Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

By Jay I. Cuetara, Jon R. Burau, and David H. Schoellhamer

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report

Prepared in cooperation with the

01-4086

CALIFORNIA DEPARTMENT OF WATER RESOURCES and the

U.S. BUREAU OF RECLAMATION

3021

-14

Sacramento, California2001

U.S. DEPARTMENT OF THE INTERIOR GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased from:

District Chief U.S. Geological Survey U.S. Geological Survey Information Services Placer Hall, Suite 2012 Box 25286 6000 J Street Federal Center Sacramento, CA 95819-6129 Denver, CO 80225

CONTENTS

Abstract ................................................................................................................................................................................. 1Introduction .......................................................................................................................................................................... 1

Purpose and Scope ...................................................................................................................................................... 3Study Area .................................................................................................................................................................. 6

Geographic Setting ........................................................................................................................................... 6Tides ................................................................................................................................................................. 6Currents ............................................................................................................................................................ 7Hydrologic Conditions ..................................................................................................................................... 7Meteorological Conditions ............................................................................................................................... 9Sediment ............................................................................................................................................................ 10

Acknowledgments ...................................................................................................................................................... 10Findings ................................................................................................................................................................................ 11

Tidal Timescale Variability ......................................................................................................................................... 11Currents ............................................................................................................................................................ 11Salinity .............................................................................................................................................................. 11

Residual Timescale Variability ................................................................................................................................... 12Currents ............................................................................................................................................................ 12Salinity .............................................................................................................................................................. 14

Affect of Folsom Dam Spillway Gate Failure on Suisun Bay Hydrodynamics ......................................................... 19Sediment Transport...................................................................................................................................................... 19

Summary................................................................................................................................................................................ 22References Cited ................................................................................................................................................................... 22Appendix A: Data Reduction Details and Data Presentation ................................................................................................ 27

Data Reduction Details ............................................................................................................................................... 28Acoustic Doppler Current Profiler Data ..................................................................................................................... 28Sea-Level Data ............................................................................................................................................................ 28Salinity Data ............................................................................................................................................................... 28Conductivity-Temperature Sensors ............................................................................................................................. 29Conductivity-Temperature-Depth-Optical Backscatterance Sensors ......................................................................... 29Salinity Computation .................................................................................................................................................. 29Suspended-Solids Concentration Computation ........................................................................................................... 31File Formats ................................................................................................................................................................ 31Time-Series File Format ............................................................................................................................................. 32Acoustic Doppler Current Profiler File Format ........................................................................................................... 34Data Presentation ........................................................................................................................................................ 35Plotting of Oceanographic Data ................................................................................................................................. 36Low-Pass Filter ........................................................................................................................................................... 36Harmonic Analysis ..................................................................................................................................................... 36

Appendix B—Station BEN ................................................................................................................................................... 39Appendix C—Station BULLS............................................................................................................................................... 51Appendix D—Station CARQ ................................................................................................................................................ 63Appendix E—Station MET .................................................................................................................................................. 69Appendix F—Station CUT ................................................................................................................................................... 75Appendix G—Station GARN................................................................................................................................................ 89Appendix H—Station GARNW ............................................................................................................................................ 93Appendix I—Station GC ....................................................................................................................................................... 101Appendix J—Station GDOL ................................................................................................................................................. 109Appendix K—Station GS ..................................................................................................................................................... 119

Contents III

Appendix L—Station HC ..................................................................................................................................................... 127Appendix M—Station HDOL............................................................................................................................................... 135Appendix N—Station HS ..................................................................................................................................................... 145Appendix O—Station MAL ................................................................................................................................................. 153Appendix P—Station MART ............................................................................................................................................... 163Appendix Q—Station MID .................................................................................................................................................. 171Appendix R—Station MOTH ............................................................................................................................................... 187Appendix S—Station RYER ................................................................................................................................................ 195Appendix T—Station RYERE .............................................................................................................................................. 199Appendix U—Station SPOON.............................................................................................................................................. 209Appendix V—Station WICK ................................................................................................................................................ 217

FIGURES

1–3. Maps showing: 1. San Francisco Bay Estuary, California .......................................................................................................... 22. Data-collection locations and station names, Suisun Bay, California............................................................ 33. Numerical model simulation of depth-averaged tidal current velocities in Suisun Bay, California, during

ebb current...................................................................................................................................................... 74,5. Graphs showing:

4. Delta outflow (DAYFLOW) estimates for A, 1995; B, 1994; C, 1993; and D, during the time when instruments were deployed in Suisun Bay, California............................................................ 8

5. A, barometric pressure; B, wind direction; C, wind speed; D, air temperature; and E, visible light at Station Channel Marker 27 in Suisun Bay, California, May 12, 1995, through November 6, 1995.......................... 9

6,7. Maps showing:6. Near-surface tidal currents obtained from harmonic analysis of acoustic Doppler current profiler

measurements in Suisun Bay, California ....................................................................................................... 127. Near-bed tidal currents obtained from harmonic analysis of point-velocity measurements in Suisun Bay,

California ....................................................................................................................................................... 138–14. Graphs showing:

8. Time-series plot of A, salinity, B, depth-averaged along-channel (axial) current speed, and C, verticalsalinity stratification collected at Station CUT in Suisun Bay, California..................................................... 14

9. Longitudinal and transverse residual currents at Station BULLS near Bulls Head in Suisun Bay, California, June 1, 1995, through September 19, 1995.................................................................................................... 15

10. Three-dimensional perspective view of residual current profiles measured by an acoustic Doppler current profiler near Bulls Head in Suisun Bay, California on A, Julian day 175 and B, Julian day 240 .................. 16

11. Time-series plots of A, DAYFLOW and the near-bed residual along-channel or axial currents at B, Stations BEN and BULLS; C, Stations RYER and CUT; and D, Stations MID and MAL, in Suisun Bay, California, May 30, 1995, through October 27, 1995.................................................................................... 17

12. Time-series plot of Station CUT, Suisun Bay, California; A, DAYFLOW, B, depth-averaged along-channel(axial) current speed; C, root-mean-squared current speed, D, tidally averaged near-bed and near-surfacesalinity, and E, tidally filtered vertical salinity stratification.......................................................................... 18

13. Time-series plot of A, DAYFLOW, the tidally averaged, depth-averaged along-channel (axial) current speed at B, Station MAL, C, Station CUT, and D, Station BULLS in Suisun Bay, California ..................... 20

14. Time-series plot of A, DAYFLOW, B, tidally averaged salinity at Stations BULLS, MART, and MOTH, and C, root-mean-squared depth-average current speed in Suisun Bay, California....................................... 21

A1. Example time-series file format ........................................................................................................................... 32A2. Example acoustic Doppler current profiler file format ........................................................................................ 34B1. Diagram showing configuration of instrument deployment, Station BEN, May 20 through

October 31, 1995, Suisun Bay, California ........................................................................................................... 40B2–B11. Graphs showing:

B2. Time-series plots of A, temperature; and B, salinity, Station BEN, May 20 through October 31, 1995, Suisun Bay, California ................................................................................................................................... 41

IV Contents

B3. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station BEN, May 20 through October 31, 1995, Suisun Bay, California ..................................................................................................... 41

B4. Time-series plots of A, depth; B, temperature; and C, salinity, Station BEN, June 1 through October 23, 1995, Suisun Bay, California ......................................................................................................................... 42

B5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station BEN, June 1 through October 23, 1995, Suisun Bay, California ........................................................................................ 43

B6. Time-series plots of A, temperature; and B, salinity, Station BEN, May 20 through October 31, 1995, Suisun Bay, California ................................................................................................................................... 44

B7. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station BEN, May 20 through October 31, 1995, Suisun Bay, California ..................................................................................................... 44

B8. Time-series plots of tidal currents, Station BEN, May 20 through October 31, 1995, Bin 1 near-bottom bin,Suisun Bay, California ................................................................................................................................... 45

B9. Time-series plots of tidal currents, Station BEN, May 20 through October 31, 1995, Bin 9 near-surface bin,Suisun Bay, California ................................................................................................................................... 45

B10. Longitudinal and transverse residual currents, Station BEN, May 20 through October 31, 1995, Suisun Bay, California ................................................................................................................................... 46

B11. Residual currents, Station BEN, May 20 through October 31, 1995, Suisun Bay, California....................... 47C1. Diagram showing configuration of instrument deployment, Station BULLS, June 1 through October 23, 1995,

Suisun Bay, California ......................................................................................................................................... 52C2–C9. Graphs showing:

C2. Time-series plots of A, depth; B, temperature; and C, salinity, Station BULLS, June 1 through September 19, 1995, Suisun Bay, California ................................................................................................. 53

C3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station BULLS, June 1 through September 19, 1995, Suisun Bay, California.................................................................................... 54

C4. Time-series plots of A, depth; B, temperature; and C, salinity, Station BULLS, June 1 through October 23, 1995, Suisun Bay, California ..................................................................................................... 55

C5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station BULLS, June 1 through October 23, 1995, Suisun Bay, California ........................................................................................ 56

C6. Time-series plots of tidal currents, Station BULLS, June 1 through September 19, 1995, Bin 1 near-bottom bin, Suisun Bay, California ............................................................................................................................ 57

C7. Time-series plots of tidal currents, Station BULLS, June 1 through September 19, 1995, Bin 19 near-surface bin, Suisun Bay, California ............................................................................................................................ 57

C8. Longitudinal and transverse residual currents, Station BULLS, June 1 through September 19, 1995, Suisun Bay, California ............................................................................................................................................... 58

C9. Residual currents, Station BULLS, June 1 through September 19, 1995, Suisun Bay, California................ 59D1. Diagram showing configuration of instrument deployment, Station CARQ, June 5 through

November 1, 1995, Suisun Bay, California ......................................................................................................... 64D2–D9. Graphs showing:

D2. Time-series plots of A, temperature; and B, salinity, Station CARQ, July 7 through August 27, 1995, Suisun Bay, California ................................................................................................................................... 65

D3. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station CARQ, July 7 through August 27, 1995, Suisun Bay, California....................................................................................................... 65

D4. Time-series plots of A, depth; B, temperature; and C, salinity, Station CARQ, June 5 through November 1, 1995, Suisun Bay, California.................................................................................................... 66

D5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station CARQ, June 5 through November 1, 1995, Suisun Bay, California ...................................................................................... 67

E1–E5. Graphs showing: E1. Time-series plot of Delta outflow, May 30 through October 27, 1995, Suisun Bay, California .................... 70E2. Time-series plots of A, wind speed; B, wind direction; and C, maximum wind speed, Station Channel

Marker 27, May 30 through October 27, 1995, Suisun Bay, California ........................................................ 70E3. Time-series plots of low-pass-filtered A, wind speed; B, wind direction; and C, maximum wind speed,

Station Channel Marker 27, May 30 through October 27, 1995, Suisun Bay, California ............................. 71E4. Time-series plots of A, air temperature; B, atmospheric pressure; and C, visible light, Station Channel

Marker 27, May 30 through October 27, 1995, Suisun Bay, California ........................................................ 72

Contents V

E5. Time-series plots of low-pass-filtered A, air temperature; B, atmospheric pressure; and C, visible light, Station Channel Marker 27, May 30 through October 27, 1995, Suisun Bay, California ............................. 73

F1. Diagram showing configuration of instrument deployment, Station CUT, July 7 through October 23, 1995, Suisun Bay, California ......................................................................................................................................... 76

F2–F11. Graphs showing: F2. Time-series plots of A, depth; B, temperature; and C, salinity, Station CUT, July 7 through

October 23, 1995, Suisun Bay, California ..................................................................................................... 77 F3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station CUT, July 7

through October 23, 1995, Suisun Bay, California ........................................................................................ 78 F4. Time-series plots of A, depth; B, temperature; and C, salinity, Station CUT, July 7 through

October 23, 1995, Suisun Bay, California ..................................................................................................... 79 F5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station CUT, July 7

through October 23, 1995, Suisun Bay, California ........................................................................................ 80 F6. Time-series plot of suspended-solids concentration at Station CUT, July 7 through October 23, 1995,

Suisun Bay, California ................................................................................................................................... 81 F7. Time-series plots of tidal currents, Station CUT, May 31 through October 23, 1995, Bin 1 near-bottom bin,

Suisun Bay, California ................................................................................................................................... 82 F8. Time-series plots of tidal currents, Station CUT, May 31 through October 23, 1995, Bin 6 near-surface bin,

Suisun Bay, California ................................................................................................................................... 82 F9. Longitudinal and transverse residual currents, Station CUT, May 31 through October 23, 1995,

Suisun Bay, California ................................................................................................................................... 83 F10. Residual currents, Station CUT, May 31 through October 23, 1995, Suisun Bay, California....................... 84 F11. Calibration curve for optical backscatterance sensor at Station CUT, July 7 through October 23, 1995,

Suisun Bay, California ................................................................................................................................... 85 G1. Diagram showing configuration of instrument deployment, Station GARN, July 5 through October 22, 1995,

Suisun Bay, California ......................................................................................................................................... 90 G2–G5. Graphs showing:

G2. Time-series plots of A, temperature; and B, salinity, Station GARN, July 5 through October 22, 1995, Suisun Bay, California ................................................................................................................................... 91

G3. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station GARN, July 5 through October 22, 1995, Suisun Bay, California ..................................................................................................... 91

G4. Time-series plots of A, temperature; and B, salinity, Station GARN, July 5 through October 22, 1995, Suisun Bay, California ................................................................................................................................... 92

G5. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station GARN, July 5 through October 22, 1995, Suisun Bay, California ..................................................................................................... 92

H1. Diagram showing configuration of instrument deployment, Station GARNW, September 18 through October 23, 1995, Suisun Bay, California ........................................................................................................... 94

H2–H8. Graphs showing: H2. Time-series plots of A, depth; B, temperature; and C, salinity, Station GARNW, September 18

through October 23, 1995, Suisun Bay, California ........................................................................................ 95 H3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity,

Station GARNW, September 18 through October 23, 1995, Suisun Bay, California.................................... 96 H4. Time-series plot of suspended-solids concentration at Station GARNW, September 18

through October 23, 1995, Suisun Bay, California ........................................................................................ 97 H5. Time-series plots of tidal currents, Station GARNW, September 18 through October 23, 1995,

Suisun Bay, California ................................................................................................................................... 97 H6. Longitudinal and transverse residual currents, Station GARNW, September 18 through

October 23, 1995, Suisun Bay, California ..................................................................................................... 98 H7. Residual currents, Station GARNW, September 18 through October 23, 1995,

Suisun Bay, California ................................................................................................................................... 98 H8. Calibration curve for near-bottom optical backscatterance sensor at Station GARNW,

September 18 through October 23, 1995, Suisun Bay, California ................................................................. 99

VI Contents

I1. Diagram showing configuration of instrument deployment, Station GC, July 4 through August 18, 1995, Suisun Bay, California ......................................................................................................................................... 102

I2–I8. Graphs showing: I2. Time-series plots of A, depth; B, temperature; and C, salinity, Station GC, July 4 through

August 18, 1995, Suisun Bay, California....................................................................................................... 103 I3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station GC, July 4

through August 18, 1995, Suisun Bay, California.......................................................................................... 104 I4. Time-series plot of suspended-solids concentration at Station GC, July 4 through August 18, 1995,

Suisun Bay, California ................................................................................................................................... 105 I5. Time-series plots of tidal currents, Station GC, July 4 through August 18, 1995, Suisun Bay, California ... 105 I6. Longitudinal and transverse residual currents, Station GC, July 4 through August 18, 1995,

Suisun Bay, California ................................................................................................................................... 106 I7. Residual currents, Station GC, July 4 through August 18, 1995, Suisun Bay, California ............................. 106 I8. Calibration curve for near-bottom optical backscatterance sensor, Station GC, July 4 through

August 18, 1995, Suisun Bay, California....................................................................................................... 107 J1. Diagram showing configuration of instrument deployment, Station GDOL, July 6 through

September 18, 1995, Suisun Bay, California ....................................................................................................... 110 J2–J10. Graphs showing:

J2. Time-series plots of A, depth; B, temperature; and C, salinity, Station GDOL, July 17 through September 18, 1995, Suisun Bay, California ................................................................................................. 111

J3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station GDOL, July 17 through September 18, 1995, Suisun Bay, California.................................................................................... 112

J4. Time-series plot of suspended-solids concentration at Station GDOL, July 17 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 113

J5. Time-series plots of A, temperature; and B, salinity, Station GDOL, April 30 through November 3, 1995, Suisun Bay, California ................................................................................................................................... 113

J6. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station GDOL, April 30 through November 3, 1995, Suisun Bay, California.................................................................................................... 114

J7. Time-series plots of tidal currents, Station GDOL, July 6 through September 18, 1995, Suisun Bay, California ....................................................................................................................................................... 115

J8. Longitudinal and transverse residual currents, Station GDOL, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 115

J9. Residual currents, Station GDOL, July 6 through September 18, 1995, Suisun Bay, California.................. 116 J10. Calibration curve for near-bottom optical backscatterance sensor, Station GDOL, July 17 through

September 18, 1995, Suisun Bay, California ................................................................................................. 116 K1. Diagram showing configuration of instrument deployment, Station GS, July 6 through

September 18, 1995, Suisun Bay, California ....................................................................................................... 120 K2–K8. Graphs showing:

K2. Time-series plots of A, depth; B, temperature; and C, salinity, Station GS, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................. 121

K3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station GS, July 6 through September 18, 1995, Suisun Bay, California.................................................................................... 122

K4. Time-series plot of suspended-solids concentration at Station GS, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 123

K5. Time-series plots of tidal currents, Station GS, July 6 through September 18, 1995, Suisun Bay, California ....................................................................................................................................................... 123

K6. Longitudinal and transverse residual currents, Station GS, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 124

K7. Residual currents, Station GS, July 6 through September 18, 1995, Suisun Bay, California........................ 124 K8. Calibration curve for near-bottom optical backscatterance sensor, Station GS, July 6 through

September 18, 1995, Suisun Bay, California ................................................................................................. 125 L1. Diagram showing configuration of instrument deployment, Station HC, July 9 through October 24, 1995,

Suisun Bay, California ......................................................................................................................................... 128

Contents VII

L2–L8. Graphs showing:L2. Time-series plots of A, depth; B, temperature; and C, salinity, Station HC, July 28 through

October 24, 1995, Suisun Bay, California ..................................................................................................... 129L3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HC, July 28

through October 24, 1995, Suisun Bay, California ........................................................................................ 130L4. Time-series plot of suspended-solids concentration at Station HC, July 28 through October 24, 1995,

Suisun Bay, California ................................................................................................................................... 131L5. Time-series plots of tidal currents, Station HC, July 9 through October 24, 1995, Suisun Bay, California.. 131L6. Longitudinal and transverse residual currents, Station HC, July 9 through October 24, 1995,

Suisun Bay, California ................................................................................................................................... 132L7. Residual currents, Station HC, July 9 through October 24, 1995, Suisun Bay, California............................ 132L8. Calibration curve for near-bottom optical backscatterance sensor, Station HC, July 28 through

October 24, 1995, Suisun Bay, California ..................................................................................................... 133M1. Diagram showing configuration of instrument deployment, Station HDOL, July 6 through September 18, 1995,

Suisun Bay, California ......................................................................................................................................... 136M2–M10. Graphs showing:

M2. Time-series plots of A, depth; B, temperature; and C, salinity, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................. 137

M3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California.................................................................................... 138

M4. Time-series plot of suspended-solids concentration at Station HDOL, July 6 through September 18, 1995,Suisun Bay, California ................................................................................................................................... 139

M5. Time-series plots of A, temperature; and B, salinity, Station HDOL, April 30 through November 3, 1995, Suisun Bay, California ................................................................................................................................... 139

M6. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station HDOL, April 30 throughNovember 3, 1995, Suisun Bay, California.................................................................................................... 140

M7. Time-series plots of tidal currents, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California ....................................................................................................................................................... 140

M8. Longitudinal and transverse residual currents, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 141

M9. Residual currents, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California.................. 141M10. Burst velocity variance, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California......... 141M11. Calibration curve for near-bottom optical backscatterance sensor, Station HDOL, July 6 through

September 18, 1995, Suisun Bay, California ................................................................................................. 142N1. Diagram showing configuration of instrument deployment, Station HS, July 7 through September 18, 1995,

Suisun Bay, California ......................................................................................................................................... 146N2–N8. Graphs showing:

N2. Time-series plots of A, depth; B, temperature; and C, salinity, Station HS, August 1 through September 18, 1995, Suisun Bay, California ................................................................................................. 147

N3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HS, August 1 through September 18, 1995, Suisun Bay, California.................................................................................... 148

N4. Time-series plot of suspended-solids concentration, Station HS, August 1 through September 18, 1995,Suisun Bay, California ................................................................................................................................... 148

N5. Time-series plots of tidal currents, Station HS, July 7 through September 18, 1995, Suisun Bay, California ....................................................................................................................................................... 149

N6. Longitudinal and transverse residual currents, Station HS, July 7 through September 18, 1995, Suisun Bay, California ................................................................................................................................... 149

N7. Residual currents, Station HS, July 7 through September 18, 1995, Suisun Bay, California........................ 150N8. Calibration curve for near-bottom optical backscatterance sensor, Station HS, August 1 through

September 18, 1995, Suisun Bay, California ................................................................................................. 150O1. Diagram showing configuration of instrument deployment, Station MAL, July 6 through November 16, 1995,

Suisun Bay, California ......................................................................................................................................... 154

VIII Contents

O2–O7. Graphs showing: O2. Time-series plots of A, sea level; B, temperature; and C, salinity, Station MAL, May 8 through

October 15, 1995, Suisun Bay, California ..................................................................................................... 155 O3. Time-series plots of low-pass-filtered A, sea level; B, temperature; and C, salinity, Station MAL, May 8

through October 15, 1995, Suisun Bay, California ........................................................................................ 156 O4. Time-series plots of tidal currents, Station MAL, July 6 through November 16, 1995, Bin 1 near-bottom

bin, Suisun Bay, California ............................................................................................................................ 157 O5. Time-series plots of tidal currents, Station MAL, July 6 through November 16, 1995, Bin 19 near-surface

bin, Suisun Bay, California ............................................................................................................................ 157 O6. Longitudinal and transverse residual currents, Station MAL, July 6 through November 16, 1995,

Suisun Bay, California ................................................................................................................................... 158 O7. Residual currents, Station MAL, July 6 through November 16, 1995, Suisun Bay, California .................... 159

P1. Diagram showing configuration of instrument deployment, Station MART, May 1 through November 1, 1995, Suisun Bay, California ......................................................................................................................................... 164

P2–P5. Graphs showing: P2. Time-series plots of A, sea level; B, temperature; and C, salinity, Station MART, May 1 through

November 1, 1995, Suisun Bay, California.................................................................................................... 165 P3. Time-series plots of low-pass-filtered A, sea level; B, temperature; and C, salinity, Station MART,

May 1 through November 1, 1995, Suisun Bay, California........................................................................... 166 P4. Time-series plots of A, sea level; B, temperature; and C, salinity, Station MART, May 1 through

November 1, 1995, Suisun Bay, California.................................................................................................... 167 P5. Time-series plots of low-pass-filtered A, sea level; B, temperature; and C, salinity, Station MART, May 1

through November 1, 1995, Suisun Bay, California ...................................................................................... 168 Q1. Diagram showing configuration of instrument deployment, Station MID, June 1 through October 23, 1995,

Suisun Bay, California ......................................................................................................................................... 172 Q2–Q13. Graphs showing:

Q2. Time-series plots of A, depth; B, temperature; and C, salinity, Station MID, June 1 through July 13, 1995, Suisun Bay, California............................................................................................................ 173

Q3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station MID, June 1 through July 13, 1995, Suisun Bay, California .............................................................................................. 174

Q4. Time-series plots of A, depth; B, temperature; and C, salinity, Station MID, June 1 through October 23, 1995, Suisun Bay, California ..................................................................................................... 175

Q5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station MID, June 1 through October 23, 1995, Suisun Bay, California ........................................................................................ 176

Q6. Time-series plots of tidal currents, station MID, June 1 through August 10, 1995, Bin 1 near-bottom bin, Suisun Bay, California ............................................................................................................................ 177

Q7. Time-series plots of tidal currents, Station MID, June 1 through August 10, 1995, Bin 19 near-surface bin, Suisun Bay, California ............................................................................................................................ 177

Q8. Time-series plots of tidal currents, Station MID, August 10 through October 23, 1995, Bin 1 near-bottom bin, Suisun Bay, California........................................................................................................ 178

Q9. Time-series plots of tidal currents, Station MID, August 10 through October 23, 1995, Bin 7 near-surface bin, Suisun Bay, California........................................................................................................ 178

Q10. Longitudinal and transverse residual currents, Station MID, June 1 through August 10, 1995, Suisun Bay, California ................................................................................................................................... 179

Q11. Longitudinal and transverse residual currents, Station MID, August 10 through October 23, 1995, Suisun Bay, California ................................................................................................................................... 180

Q12. Residual currents, Station MID, June 1 through August 10, 1995, Suisun Bay, California .......................... 181 Q13. Residual currents, Station MID, August 10 through October 23, 1995, Suisun Bay, California................... 182

R1. Diagram showing configuration of instrument deployment, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California.............................................................................................. 188

R2–R8. Graphs showing: R2. Time-series plots of A, depth; B, temperature; and C, salinity, Station MOTH, September 18 through

October 23, 1995, Suisun Bay, California ..................................................................................................... 189

Contents IX

R3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ................................................................. 190

R4. Time-series plot of suspended-solids concentration at Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ..................................................................................................... 191

R5. Time-series plots of tidal currents, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ................................................................................................................................... 191

R6. Longitudinal and transverse residual currents, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ................................................................................................................................... 192

R7. Residual currents, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ......... 192R8. Calibration curve for near-bottom optical backscatterance sensor, Station MOTH, September 18

through October 23, 1995, Suisun Bay, California ........................................................................................ 193S1. Diagram showing configuration of instrument deployment, Station RYER, July 7 through August 18, 1995,

Suisun Bay, California ......................................................................................................................................... 196S2,S3. Graphs showing:

S2. Time-series plots of A, temperature; and B, salinity, Station RYER, July 7 through August 18, 1995, Suisun Bay, California ................................................................................................................................... 197

S3. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station RYER, July 7 through August 18, 1995, Suisun Bay, California....................................................................................................... 197

T1. Diagram showing configuration of instrument deployment, Station RYERE, June 1 through August 18, 1995, Suisun Bay, California............................................................................................................. 200

T2–T7. Graphs showing:T2. Time-series plots of A, depth; B, temperature; and C, salinity, Station RYERE, June 27 through

August 18, 1995, Suisun Bay, California....................................................................................................... 201T3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station RYERE,

June 27 through August 18, 1995, Suisun Bay, California ............................................................................ 202T4. Time-series plots of tidal currents, Station RYERE, June 1 through August 18, 1995, Bin 1

near-bottom bin, Suisun Bay, California........................................................................................................ 203T5. Time-series plots of tidal currents, Station RYERE, June 1 through August 18, 1995, Bin 4

near-surface bin, Suisun Bay, California........................................................................................................ 203T6. Longitudinal and transverse residual currents, Station RYERE, June 1 through August 18, 1995,

Suisun Bay, California ................................................................................................................................... 204T7. Residual currents, Station RYERE, June 1 through August 18, 1995, Suisun Bay, California ..................... 205

U1. Diagram showing configuration of instrument deployment, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California.............................................................................................. 210

U2–U8. Graphs showing:U2. Time-series plots of A, depth; B, temperature; and C, salinity, Station SPOON, September 18

through October 24, 1995, Suisun Bay, California ........................................................................................ 211U3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station SPOON,

September 18 through October 24, 1995, Suisun Bay, California ................................................................. 212U4. Time-series plot of suspended-solids concentration at Station SPOON, September 18 through

October 24, 1995, Suisun Bay, California ..................................................................................................... 213U5. Time-series plots of tidal currents, Station SPOON, September 18 through October 24, 1995,

Suisun Bay, California ................................................................................................................................... 213U6. Longitudinal and transverse residual currents, Station SPOON, September 18 through

October 24, 1995, Suisun Bay, California ..................................................................................................... 214U7. Residual currents, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California........ 214U8. Calibration curve for near-bottom optical backscatterance sensor, Station SPOON, September 18

through October 24, 1995, Suisun Bay, California ........................................................................................ 215V1. Diagram showing configuration of instrument deployment, Station WICK, April 30 through

October 31, 1995, Suisun Bay, California ........................................................................................................... 218

X Contents

V2, V3. Graphs showing:V2. Time-series plots of A, sea level; B, temperature; and C, salinity, Station WICK, April 30

through October 31, 1995, Suisun Bay, California ........................................................................................ 219V3. Time-series plots of low-pass-filtered A, sea level; B, temperature; and C, salinity, Station WICK,

April 30 through October 31, 1995, Suisun Bay, California.......................................................................... 220

TABLES

1. Data-collection instrument locations and deployment periods............................................................................... 42. Specifications for instruments used in Suisun Bay, California............................................................................... 5

A1. Principal astronomical tidal frequencies, Suisun Bay, California .......................................................................... 38B1. Harmonic analysis results from depth measurements, Station BEN, June 1 through October 31, 1995,

Suisun Bay, California ............................................................................................................................................ 48B2. Harmonic analysis results for velocity, Station BEN, May 20 through October 31, 1995, Bin 1

near-bottom bin, Suisun Bay, California ................................................................................................................ 49B3. Harmonic analysis results for velocity, Station BEN, May 20 through October 31, 1995, Bin 9

near-surface bin, Suisun Bay, California ................................................................................................................ 50C1. Harmonic analysis results from depth measurements, Station BULLS, June 1 through October 23, 1995,

Suisun Bay, California ............................................................................................................................................ 60C2. Harmonic analysis results for velocity, Station BULLS, June 1 through September 19, 1995, Bin 1

near-bottom bin, Suisun Bay, California ................................................................................................................ 61C3. Harmonic analysis results for velocity, Station BULLS, June 1 through September 19, 1995, Bin 19

near-surface bin, Suisun Bay, California ................................................................................................................ 61D1. Harmonic analysis results from depth measurements, Station CARQ, June 5 through November 1, 1995,

Suisun Bay, California ............................................................................................................................................ 68F1. Harmonic analysis results from depth measurements, Station CUT, July 7 through October 23, 1995,

Suisun Bay, California ............................................................................................................................................ 86F2. Harmonic analysis results for velocity, Station CUT, May 31 through October 23, 1995, Bin 1

near-bottom bin, Suisun Bay, California ................................................................................................................ 87F3. Harmonic analysis results for velocity, Station CUT, May 31 through October 23, 1995, Bin 6

near-surface bin, Suisun Bay, California ................................................................................................................ 88H1. Harmonic analysis results from depth measurements, Station GARNW, September 18 through

October 23, 1995, Suisun Bay, California .............................................................................................................. 100H2. Harmonic analysis results for velocity, Station GARNW, September 18 through October 23, 1995,

Suisun Bay, California ............................................................................................................................................ 100I1. Harmonic analysis results from depth measurements, Station GC, July 4 through August 18, 1995,

Suisun Bay, California ............................................................................................................................................ 108I2. Harmonic analysis results for velocity, Station GC, July 4 through August 18, 1995, Suisun Bay, California ..... 108J1. Harmonic analysis results from depth measurements, Station GDOL, July 17 through September 18, 1995,

Suisun Bay, California ............................................................................................................................................ 117J2. Harmonic analysis results for velocity, Station GDOL, July 6 through September 18, 1995,

Suisun Bay, California ............................................................................................................................................ 117K1. Harmonic analysis results from depth measurements, Station GS, July 6 through September 18, 1995,

Suisun Bay, California ............................................................................................................................................ 126K2. Harmonic analysis results for velocity, Station GS, July 6 through September 18, 1995,

Suisun Bay, California ............................................................................................................................................ 126L1. Harmonic analysis results from depth measurements, Station HC, July 28 through October 24, 1995,

Suisun Bay, California ............................................................................................................................................ 134L2. Harmonic analysis results for velocity, Station HC, July 9 through October 24, 1995, Suisun Bay, California.... 134

M1. Harmonic analysis results from depth measurements, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California ............................................................................................................................................ 143

M2. Harmonic analysis results for velocity, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California ................................................................................................................................................................ 143

N1. Harmonic analysis results from depth measurements, Station HS, August 1 through September 18, 1995, Suisun Bay, California ............................................................................................................................................ 151

Contents XI

N2. Harmonic analysis results for velocity, Station HS, July 7 through September 18, 1995, Suisun Bay, California ................................................................................................................................................................ 151

O1. Harmonic analysis results from sea-level measurements, Station MAL, May 8 through October 15, 1995, Suisun Bay, California ............................................................................................................................................ 160

O2. Harmonic analysis results for velocity, Station MAL, July 6 through November 16, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... 161

O3. Harmonic analysis results for velocity, Station MAL, July 6 through November 16, 1995, Bin 19 near-surface bin, Suisun Bay, California ................................................................................................................ 161

P1. Harmonic analysis results from sea-level measurements, Station MART, May 1 through November 1, 1995, Suisun Bay, California ............................................................................................................................................ 169

Q1. Harmonic analysis results from depth measurements, Station MID, June 1 through October 23, 1995, Suisun Bay, California ............................................................................................................................................ 183

Q2. Harmonic analysis results for velocity, Station MID, June 1 through August 10, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... 184

Q3. Harmonic analysis results for velocity, Station MID, June 1 through August 10, 1995, Bin 19 near-surface bin, Suisun Bay, California ..................................................................................................................................... 184

Q4. Harmonic analysis results for velocity, Station MID, August 10 through October 23, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... 185

Q5. Harmonic analysis results for velocity, Station MID, August 10 through October 23, 1995, Bin 7 near-surface bin, Suisun Bay, California ..................................................................................................................................... 185

R1. Harmonic analysis results from depth measurements, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California .................................................................................................................................. 194

R2. Harmonic analysis results for velocity, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ................................................................................................................................................................ 194

T1. Harmonic analysis results from depth measurements, Station RYERE, June 27 through August 18, 1995, Suisun Bay, California ............................................................................................................................................ 206

T2. Harmonic analysis results for velocity, Station RYERE, June 1 through August 18, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... 207

T3. Harmonic analysis results for velocity, Station RYERE, June 1 through August 18, 1995, Bin 4 near-surface bin, Suisun Bay, California ..................................................................................................................................... 207

U1. Harmonic analysis results from depth measurements, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California .............................................................................................................. 216

U2. Harmonic analysis results for velocity measurements, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California .............................................................................................................. 216

V1. Harmonic analysis results from sea-level measurements, Station WICK, April 30 through October 31, 1995, Suisun Bay, California ............................................................................................................................................ 221

CONVERSION FACTORS, ABBREVIATIONS, ACRONYMS, DATA-COLLECTION STATIONS, SYMBOLS, AND JULIAN DATE CALENDAR

Multiply By To obtain

centimeter (cm) 0.3937 inch centimeter per second (cm/s) 0.3937 inch per second

cubic meter per second (m3/s) 35.31 cubic foot per second decibar (dbar) 1.0197 meters of water (at 4°C)

kilometer (km) 0.6214 mile square kilometer (km2) 0.3861 square mile

meter (m) 3.281 foot meter per second (m/s) 3.281 foot per second

meter per second squared (m/s2) 3.281 foot per second squared millibar (mbar) 0.0145 pounds per square inch

millimeter (mm) 0.03937 inch square meter (m2) 10.76 square foot

Temperature in degrees Celsius (ºC) may be converted to degrees Fahrenheit (ºF) as follows: ºF = (1.8 x ºC) + 32

XII Contents

Abbreviations and Acronyms: deg, degrees

deg. C degrees Celcius deg. T, degrees true

E equilibrium argument Hz hertz

kHz, kilohertz mg/L milligram per liter

mS/CM, mS/cm, millisiemens per centimeter mmhos/cm, millimhos per centimeter

Hm micrometer HS/cm microsiemens per centimeter

ppt, parts per thousand cfs, cubic feet per second

cms, cubic meter per second ADCP, Acoustic Doppler Current Profiler

BIN, a depth cell from an ADCP CT, conductivity-temperature

CTD, conductivity-temperature-depth CTDO, conductivity-temperature-depth-optical backscatter

DAYFLOW, California Department of Water Resources delta outflow DWR, California Department of Water Resources ETM, estuarine turbidity maximum

EZ, entrapment zone FTU, formazine turbidity unit

IEP, Interagency Ecological Program for the San Francisco Bay Estuary MLLW, mean lower low water

OBS optical backscatteranced sensor RDI R.D. Instruments, Inc.

RMS, root-mean-squared SC, specific conductance

SI (System International) International System of Weights and Measures SSC suspended-solids concentration SSF suspended-solids flux

UNESCO United Nations Educational, Scientific, and Cultural Organization USBR, U.S. Bureau of Reclamation USGS, U.S. Geological Survey

Data-collection stations:

BEN BULLS

GC GDOL

MID MOTH

Tidal symbols:

J1 K1

m2 N2

CARQ MET CUT GARN GARNW

GS HC HDOL HS MAL MART

RYER RYERE SPOON WICK

K2 L2 M1 M2 M4 Mk3 Mu2 H2

Nu2 n2 O1 P1 Q1 S2 T2 v2

Contents XIII

Vertical Datum

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929), a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

All depths in this report are referenced to mean lower low water (MLLW). For the purpose of this report, the difference between MLLW and sea level is assumed to be 1.0 m within Suisun Bay.

Salinities in this report are presented without (practical salinity) units because salinity is a conductivity ratio; therefore, it has no physical units.

XIV Contents

5 5 5

10 10 10

15 15 15

20 20 20

25 25 25

30 30 30

Julian Date Calendar

For nonleap years Day Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Day

1 -30 1 32 60 91 121 152 182 213 244 274 305 335 1

2 -29 2 33 61 92 122 153 183 214 245 275 306 336 2

3 -28 3 34 62 93 123 154 184 215 246 276 307 337 3

4 -27 4 35 63 94 124 155 185 216 247 277 308 338 4

-26 36 64 95 125 156 186 217 248 278 309 339

6 -25 6 37 65 96 126 157 187 218 249 279 310 340 6

7 -24 7 38 66 97 127 158 188 219 250 280 311 341 7

8 -23 8 39 67 98 128 159 189 220 251 281 312 342 8

9 -22 9 40 68 99 129 160 190 221 252 282 313 343 9

-21 41 69 100 130 161 191 222 253 283 314 344

11 -20 11 42 70 101 131 162 192 223 254 284 315 345 11

12 -19 12 43 71 102 132 163 193 224 255 285 316 346 12

13 -18 13 44 72 103 133 164 194 225 256 286 317 347 13

14 -17 14 45 73 104 134 165 195 226 257 287 318 348 14

-16 46 74 105 135 166 196 227 258 288 319 349

16 -15 16 47 75 106 136 167 197 228 259 289 320 350 16

17 -14 17 48 76 107 137 168 198 229 260 290 321 351 17

18 -13 18 49 77 108 138 169 199 230 261 291 322 352 18

19 -12 19 50 78 109 139 170 200 231 262 292 323 353 19

-11 51 79 110 140 171 201 232 263 293 324 354

21 -10 21 52 80 111 141 172 202 233 264 294 325 355 21

22 -9 22 53 81 112 142 173 203 234 265 295 326 356 22

23 -8 23 54 82 113 143 174 204 235 266 296 327 357 23

24 -7 24 55 83 114 144 175 205 236 267 297 328 358 24

-6 56 84 115 145 176 206 237 268 298 329 359

26 -5 26 57 85 116 146 177 207 238 269 299 330 360 26

27 -4 27 58 86 117 147 178 208 239 270 300 331 361 27

28 -3 28 59 87 118 148 179 209 240 271 301 332 362 28

29 -2 29 88 119 149 180 210 241 272 302 333 363 29

-1 89 120 150 181 211 242 273 303 334 364

31 31 90 151 212 243 304 365 31

Contents XV

5 5 5

10 10 10

15 15 15

20 20 20

25 25 25

30 30 30

Julian Date Calendar—Continued

For leap years Day Dec Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Day

1 -30 1 32 61 92 122 153 183 214 245 275 306 336 1

2 -29 2 33 62 93 123 154 184 215 246 276 307 337 2

3 -28 3 34 63 94 124 155 185 216 247 277 308 338 3

4 -27 4 35 64 95 125 156 186 217 248 278 309 339 4

-26 36 65 96 126 157 187 218 249 279 310 340

6 -25 6 37 66 97 127 158 188 219 250 280 311 341 6

7 -24 7 38 67 98 128 159 189 220 251 281 312 342 7

8 -23 8 39 68 99 129 160 190 221 252 282 313 343 8

9 -22 9 40 69 100 130 161 191 222 253 283 314 344 9

-21 41 70 101 131 162 192 223 254 284 315 345

11 -20 11 42 71 102 132 163 193 224 255 285 316 346 11

12 -19 12 43 72 103 133 164 194 225 256 286 317 347 12

13 -18 13 44 73 104 134 165 195 226 257 287 318 348 13

14 -17 14 45 74 105 135 166 196 227 258 288 319 349 14

-16 46 75 106 136 167 197 228 259 289 320 350

16 -15 16 47 76 107 137 168 198 229 260 290 321 351 16

17 -14 17 48 77 108 138 169 199 230 261 291 322 352 17

18 -13 18 49 78 109 139 170 200 231 262 292 323 353 18

19 -12 19 50 79 110 140 171 201 232 263 293 324 354 19

-11 51 80 111 141 172 202 233 264 294 325 355

21 -10 21 52 81 112 142 173 203 234 265 295 326 356 21

22 -9 22 53 82 113 143 174 204 235 266 296 327 357 22

23 -8 23 54 83 114 144 175 205 236 267 297 328 358 23

24 -7 24 55 84 115 145 176 206 237 268 298 329 359 24

-6 56 85 116 146 177 207 238 269 299 330 360

26 -5 26 57 86 117 147 178 208 239 270 300 331 361 26

27 -4 27 58 87 118 148 179 209 240 271 301 332 362 27

28 -3 28 59 88 119 149 180 210 241 272 302 333 363 28

29 -2 29 60 89 120 150 181 211 242 273 303 334 364 29

-1 90 121 151 182 212 243 274 304 335 365

31 31 91 152 213 244 305 366 31

XVI Contents

Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995 By Jay I. Cuetara, Jon R. Burau, and David H. Schoellhamer

ABSTRACT

Sea level, current velocity, water temperature, salinity (computed from conductivity and temperature), and suspended-solids data collected in Suisun Bay, California, from May 30, 1995, through October 27, 1995, by the U.S. Geological Survey are documented in this report. Data were collected concurrently at 21 sites. Various parameters were measured at each site. Velocity-profile data were collected at 6 sites, single-point velocity measurements were made at 9 sites, salinity data were collected at 20 sites, and suspended-solids concentrations were measured at 10 sites. Sea-level and velocity data are presented in three forms; harmonic analysis results; time-series plots (sea level, current speed, and current direction versus time); and time-series plots of low-pass-filtered time series. Temperature, salinity, and suspended-solids data are presented as plots of raw and low-pass-filtered time series.

The velocity and salinity data presented in this report document a period when the residual current patterns and salt field were transitioning from a freshwater-inflow-dominated condition towards a quasi steady-state summer condition when density-driven circulation and tidal nonlinearities became relatively more important as long-term transport mechanisms. Sacramento–San Joaquin River Delta outflow was high prior to and during this study, so the tidally averaged salinities were abnormally low for this time of year. For example, the tidally averaged salinities varied from 0–12 at Martinez, the western border of Suisun Bay, to a maximum of 2 at Mallard Island, the eastern border of Suisun Bay.

Even though salinities increased overall in Suisun Bay during the study period, the near-bed residual currents primarily were directed seaward. Therefore, salinity intrusion through Suisun Bay towards the Delta primarily was accomplished in the absence of the tidally averaged, two-layer flow known as gravitational circulation where, by definition, the net currents are landward at the bed. The Folsom Dam spillway gate failure on July 17, 1995, was analyzed to determine the effect on the hydrodynamics of Suisun Bay. The peak flow of the American River reached roughly 1,000 cubic meters per second as a result of the failure, which is relatively small. This was roughly 15 percent of the approximate 7,000 cubic meters per second tidal flows that occur daily in Suisun Bay and was likely attenuated greatly. Based on analysis of tidally averaged near-bed salinity and depth-averaged currents after the failure, the effect was essentially nonexistent and is indistinguishable from the natural variability.

INTRODUCTION

The data described in this report were collected in cooperation with the California Department of Water Resources (DWR) and the U.S. Bureau of Reclamation (USBR) as part of ongoing research by the U.S. Geological Survey (USGS) into the hydrodynamics of the San Francisco Bay estuary (fig. 1). These

Introduction 1

122o30' 122 o00'

38o00'

37 o30'

Figure 1. San Francisco Bay Estuary, California.

DEPTH MORE THAN 2.5 METERS

Martinez C

OAST

CE

NTR

AL

RAN

GES

VALLEY

CALIFORNIA

Sacramento–San Joaquin River Delta

0

5

5

10

10

0 MILES

KILOMETERS

SOUTH BAY

CENTRAL BAY

SAN PABLO BAY

SUISUN BAY

SAN JOSE

Sui

sun

Slo

ugh

Montezum

aSlough

Mallard Island

Spoonbill Creek

Bay Bridge

Golden Gate Bridge

San Mateo Bridge

Dumbarton Bridge

San Francisco

San Francisco International

Airport

Oakland

PacificO

cean

Ship Channel

Reser

veFlee

t Cha

nnel

Carquinez Strait

Napa River

San P

ablo

Stra

it

Grizzly Bay

Honker Bay

Suisun Cut

Benicia Bridge

2 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

o38

o38

Fig

data were collected as part of the Interagency Ecological Program (IEP) sponsored interdisciplinary entrapment zone (EZ) study (Kimmerer, 1998) and USGS Place-Based Program. Other agencies involved in the IEP include the California Department of Fish and Game and the U.S. Fish and Wildlife Service. The USGS conducts a wide range of research and monitoring activities in the San Francisco Bay estuary (Cloern and others, 1995). Research includes many disciplines, including climate change (Peterson and others, 1995), hydrodynamics (Smith and others, 1995), sediment transport (Schoellhamer and others, 1997), phytoplankton dynamics (Cloern and Jassby, 1995), toxic contamination (Luoma and others, 1993; Kuivila and Foe, 1995), and exotic species (Nichols and others, 1990). For an updated list of USGS publications, see the Access USGS web site at http://sfbay.wr.usgs.gov/access/pubs.html.

Purpose and Scope

This report documents hydrodynamic and suspended-solids concentration (SSC) data collected in Suisun Bay (fig. 1) from May 30, 1995, through October 27, 1995, through plots and harmonic analysis results. Five distinct types of data were collected and analyzed; (1) sea-level data measured with a pressure sensor at depth or a surface float; (2) velocity data consisting of magnitude and direction, either at a single point or equally spaced points in the vertical, depending on the depth at each location; (3) water-temperature data, (4) salinity data calculated from measured values of conductivity and temperature; and (5) suspended-solids data collected with optical backscatterance sensors (OBS). Additionally, hydrologic and meteorological data are presented. The hydrologic data consists of the Sacramento–San Joaquin Delta outflow, and the meteorological data include measured values of barometric pressure, wind speed and direction, air temperature, and visible light.

The principal objective for collecting these data was to measure the spatial and temporal variability in the residual currents, salinity, and SSC in the channels of Suisun Bay. Acoustic Doppler current profilers (ADCPs) were deployed in the channels to vertically define the velocity structure. In order to estimate salinity and sediment fluxes, conductivity-temperature-depth-optical backscatterance (CTDO) sensors were deployed adjacent to the velocity measuring instruments, where possible. Station locations are shown in figure 2; their respective latitudes, longitudes, and deployment dates are given in table 1. The instrument specifications are presented in table 2.

o o122 15' 121 53'

10'

02'

Introduction 3

Suisun Bay

N

Grizzly Bay

Honker Bay

Chipps I. Benicia

Martinez

DEPTH MORE THAN 2.5 METERS

0

5

5

0 MILES

KILOMETERS

WICK tb

CARQ t b

MART t b

BULLS tb

RYER b

MID

RYERE b

tb

MAL t

SPOON

CUT b

HDOL

HC

HS

GDOL

GC

GS

MOTH

GARNW

GARN tb

BEN t

MET

Conductivity, Temperature, Dept h, Optical backscatterance sensor (CTDO) Conductivity, Temperature, Dept h (CTD) Conductivity, Temperature (CT) Single Point Velocity Velocity Profile (Acoustic Doppler Current Profiler)

t Top Sensor b Bottom Sensor

Instrument Descriptions

t

Site Location

ure 2. Data-collection locations and station names, Suisun Bay, California.

Table 1. Data-collection instrument locations and deployment periods [MLLW, mean lower low water; m, meters; na, not applicable; v, velocity sensor; s, salinity sensor; p, pressure sensor or sea level sensor; o, optical backscatterance sensor; nb, narrow-band acoustic Doppler current profiler; bb, broad-band acoustic Doppler current profiler]

Depth Sensor Deployment Station Name Position (MLLW In depth period

meters) (meters) (Julian Days)

BEN (nb, s, p) 38A02′37″ 18.6 m

122A07′25″

BULLS (bb, s, p) 38A02′54″ 12.3 m

122A06′01″

CARQ (s, p) 38A02′35″ 17.5 m

122A10′31″

CUT (nb, s, p, o) 38A05′24″ 8.3 m

122A00′20″

GARN (s) 38A05′44″ 6.1 m

122A01′32″

GARNW (v, s, p, o) 38A06′23″ 2.4 m

122A02′53″

GC (v, s, p, o) 38A07′12″ 1.4 m

122A01′34″

GDOL (v, s, p, o) 38A07′01″ 1.7 m

122A02′26″

GS (v, s, p, o) 38A06′28″ 1.2 m

122A01′22″

HC (v, s, p, o) 38A04′26″ 0.9 m

121A55′45″

HDOL (v, s, p, o) 38A04′25″ 1.9 m

121A57′27″

HS (v, s, p, o) 38A03′28″ 1.1 m

121A55′59″

MAL (bb, s, p) 38A02′33″ 16.4 m

121A54′59″

MART (s, p) 38A01′40″ 8.0 m

122A08′22″

MET 38A03′10″ na

121A56′10″

+2.1 m, +10.0 m, and +17.7 m 5/20/95 (140) – 10/31/95 (304)

+5.5 m and +11.5 m 6/01/95 (152) – 10/23/9 5(296)

+9.3 m and +17.0 m 6/05/95 (156) – 11/01/95 (305)

+3.1 m and +7.5 m 7/07/95 (188) – 10/23/95 (296)

+1.4 m and +5.3 m 7/05/95 (186) – 10/22/95 (295)

+1.8 m (v) and +1.7 m 9/18/95 (261) – 10/23/95 (296)

+0.8 m (v) and +0.7 m 7/04/95 (185) – 8/18/95 (230)

+1.1 m (v) and +1.0 m 7/06/95 (187) – 9/18/95 (261)

+0.6 m (v) and +0.5 m 7/06/95 (187) – 9/18/95 (261)

+0.3 m (v) and +0.2 m 7/09/95 (190) – 10/24/95 (297)

+1.5 m (v) and +1.5 m 7/06/95 (187) – 9/18/95 (261)

+0.5 m (v) and +0.4 m 7/07/95 (188) – 9/18/95 (261)

+15.4 m 5/30/95 (150) – 10/27/95 (300)

+1.0 m and +7.5 m 7/06/95 (187) – 11/16/95 (320)

na 11/01/95 (305) 5/01/95 (121) –

4 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

Table 1. Data-collection instrument locations and deployment periods—Continued

Depth Sensor Deployment Station Name Position (MLLW In depth period

meters) (meters) (Julian Days)

MID (bb, s, p) 38A03′42″ 8.5 m

122A00′03″

MOTH (v, s, p, o) 38A05′29″ 8.9 m

122A04′30″

RYER (s) 38A04′45″ 6.2 m

122A02′11″

RYERE (nb, s, p) 38A04′28″ 5.3 m

122A01′16″

SPOON (v, s, p, o) 38A04′15″ 2.4 m

121A54′42″

WICK (s) 38A03′30″ 15.3 m

122A14′24″

+0.8 m and +7.7 m 10/23/95 (296) 6/01/95 (152) –

+8.3 m (v) and +8.2 m 9/18/95 (261) – 10/23/95 (296)

+5.4 m 7/07/95 (188) – 8/18/95 (230)

+4.5 m 6/01/95 (152) – 8/18/95 (230)

+1.5 m (v) and +1.6 m 9/18/95 (261) – 10/24/95 (297)

+0.3 m and +12.6 m 4/30/95 (120) – 10/31/95 (304)

Table 2. Specifications for instruments used in Suisun Bay, California [Salinities in this report are presented in practical salinity units, which is a conductivity ratio; therefore, it has no physical units (Millero, 1993); AC, degrees Celsius; m, meter; mS/cm, millisiemens per centimeter at 25AC; mm, millimdter; dbar, decibar; cm/s, centimeters per second; FS, full scale; CT, conductivity-temperature; CTD, conductivity-temperature-depth sensor; OBS, optical backscatternce sensor; ADCP, acoustic Doppler current profiler; FTU, formazin turbidity unit]

Range Accuracy Resolution

Seabird: Seacat CT

Temperature −5–35ºC +/- 0.01 +/- 0.001

Conductivity 0–70 mS/cm +/- 0.001 +/- 0.0001 Ocean Sensors: Os200 CTD

Temperature −2– 35ºC 0.01 percent FS 0.001 percent FS

Conductivity 0.5–65 mS/cm 0.02 percent FS 0.001 percent

Salinity 1–45 0.03 percent FS 0.001 percent

Pressure 0–50 dbar 0.50 percent FS 0.005 percent D & A: Optical Backscatterance Sensor (OBS-3)

Turbidity 0.02–2,000 FTU 2.0 percent FS 0.001 FTU Interocean Systems: S4 Current Meter

Current Speed 0–350 cm/s 2.0 percent FS 0.2 cm/s

Direction 0–360 degrees +/- 2 degrees 0.5 degrees

Pressure 0–70 m +/- 0.15 percent 4 mm EG & G: Velocity Meter

Temperature −2–35ºC 0.05ºC 0.01ºC

Pressure 0–999.9 dbar 0.5 percent 0.2 dbar

Velocity 0–360 cm/s 3 percent 0.1 cm/s

Heading 0–360 degrees +/- 5.0 degrees 1.0 degrees RD Instruments ADCP: Broad Band and Narrow Band

Velocity +/- 1,000 cm/s < 1 cm/s 0.1 cm/s

Heading 0–360 degrees 2 degrees 02 degrees

Introduction 5

----------

The data in this report are organized by location (fig. 2) and primarily presented as time-series plots. Harmonic analysis results characterize the tidal motions, and low-pass-filtered data characterize the residual (tidally averaged) motions. Additional characteristics of the tidal velocities, such as the root-mean-square (RMS) speed, tidal form number, principal current direction, and spring-tide maximum and neap-tide minimum velocities also are presented.

Study Area

Geographic Setting

Suisun Bay is roughly 25 kilometers (km) long, has a surface area of approximately 94 square kilometers (km2), a mean depth of 4.3 meters (m), and bottom topography characterized by a network of deep channels separated by a series of islands. The channels are bounded to the north and east by two large shallow regions, known as Grizzly and Honker Bays (fig. 2), that are thought to play an important role in maintaining salinities throughout the northern reach during late summer through early winter (Fischer, 1976).

Tides

Because of its complex bathymetry and brackish water, the hydrodynamics of Suisun Bay are among the most complicated in San Francisco Bay (Walters and Gartner, 1985). The tides propagate through the channels of Suisun Bay as progressive waves where the water level and tidal currents are roughly in phase. For example, at Station BULLS (fig. 2), the currents lead the phase of the water level by about 10 minutes (harmonic analysis results, appen. C). That is, the currents reach their peak ebb/ flood magnitudes roughly 10 minutes before low/high water, respectively. The currents leading the water level are typical of frictionally dominated systems such as San Francisco Bay (Officer, 1976). However, the tidal signal in the vicinity of the shallows of Grizzly and Honker Bays is more like a standing wave, due to friction and shoreline reflection (Burau and Cheng, 1988). In a pure standing wave, the water level and currents are 90 degrees out of phase. One expects standing wave behavior when the resonant frequency of an enclosed basin closely approximates the frequency of the tidal forcing. The resonant period of Grizzly and Honker Bays are on the order of Tres ~ 1 hour, where the resonant period,

4LTres ∼

gH - ,

is estimated by a quarter wave resonator ( g ~9.81m/s2 is gravity and H is depth; H is taken to be ~1.5 m, L is the length of the basin, which, for Grizzly and Honker Bays is taken to be L ~4 km) (Pond and Pickard, 1983). Because the resonant periods for Grizzly and Honker Bays are much shorter (~1 hour) than the period of the tidal forcing (~12 hours), one expects only partial standing wave behavior in these small sub-bays. This is confirmed at Station GC (fig. 2) where the water level and currents are approximately 35 degrees out of phase (harmonic analysis results, appen. I). The phase relation between the water level and currents is important in the transport of salt, sediment, and biota in tidally dominated systems. Stokes drift is an upstream residual current that can occur in progressive wave systems like San Francisco Bay’s northern reach (Burau and others, 1998). Stokes drift, which can be large when the water level and tidal currents are roughly in phase, can contribute significantly to transport into and out of shallow regions, such as Grizzly and Honker Bays, because the tidal range is a significant fraction of the mean depth.

6 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

S

Figuothe

Currents

Owing to Suisun Bay’s complex bathymetry, the timing, magnitude, and direction of the tidal currents vary significantly throughout Suisun Bay. An example of the spatial variability of the currents generated by a numerical model is shown in figure 3. The magnitude of tidal currents usually vary in direct proportion to the water depth (slower in the shoals); orientation is generally directed parallel to the prevailing bathymetry contours (Cheng and Gartner, 1984b). The tidal currents in the channels are on the order of 100 centimeters per second (cm/s) whereas the tidal currents in the shallows are on the order of 50 cm/s or less.

As compared to the tidal currents, the residual (tidally averaged) currents usually are an order of magnitude smaller (for example, ~10 cm/s in the channels). These residual currents are affected by Delta outflow (hydrology) and atmospheric forcing (meteorological). At times, these factors have a significant influence on the residual circulation patterns (Walters and Gartner, 1985). Therefore, the hydrologic and meteorological conditions during the study period are discussed in the following sections.

Hydrologic Conditions

The Sacramento–San Joaquin Delta provides most of the freshwater that flows into Suisun Bay (Jassby and others, 1995). In winter and spring, this freshwater input can significantly alter the tidal and residual circulation in Suisun Bay. For example, the residual currents that are typically on the order of 10 cm/s during summer can increase to more than 60 cm/s from the influx of freshwater during uncontrolled runoff events in winter. Moreover, freshwater flows in winter or early spring can advect salt seaward of Suisun Bay, effectively removing density-driven circulation from this area during these events.

Eastern Suisun Bay tidal velocities

Velocity Scale - 1 meter per second 0, 2-meter depth contours shown

N

Honker Bay

Ryer Island

Grizzly Bay

chematic not to scale

re 3. Numerical model simulation of depth-averaged tidal current velocities in Suisun Bay, California, during ebb current (Cheng and rs, 1993).

Introduction 7

Compared to the 1993 and 1994 water years, the 1995 water year was characterized by high flows with three distinct discharge peaks in excess of 5,000 cubic meters per second (m3/s) (fig. 4). The relatively high Delta outflows “pushed” salinity seaward of Suisun Bay beginning about Julian day 70. Salinity returned to the western part of Suisun Bay at Bulls Head around Julian day 145. Figure 4D provides a detailed time series of the Delta outflow that entered Suisun Bay during the study period. This record shows the effect on Delta outflow caused by the gate failure at Folsom Dam on the American River.

12000

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DAYS FROM JANUARY 1

D

Flow resulting from Folsom Dam� gate failure

110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340

DAYS FROM JANUARY 1, 1995

Figure 4. Delta outflow (DAYFLOW) estimates (California Department of Water Resources, 1986) for A, 1995; B, 1994; C, 1993; and D, during the time when instruments were deployed in Suisun Bay, California.

8 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

Meteorological Conditions

Changes in meteorology also can affect the hydrodynamics of Suisun Bay through changes in atmospheric pressure and wind. For example, atmospheric pressure can create residual currents in Suisun Bay by significantly raising or lowering sea level (Walters and Gartner, 1985). Figure 5 shows barometric pressure, wind direction, wind speed, air temperature, and visible light measured during the study at Station Channel Marker 27 in Suisun Bay (fig. 2). Based on data shown in figure 5, the

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0 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340

E

DAYS FROM JANUARY 1, 1995

Figure 5. A, barometric pressure; B, wind direction; C, wind speed; D, air temperature; and E, visible light at Station Channel Marker 27 in Suisun Bay, California, May 12, 1995, through November 6, 1995. By convention, wind direction is reported as the direction the wind is coming from (for example, westerly winds have a direction of 270 degrees).

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Introduction 9

meteorological conditions during the 1995 study were characterized by relatively constant barometric pressures and intermittent westerly winds that varied from 0–10 meters per second (m/s). Wind stress on the water surface can produce a current that flows in the direction of the wind at the surface and flows opposite the wind direction at depth in the channels (Fischer and others, 1979; Hunter and Hearn, 1987). Wind direction is reported as the direction from which the wind is coming (westerly winds have a direction of 270 degrees). Winds in Suisun Bay are characterized by prevailing westerly and southwesterly winds in late spring, summer, and early autumn and by more intermittent southerly winds in winter (Gartner and Cheng, 1983).

Sediment

Sediments are an important component of the San Francisco Bay estuarine system. Bottom sediments provide habitat for benthic organisms and are a reservoir of nutrients that contribute to the maintenance of estuarine productivity (Hammond and others, 1985). Potentially toxic substances, such as metals and pesticides, adsorb to sediment particles (Kuwabara and others, 1989; Domagalski and Kuivila, 1993; Flegal and others, 1996). Benthic organisms can ingest these substances and introduce them into the food web (Luoma and others, 1985; Brown and Luoma, 1995; Luoma, 1996).

The transport and fate of suspended sediments are important factors in determining the transport and fate of constituents adsorbed on the sediments. In Suisun Bay, the maximum concentration of suspended sediment usually marks the position of the turbidity maximum, which is a crucial ecological region in which suspended sediments, nutrients, phytoplankton, zooplankton, larvae, and juvenile fish accumulate (Peterson and others, 1975; Arthur and Ball, 1979; Kimmerer, 1992; Jassby and Powell, 1994; Schoellhamer and Burau, 1998; Schoellhamer 2001).

Suspended sediments limit the availability of light in San Francisco Bay, which, in turn, limits photosynthesis and primary photosynthetic carbon production (Cole and Cloern, 1987; Cloern, 1987, 1996). Suspended sediments also deposit in ports and shipping channels, which then must be dredged to maintain navigation (U.S. Environmental Protection Agency, 1992). Large tidal velocities, spring tides, and wind waves in shallow water all are capable of resuspending bottom sediments (Powell and others, 1989; Schoellhamer, 1996).

Discharge from the Delta contains 83–86 percent of the fluvial sediments that enter San Francisco Bay (Porterfield, 1980). Bottom sediments in Suisun Bay are composed mostly of silts and clays in shallow water and silts and sands in deeper water (Conomos and Peterson, 1977). An annual cycle of deposition and resuspension begins with large influx of sediment during winter, primarily from the Central Valley (Goodwin and Denton, 1991; Oltmann and others, 1999). Much of this new sediment deposits in San Pablo and Suisun Bays. Stronger westerly winds during spring and summer cause wind-wave resuspension of bottom sediment in these shallow waters and increase SSC (Ruhl and Schoellhamer, 1999). The ability of wind to increase SSC is greatest early in the spring, when unconsolidated fine sediments easily can be resuspended. As the fine sediments are winnowed from the bed, however, the remaining sediments become progressively coarser and less erodible (Conomos and Peterson, 1977; Krone, 1979; Nichols and Thompson, 1985; Ruhl and Schoellhamer, 1999).

Acknowledgments

The authors greatly appreciate the help of Randall Brown (DWR) and Kenneth Lentz (USBR) for arranging the IEP funding for this work. The U.S. Department of Interior’s Placed Based Program provided funding for the sediment-transport component of this study and for most of the equipment used in this study. Catherine Ruhl provided the suspended-solids concentration and associated calibration plots. The authors gratefully acknowledge Paul Buchanan, Jim DeRose, Jeff Gartner, Brian McGeehan,

10 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

Robert Sheipline, and Brad Sullivan of the USGS, and Mark Stacy of Stanford University for their assistance deploying, servicing, and recovering field instruments used in this study.

FINDINGS

This report describes and documents hydrodynamic and SSC data collected in Suisun Bay from May 30 through October 27, 1995. In this section, we discuss the general spatial and temporal patterns observed in the hydrodynamic data organized by timescale, beginning with the tidal timescale and followed by the residual, or tidally averaged, timescale. The tidal and residual timescale sections include discussions on current and salinity characteristics. In addition, findings derived from the SSC data are summarized.

Tidal Timescale Variability

Currents

The tidal currents often are best characterized using results from harmonic analysis. Harmonic analysis summary sheets are provided in the appendices for sea-level and tidal-current data. The spatial variability in the tidal currents are summarized in figures 6 and 7 as the spring tidal current maximum and neap tidal current minimum in vector form and the RMS current speed, numerically. Figure 6 shows the near-surface tidal currents in the channels measured using ADCPs and figure 7 shows the currents in the shallows using single-point velocity measurements. The directions of the current vectors in these figures are oriented using the principal direction of the tidal current ellipse at each location. The principal direction for each station is determined from harmonic analysis and presented in the appendices.

Figure 6 shows that the tidal currents dissipate as the tide wave propagates landward through Suisun Bay; the RMS currents are roughly 70 cm/s on Suisun Bay’s western boundary compared to 60 cm/s on its eastern boundary at Mallard Island. Moreover, the RMS tidal currents are significantly less through the northern channels (~50 cm/s). Based on harmonic analysis, the magnitude of spring tidal currents are roughly twice those of the neap tidal currents. Finally, the tidal currents in the shallows are significantly less than in the channels (compare figs. 6 and 7). The tidal current ellipses in shallow regions also are less eccentric than those in channels because the currents in the shallows are less bathymetrically constrained (compare the major and minor axes of the tidal current ellipses to the harmonic analysis results for velocity in the appendices).

Salinity

Salinities and salinity stratification in Suisun Bay vary significantly at tidal timescales, as shown in a typical example from Suisun Cutoff, Station CUT (fig. 8). (Salinities reported here are according to the practical salinity scale and, therefore, have no units. However, sea water, which contains about 35 parts per thousand dissolved solids, is represented by 35 on the practical salinity scale.) In this example, near-bed salinities vary from 2.5 to 7 throughout the tidal cycle and salinity stratification changes from vertically well mixed (no top-to-bottom salinity difference) to significantly stratified with top-to-bottom differences on the order of 2. In advection-dominated systems such as Suisun Bay, the tidal timescale salinity variations principally are a result of the strong tidal currents and a persistent, though seasonally variable, horizontal salinity gradient typically on the order of 0.5 km-1. In this example, salinities vary by roughly 5 throughout the tidal cycle, however the degree to which salinities vary over a tidal cycle can change depending on the strength of the horizontal salinity gradient, which itself varies at tidal, fortnightly, and seasonal timescales. For example, large changes in salinity at a fixed site are expected when the horizontal salinity gradient is locally large. Moreover, because advection dominates salt transport, salinities reach their peak at high water slack, and are lowest during low water

Findings 11

slack, as is shown in figure 8. Finally, salinity stratification in the low salinity zone (0–10) usually is greatest during flood tides and least during ebb tides (fig. 8).

Residual Timescale Variability

Currents

As a typical example of velocity profiles measured in the ship channel of Suisun Bay (fig. 1), time-series of the longitudinal and transverse residual currents at Station BULLS (fig. 2) are presented in figure 9. The large vertical shears in figure 9, especially at sections A and B, show that the velocity profiles at Station BULLS are clearly affected by the presence of salinity. The example profiles given in figure 10 do not resemble a log profile typical of water surface slope-driven flows, nor do they resemble the residual current profiles typical of gravitational circulation (Hansen and Rattray, 1965). The shapes

Instrument position Spring tidal current maximum Neap tidal current minimum

2 1 0 1 Current speed, meters per second

N

41 cm/s

Honker Bay

60 cm/s

Mallard Island

RMS current speed

0 5 KILOMETERS

0 5 MILES

Figure 6. Near-surface tidal currents obtained from harmonic analysis of acoustic Doppler current profiler measurements in Suisun Bay, California, (the lengths of the vectors at each location corresponds to magnitude). The spring tidal current maximum is estimated by (M2 + S2) + (O1 + K1) and the neap tidal current minimum is not less than (M2 - S2) + (O1 - K1) where M2 and S2 are amplitudes of the principal lunar and solar semidiurnal partial tides, respectively, and O1 and K1 are amplitudes of the principal lunar and Luni-solar diurnal partial tides, respectively (Cheng and Gartner, 1984a). The number associated with each current vector is the root-mean-squared (RMS) current speed, in centimeters per second (cm/s).

Carquinez Strait Suisun Bay

51 cm/s

73 cm/s

74 cm/s

53 cm/s

Grizzly Bay

Ryer Island

12 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

Figureof the tidal ctides, r1984a)

of residual current profiles measured in Suisun Bay’s ship channel are, therefore, a combination of these two archetypes.

To show that the lack of upstream near-bed Eulerian residual currents was a consistent feature throughout Suisun Bay during this study, the tidally averaged bottom currents obtained from all of the ADCPs deployed during 1995 are shown in figure 11. Positive (flood-directed) near-bed currents are indicative of gravitational circulation, which was prevalent during this study in Carquinez Straits, represented by Station BEN (fig. 11B, BEN). The near-bed residual currents were, for the most part, directed seaward (negative) in Suisun Bay except for a few brief periods during neap tides in Suisun Cutoff (fig. 11C, CUT) and for a brief period (~10 days) at the end of the record at Station MID (which also occurred during a neap tide). Since the near-bed residual currents are, for the most part, directed seaward, the residual currents cannot contribute to upstream accumulations of suspended sediment and biota, as suggested in the classic conceptual model of estuarine turbidity maxima formation (ETM) offered by Authur and Ball (1979).

Instrument position

Spring tidal current maximum Neap tidal current minimum

0.5 0 Current speed, meters per second

N

10 cm/s RMS current speed

9 cm/s

Honker Bay

24 cm/s Mallard Island

0 5 KILOMETERS

0 5 MILES

7. Near-bed tidal currents obtained from harmonic analysis of single-point-velocity measurements in Suisun Bay, California, (the lengths vectors at each location corresponds to magnitude). The spring tidal current maximum is estimated by (M2 + S2) + (O1 + K1) and the neap urrent minimum is not less than (M2 - S2) + (O1 - K1) where M2 and S2 are amplitudes of the principal lunar and solar semidiurnal partial espectively, and O1 and K1 are amplitudes of the principal lunar and Luni-solar diurnal partial tides, respectively (Cheng and Gartner, . The number associated with each current vector is the root-mean-squared (RMS) current speed, in centimeters per second (cm/s).

Carquinez Strait

Suisun Bay

17 cm/s

17 cm/s

25 cm/s

Grizzly Bay

Ryer Island

Findings 13

Salinity

Subtidal salinity variability in Suisun Bay primarily depends on Delta outflow and density-driven circulation. Density-driven circulation depends on tide-induced vertical mixing which, in turn, varies with the spring/neap cycle.

Delta outflow accounts for most of the seasonal variability in salinity. During the large winter uncontrolled runoff events (fig. 4D) Suisun Bay can be completely fresh. At the other extreme, following

Minimum salinity� Maximum salinity�

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C

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at low water slack at high water slack

Low� water� slack

High� water� slack

Near-surface� Near-bed

Weaker� Stronger� stratification� stratification� on ebbs on floods

Figure 8. Time-series plot of A, salinity; B, depth-averaged, along-channel (axial) current speed; and C, vertical salinity stratification collected at Station CUT (fig. 2) in Suisun Bay, California. Salinities in this report are presented without units because salinity is a conductivity ratio function; therefore, it has no physical units (Millero, 1993).

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14 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

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Figure 9. Longitudinal and transverse residual currents at Station BULLS in Suisun Bay, California, June 1, 1995, through September 19, 1995. Tidal current speed at the velocity measurement location (BIN) 19 is shown in the top panel for reference. The velocity measurement at BIN 1 is located 1.9 meters off the bed. The remaining bins are evenly spaced towards the surface at 1.0-meter intervals (BIN 2 is at 2.9 meters, etc.). Principal direction is 65.0 degrees relative to true north. (A) and (B) are presented in figure 10.

Findings 15

300-30

6

�A) Julian Day 175, 1995

300-30 -6

6

0

B) Julian Day 240, 1995

TRANSVERSE� VELOCITY, IN�

CENTIMETERS� PER SECOND

ALONG-CHANNEL VELOCITY, IN CENTIMETERS PER SECOND

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ALONG-CHANNEL VELOCITY, IN CENTIMETERS PER SECOND

TRANSVERSE� VELOCITY, IN� CENTIMETERS� PER SECOND

NEAR SURFACE

NEAR BOTTOM

NEAR SURFACE

NEAR BOTTOM

0.5 METER INCREMENTS

0.5 METER INCREMENTS

�

�

Figure 10. Three-dimensional perspective view of residual current profiles measured by an acoustic Doppler current profiler (Station BULLS, fig. 2) in Suisun Bay, California, on (A), Julian day 175 and (B), Julian day 240. These profiles were taken at the vertical dashed lines shown in figure 9. The net residual currents are down estuary in the profiles shown (though weakly so near the bed); the shear in these profiles clearly show that these profiles, nonetheless, are affected strongly by the horizontal salinity gradient. Principal direction 75 degrees.

16 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

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1995 ADCP LOCATION

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Figure 11. Time-series plots of A, DAYFLOW (California Department of Water Resources, 1986) and the near-bed residual along-channel or axial currents at B, Stations BEN (solid) and BULLS (dash); C, Stations RYER (solid) and CUT (dash); and D, Stations MID (solid) and MAL (dash) Suisun Bay, California, May 30, 1995, through October 27, 1995. Positive axial current speed indicates a landward flow.

Findings 17

periods of prolonged low Delta outflows that typically occur in late fall and early winter, salinities in Suisun Bay can be relatively high (approximately 20 at Suisun Bay’s eastern end). During the study, at Station CUT, for example, the tidally filtered salinity (fig. 12D) varied inversely with Delta outflow (fig. 12A). Comparing figures 12A and 12D, one can see that as Delta outflows subsided from Julian day 200 to 235, tidally filtered salinities increased. Conversely, when Delta ouflow gradually increased from 300 to 700 m3/s beginning on day 230, salinities at Station CUT decreased. And finally, when outflows began to subside again near Julian day 270, salinities began to increase.

Weak neap tide 1.5

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E

D

C

B

A

x10 3 Weak neap tide Weak neap tide

DAYS FROM JANUARY 1

Near surface� Near bed

DAYS FROM JANUARY 1, 1995

Figure 12. Time-series plot of Station CUT (fig. 2), Suisun Bay, California; A, DAYFLOW (California Department of Water Resources, 1986); B, depth-averaged along-channel (axial) current speed; C, root-mean-squared (RMS) current speed; D, tidally averaged near-bed (solid) and near-surface (dash) salinity; and E, tidally filtered vertical salinity stratification. Salinities in this report are presented without units because salinity is a conductivity ratio; therefore, it has no physical units (Millero, 1993).

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18 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

At fortnightly timescales, salinity and salinity stratification varied significantly with the spring/ neap cycle. Spring tides are characterized by large tidal ranges and strong tidal currents, whereas neap tides have small tidal ranges and weak current speeds. The energy in the tidal currents can be quantified by the RMS current speed that is plotted in figure 12C. High RMS current speeds are associated with spring tides; low RMS current speeds with neap tides. As is shown in figure 12D, the tidally averaged salinities episodically peak at Station CUT during weak neap tides (for example, troughs in the RMS current speed). Moreover, during neap tides, when the tidally averaged salinity is increasing, dramatic spikes in salinity stratification also occur (fig. 12E). Although the magnitudes of variability in the tidally averaged salinity and salinity stratification vary from site to site, these basic trends are consistently observed throughout Suisun Bay.

Affect of Folsom Dam Spillway Gate Failure on Suisun Bay Hydrodynamics

Based on analysis of tidally averaged near-bed salinity and depth-averaged currents in the channels, the hydrodynamics of Suisun Bay were affected minimally by the Folsom Dam spillway gate failure (July 17, 1995; Julian day 198). The effect of gate failure is detectable only in Suisun Bay at the tidally averaged timescale. Even though the flows in the American River reached a peak discharge of roughly 1,000 m3/s as a result of the failure, this peak is relatively small [roughly 15 percent of the approximately 7,000 m3/s tidal flows that occur daily in the channels of Suisun Bay (Smith and others, 1995)] and the discharge from the failure likely was attenuated greatly when it reached Suisun Bay.

An increase in seaward (negative) flow at Mallard Island following the gate failure (fig. 13) possibly could be attributed to its occurrence. However, this increase is on the order of the longer-term natural variability in the residual currents at Mallard Island. At the stations seaward of Mallard Island [CUT (fig. 13C) and BULLS (fig. 13D)] the effect of the gate failure on the depth-averaged residual currents essentially is nonexistent. Moreover, the response of the tidally averaged near-bed salinities to the gate failure is indistinguishable from the natural variability (fig. 14). Salinity data from the eastern stations (CUT, MAL, and RYER) could not be used to assess the effect of the gate failure because these stations were completely fresh following the gate failure. Interestingly, the tidally averaged salinities at stations BULLS and MART increase slightly following the gate failure. If the gate failure had an effect, it would have lowered salinities in Suisun Bay by increasing the supply of freshwater into the eastern end of Suisun Bay. The increase in the tidally averaged near-bed salinities at these stations likely resulted from increased density driven circulation that occurred because of the neap tidal conditions during the time of the gate failure. Neap tides occur at the minima in the RMS depth-averaged current speed (fig. 14C).

Sediment Transport

The hydrodynamic and SSC data have been used to study sediment transport in Honker Bay and Spoonbill Creek, salt and sediment transport in Suisun Cutoff, and an estuarine turbidity maximum (ETM) between the Reserve Fleet Channel and Suisun Cutoff. These findings are summarized below.

Warner and others (1997) determined that Spoonbill Creek at the back of Honker Bay acts as a sediment transport pathway. Significant increases in suspended-solids flux (SSF) occurred during periods of sustained winds directed along the axis of Honker Bay (westerly winds). The wind induced surface shear stress increases SSF out of Honker Bay through Spoonbill Creek through the combination of two effects: (1) wind-wave resuspension of bed sediments elevates SSC within Honker Bay, and at the same time, (2) higher water level at the eastern end of Honker Bay relative to the Sacramento River creates a net barotropic pressure gradient across Spoonbill Creek which drives a residual advective SSF from Honker Bay through Spoonbill Creek into the Sacramento River. The residual dispersive flux was also out of Honker Bay into the Sacramento River because the tidal excursion in Spoonbill Creek

Findings 19

(approximately 4 km and approaches 6 km) is much longer than Spoonbill Creek itself (3 km). Therefore, high SSC water advected from Honker Bay into the Sacramento River through Spoonbill Creek on the ebb tide does not return on the following flood tide which creates the dispersive SSF. The total SSF was always out of Honker Bay during Fall 1995 suggesting that the relatively high metals and pesticide concentrations observed in Honker Bay are not advected through Spoonbill Creek into Honker Bay during this time of year.

1.5

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D

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A Folsom Dam Gate Failure

DAYS FROM JANUARY 1, 1995

Figure 13. Time-series plot of A, DAYFLOW (California Department of Water Resources, 1986); the tidally averaged, depth-averaged, along-channel (axial) current speed at B, Station MAL; C, Station CUT; and D, Station BULLS (fig. 2) in Suisun Bay, California. Vertical dashed line indicates time of Folsom Dam gate failure.

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20 Hydrodynamic and Suspended-Solids Concentration Measurements in Suisun Bay, California, 1995

Data from Suisun Cutoff shows that gravitational circulation transports salt and sediment differently (Schoellhamer and Burau, 1998). Landward pulses that develop along the bottom at the beginning of flood tides during weaker neap tides greatly increase the residual landward salt flux. SSC, however, is smallest during these neap tides and greatest during spring tides. During neap tides, when the landward pulses occur, relatively little suspended solids are available to be transported by the pulses. During spring tides, SSC is greater during floodtide than ebbtide, so the tidally-averaged flux of sediment is landward. Landward transport of sediment occurs during spring tides when gravitational circulation is weakest; thus, gravitational circulation does not necessarily cause "entrapment" in Suisun Bay.

Bottom topography enhances salinity stratification, gravitational circulation, and ETM formation seaward of sills (Jay and Musiak, 1994; Schoellhamer, 2001). The sill between the Reserve Fleet Channel and Suisun Cutoff supports the formation of an ETM (Schoellhamer, 2001). Two topographic features that place an upstream limit on gravitational circulation at the sill are a decrease in MLLW depth from 9–5 m in the landward direction at the sill and constriction of the channel in Suisun Cutoff (Burau

1.5

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40 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275

C

B

A Folsom Dam Gate Failure

MART� BULLS� MOTH

DAYS FROM JANUARY 1, 1995

Figure 14. Time-series plot of A, DAYFLOW (California Department of Water Resources, 1986); B, tidally averaged salinity at Stations BULLS (solid), MART (dash) and MOTH (dot); and C, root-mean-squared (RMS) depth-average current speed (fig. 2) in Suisun Bay, California. Vertical dashed line indicates time of gate failure. Salinities in this report are presented without units because salinity is a conductivity ratio; therefore, it has no physical units (Millero, 1993).

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Findings 21

and others, 1998). This topographic control traps particles in the Reserve Fleet Channel. Tidally averaged SSC always was greater in the Reserve Fleet Channel than in Suisun Cutoff as salinity returned to Suisun Bay in 1995.

SUMMARY

Hydrodynamic and suspended-solids concentration measurements were made by the U.S. Geological Survey in Suisun Bay, California, between May 30, 1995, and October 27, 1995. The data are presented in time-series form where the tidal timescale characteristics are reflected in raw data plots and in harmonic analysis results. The tidally averaged variations in the data are captured in plots of the low-pass filtered data. These data document a period of transition from a freshwater-inflow-dominated condition towards a quasi steady-state summer condition when density-driven circulation and tidal nonlinearities become relatively important as long-term transport mechanisms. Even though salinities increased overall in Suisun Bay during the study period, the near-bed residual currents were directed primarily seaward, indicating that salinity intrusion was accomplished in the absence of gravitational circulation.

During this study, the Folsom Dam spillway failed, allowing the analysis of the hydrodynamic effects in Suisun Bay. Based on the tidally averaged near-bed salinity and depth-averaged currents after the failure, the effect was essentially nonexistent and was indistinguishable from the natural variability.

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