 68.2 75.6
33 70.7 76.8
67 72.5 78.0
100 73.9 79.8
134 75.1 81.4
167 76.5 82.9

12. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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WET YEAR (2011)
February 1 – June 30
DRY YEAR (2012)
February 1 – June 30

13. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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Regulatory Req. Sea Level Rise
Position Spring Req. 0cm 33cm 67cm 100cm 134cm 167cm
<64 133 days
<74 148 days
<81 150 days
WET
YEAR
(2011)
Regulatory Req. Sea Level Rise
Position Spring Req. 0cm 33cm 67cm 100cm 134cm 167cm
<64 33 days
<74 116 days
<81 150 days
DRY
YEAR
(2012)
Regulation Source: Federal Register,
Vol. 59, Issue 4, January 6, 1994;
FR Doc No.: 94-120

14. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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For a desired X2, e.g.
55 km:
Current day needs ~
1500 m3/s of
freshwater.
SLR=167cm needs at
least twice that
amount of freshwater.

15. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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*Sea level rise will increase salinity intrusion in SF Bay-
Delta.
*Future X2 under wet conditions resembles contemporary
X2 under drought conditions.
*More freshwater is needed to keep X2 downstream
which poses challenges in dry conditions.
_
_

16. 3D Modeling of potential sea level rise impacts
on San Francisco Bay-Delta salinity
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*CASCaDE Team Lisa Lucas, Noah Knowles, John Helly, Mick van der Wegen,
Fernanda Achete, Bruce Jaffe, Theresa Fregoso, Wim Kimmerer
*Deltares, inc.
*USGS  Jim Cloern, Tara Schraga, Charles Martin, Erica Nejad, Jan Thompson, Larry
Brown
*Funding for this research is provided by the Delta Stewardship Council/Delta Science
Program and USGS Priority Ecosystems Science