Hydrodkynamic and Suspended-Solids Concentration Measurements ...

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 01-4086

Prepared in cooperation with the CALIFORNIA DEPARTMENT OF WATER RESOURCES and the

3021-14

U.S. BUREAU OF RECLAMATION

Sacramento, California

2001

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 Placer Hall, Suite 2012 6000 J Street Sacramento, CA 95819-6129

U.S. Geological Survey Information Services Box 25286 Federal Center Denver, CO 80225

CONTENTS Abstract ................................................................................................................................................................................. 1

Introduction .......................................................................................................................................................................... 1

Purpose and Scope ...................................................................................................................................................... 3

Study Area .................................................................................................................................................................. 6

Geographic Setting ........................................................................................................................................... 6

Tides ................................................................................................................................................................. 6

Currents ............................................................................................................................................................ 7

Hydrologic Conditions ..................................................................................................................................... 7

Meteorological Conditions ............................................................................................................................... 9

Sediment ............................................................................................................................................................ 10

Acknowledgments ...................................................................................................................................................... 10

Findings ................................................................................................................................................................................ 11

Tidal Timescale Variability ......................................................................................................................................... 11

Currents ............................................................................................................................................................ 11

Salinity .............................................................................................................................................................. 11

Residual Timescale Variability ................................................................................................................................... 12

Currents ............................................................................................................................................................ 12

Salinity .............................................................................................................................................................. 14

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

Sediment Transport...................................................................................................................................................... 19

Summary................................................................................................................................................................................ 22

References Cited ................................................................................................................................................................... 22

Appendix A: Data Reduction Details and Data Presentation ................................................................................................ 27

Data Reduction Details ............................................................................................................................................... 28

Acoustic Doppler Current Profiler Data ..................................................................................................................... 28

Sea-Level Data ............................................................................................................................................................ 28

Salinity Data ............................................................................................................................................................... 28

Conductivity-Temperature Sensors ............................................................................................................................. 29

Conductivity-Temperature-Depth-Optical Backscatterance Sensors ......................................................................... 29

Salinity Computation .................................................................................................................................................. 29

Suspended-Solids Concentration Computation ........................................................................................................... 31

File Formats ................................................................................................................................................................ 31

Time-Series File Format ............................................................................................................................................. 32

Acoustic Doppler Current Profiler File Format ........................................................................................................... 34

Data Presentation ........................................................................................................................................................ 35

Plotting of Oceanographic Data ................................................................................................................................. 36

Low-Pass Filter ........................................................................................................................................................... 36

Harmonic Analysis ..................................................................................................................................................... 36

Appendix B—Station BEN ................................................................................................................................................... 39

Appendix C—Station BULLS............................................................................................................................................... 51

Appendix D—Station CARQ ................................................................................................................................................ 63

Appendix E—Station MET .................................................................................................................................................. 69

Appendix F—Station CUT ................................................................................................................................................... 75

Appendix G—Station GARN................................................................................................................................................ 89

Appendix H—Station GARNW ............................................................................................................................................ 93

Appendix I—Station GC ....................................................................................................................................................... 101

Appendix J—Station GDOL ................................................................................................................................................. 109

Appendix K—Station GS ..................................................................................................................................................... 119

Contents

III

Appendix L—Station HC ..................................................................................................................................................... Appendix M—Station HDOL ............................................................................................................................................... Appendix N—Station HS ..................................................................................................................................................... Appendix O—Station MAL ................................................................................................................................................. Appendix P—Station MART ............................................................................................................................................... Appendix Q—Station MID .................................................................................................................................................. Appendix R—Station MOTH ............................................................................................................................................... Appendix S—Station RYER ................................................................................................................................................ Appendix T—Station RYERE .............................................................................................................................................. Appendix U—Station SPOON.............................................................................................................................................. Appendix V—Station WICK ................................................................................................................................................

127

135

145

153

163

171

187

195

199

209

217

FIGURES 1–3. Maps showing: 1. San Francisco Bay Estuary, California .......................................................................................................... 2

2. Data-collection locations and station names, Suisun Bay, California............................................................ 3

3. Numerical model simulation of depth-averaged tidal current velocities in Suisun Bay, California, during ebb current...................................................................................................................................................... 7

4,5. 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 ....................................................................................................... 12

7. Near-bed tidal currents obtained from harmonic analysis of point-velocity measurements in Suisun Bay, California ....................................................................................................................................................... 13

8–14. Graphs showing:

8. Time-series plot of A, salinity, B, depth-averaged along-channel (axial) current speed, and C, vertical

salinity 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-surface

salinity, 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........................................................................................................................... 32

A2. Example acoustic Doppler current profiler file format ........................................................................................ 34

B1. Diagram showing configuration of instrument deployment, Station BEN, May 20 through

October 31, 1995, Suisun Bay, California ........................................................................................................... 40

B2–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,


B7. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station BEN, May 20 through


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


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


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


B11. Residual currents, Station BEN, May 20 through October 31, 1995, Suisun Bay, California....................... 47

C1. Diagram showing configuration of instrument deployment, Station BULLS, June 1 through October 23, 1995,

Suisun Bay, California ......................................................................................................................................... 52

C2–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


C5. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station BULLS, June 1


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................ 59

D1. Diagram showing configuration of instrument deployment, Station CARQ, June 5 through

November 1, 1995, Suisun Bay, California ......................................................................................................... 64

D2–D9. Graphs showing:

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


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 .................... 70

E2. 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 ........................................................ 70

E3. 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 ............................. 71

E4. 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


L3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HC, July 28


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


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

L6. Longitudinal and transverse residual currents, Station HC, July 9 through October 24, 1995,


L7. Residual currents, Station HC, July 9 through October 24, 1995, Suisun Bay, California............................ 132

L8. Calibration curve for near-bottom optical backscatterance sensor, Station HC, July 28 through


M1. Diagram showing configuration of instrument deployment, Station HDOL, July 6 through September 18, 1995,


M2–M10. Graphs showing:

M2. Time-series plots of A, depth; B, temperature; and C, salinity, Station HDOL, July 6 through


M3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HDOL, July 6


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


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


M6. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station HDOL, April 30 through

November 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,


M9. Residual currents, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California.................. 141

M10. Burst velocity variance, Station HDOL, July 6 through September 18, 1995, Suisun Bay, California......... 141

M11. Calibration curve for near-bottom optical backscatterance sensor, Station HDOL, July 6 through


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


N2–N8. Graphs showing:

N2. Time-series plots of A, depth; B, temperature; and C, salinity, Station HS, August 1 through


N3. Time-series plots of low-pass-filtered A, depth; B, temperature; and C, salinity, Station HS, August 1


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


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,


N7. Residual currents, Station HS, July 7 through September 18, 1995, Suisun Bay, California........................ 150

N8. Calibration curve for near-bottom optical backscatterance sensor, Station HS, August 1 through


O1. Diagram showing configuration of instrument deployment, Station MAL, July 6 through November 16, 1995,


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


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


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


R7. Residual currents, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ......... 192

R8. Calibration curve for near-bottom optical backscatterance sensor, Station MOTH, September 18


S1. Diagram showing configuration of instrument deployment, Station RYER, July 7 through August 18, 1995,


S2,S3. Graphs showing:

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


S3. Time-series plots of low-pass-filtered A, temperature; and B, salinity, Station RYER, July 7 through


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


T3. 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 ............................................................................ 202

T4. Time-series plots of tidal currents, Station RYERE, June 1 through August 18, 1995, Bin 1

near-bottom bin, Suisun Bay, California........................................................................................................ 203

T5. Time-series plots of tidal currents, Station RYERE, June 1 through August 18, 1995, Bin 4

near-surface bin, Suisun Bay, California........................................................................................................ 203

T6. Longitudinal and transverse residual currents, Station RYERE, June 1 through August 18, 1995,


T7. 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


U3. 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 ................................................................. 212

U4. Time-series plot of suspended-solids concentration at Station SPOON, September 18 through


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


U6. Longitudinal and transverse residual currents, Station SPOON, September 18 through


U7. Residual currents, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California........ 214

U8. Calibration curve for near-bottom optical backscatterance sensor, Station SPOON, September 18


V1. 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


V3. 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. 2. A1. B1. B2. B3. C1. C2. C3. D1. F1. F2. F3. H1. H2. I1. I2. J1. J2. K1. K2. L1. L2. M1. M2. N1.

Data-collection instrument locations and deployment periods............................................................................... 4

Specifications for instruments used in Suisun Bay, California............................................................................... 5

Principal astronomical tidal frequencies, Suisun Bay, California .......................................................................... 38

Harmonic analysis results from depth measurements, Station BEN, June 1 through October 31, 1995,

Suisun Bay, California ............................................................................................................................................ 48

Harmonic analysis results for velocity, Station BEN, May 20 through October 31, 1995, Bin 1

near-bottom bin, Suisun Bay, California ................................................................................................................ 49

Harmonic analysis results for velocity, Station BEN, May 20 through October 31, 1995, Bin 9

near-surface bin, Suisun Bay, California ................................................................................................................ 50

Harmonic analysis results from depth measurements, Station BULLS, June 1 through October 23, 1995,


Harmonic analysis results for velocity, Station BULLS, June 1 through September 19, 1995, Bin 1


Harmonic analysis results for velocity, Station BULLS, June 1 through September 19, 1995, Bin 19


Harmonic analysis results from depth measurements, Station CARQ, June 5 through November 1, 1995,


Harmonic analysis results from depth measurements, Station CUT, July 7 through October 23, 1995,


Harmonic analysis results for velocity, Station CUT, May 31 through October 23, 1995, Bin 1


Harmonic analysis results for velocity, Station CUT, May 31 through October 23, 1995, Bin 6


Harmonic analysis results from depth measurements, Station GARNW, September 18 through

October 23, 1995, Suisun Bay, California .............................................................................................................. 100

Harmonic analysis results for velocity, Station GARNW, September 18 through October 23, 1995,


Harmonic analysis results from depth measurements, Station GC, July 4 through August 18, 1995,


Harmonic analysis results for velocity, Station GC, July 4 through August 18, 1995, Suisun Bay, California ..... 108

Harmonic analysis results from depth measurements, Station GDOL, July 17 through September 18, 1995, Suisun Bay, California ............................................................................................................................................ 117

Harmonic analysis results for velocity, Station GDOL, July 6 through September 18, 1995,


Harmonic analysis results from depth measurements, Station GS, July 6 through September 18, 1995,


Harmonic analysis results for velocity, Station GS, July 6 through September 18, 1995,


Harmonic analysis results from depth measurements, Station HC, July 28 through October 24, 1995,


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

Harmonic analysis results from depth measurements, Station HDOL, July 6 through September 18, 1995,


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

California ................................................................................................................................................................ 143

Harmonic analysis results from depth measurements, Station HS, August 1 through September 18, 1995,


Contents

XI

N2. Harmonic analysis results for velocity, Station HS, July 7 through September 18, 1995, Suisun Bay, California ................................................................................................................................................................ O1. Harmonic analysis results from sea-level measurements, Station MAL, May 8 through October 15, 1995, Suisun Bay, California ............................................................................................................................................ O2. Harmonic analysis results for velocity, Station MAL, July 6 through November 16, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... O3. Harmonic analysis results for velocity, Station MAL, July 6 through November 16, 1995, Bin 19 near-surface bin, Suisun Bay, California ................................................................................................................ P1. Harmonic analysis results from sea-level measurements, Station MART, May 1 through November 1, 1995, Suisun Bay, California ............................................................................................................................................ Q1. Harmonic analysis results from depth measurements, Station MID, June 1 through October 23, 1995, Suisun Bay, California ............................................................................................................................................ Q2. Harmonic analysis results for velocity, Station MID, June 1 through August 10, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... Q3. Harmonic analysis results for velocity, Station MID, June 1 through August 10, 1995, Bin 19 near-surface bin, Suisun Bay, California ..................................................................................................................................... Q4. Harmonic analysis results for velocity, Station MID, August 10 through October 23, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... Q5. Harmonic analysis results for velocity, Station MID, August 10 through October 23, 1995, Bin 7 near-surface bin, Suisun Bay, California ..................................................................................................................................... R1. Harmonic analysis results from depth measurements, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California .................................................................................................................................. R2. Harmonic analysis results for velocity, Station MOTH, September 18 through October 23, 1995, Suisun Bay, California ................................................................................................................................................................ T1. Harmonic analysis results from depth measurements, Station RYERE, June 27 through August 18, 1995, Suisun Bay, California ............................................................................................................................................ T2. Harmonic analysis results for velocity, Station RYERE, June 1 through August 18, 1995, Bin 1 near-bottom bin, Suisun Bay, California ..................................................................................................................................... T3. Harmonic analysis results for velocity, Station RYERE, June 1 through August 18, 1995, Bin 4 near-surface bin, Suisun Bay, California ..................................................................................................................................... U1. Harmonic analysis results from depth measurements, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California .............................................................................................................. U2. Harmonic analysis results for velocity measurements, Station SPOON, September 18 through October 24, 1995, Suisun Bay, California .............................................................................................................. V1. Harmonic analysis results from sea-level measurements, Station WICK, April 30 through October 31, 1995, Suisun Bay, California ............................................................................................................................................ CONVERSION FACTORS, ABBREVIATIONS, ACRONYMS, DATA-COLLECTION STATIONS, SYMBOLS, AND JULIAN DATE CALENDAR Multiply

centimeter (cm) centimeter per second (cm/s) cubic meter per second (m3/s) decibar (dbar) kilometer (km) square kilometer (km2) meter (m) meter per second (m/s) meter per second squared (m/s2) millibar (mbar) millimeter (mm) square meter (m2)

By

0.3937 0.3937 35.31 1.0197 0.6214 0.3861 3.281 3.281 3.281 0.0145 0.03937 10.76

To obtain

inch inch per second cubic foot per second meters of water (at 4°C) mile square mile foot foot per second foot per second squared pounds per square inch inch square foot

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

Contents

151 160 161 161 169 183 184 184 185 185 194 194 206 207 207 216 216 221

Abbreviations and Acronyms: deg, deg. C deg. T, E Hz kHz, mg/L mS/CM, mS/cm, mmhos/cm, Hm HS/cm ppt, cfs, cms, ADCP, BIN, CT, CTD, CTDO, DAYFLOW, DWR, ETM, EZ, FTU, IEP, MLLW, OBS RDI RMS, SC, SI SSC SSF UNESCO USBR, USGS,

degrees degrees Celcius degrees true equilibrium argument hertz kilohertz milligram per liter millisiemens per centimeter millimhos per centimeter micrometer microsiemens per centimeter parts per thousand cubic feet per second cubic meter per second Acoustic Doppler Current Profiler a depth cell from an ADCP conductivity-temperature conductivity-temperature-depth conductivity-temperature-depth-optical backscatter California Department of Water Resources delta outflow California Department of Water Resources estuarine turbidity maximum entrapment zone formazine turbidity unit Interagency Ecological Program for the San Francisco Bay Estuary mean lower low water optical backscatteranced sensor R.D. Instruments, Inc. root-mean-squared specific conductance (System International) International System of Weights and Measures suspended-solids concentration suspended-solids flux United Nations Educational, Scientific, and Cultural Organization U.S. Bureau of Reclamation U.S. Geological Survey

Data-collection stations: BEN

BULLS

CARQ

MET

CUT

GARN

GARNW

GC

GDOL

GS

HC

HDOL

HS

MAL

MART

MID

MOTH

RYER

RYERE

SPOON

WICK

Tidal symbols: J1

K1

K2

L2

M1

M2

M4

Mk3

Mu2

H2

m2

N2

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

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

5

-26

5

36

64

95

125

156

186

217

248

278

309

339

5

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

10

-21

10

41

69

100

130

161

191

222

253

283

314

344

10

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

15

-16

15

46

74

105

135

166

196

227

258

288

319

349

15

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

20

-11

20

51

79

110

140

171

201

232

263

293

324

354

20

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

25

-6

25

56

84

115

145

176

206

237

268

298

329

359

25

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

30

-1

30

89

120

150

181

211

242

273

303

334

364

30

31

90

212

243

365

31

31

151

304

Contents

XV

Julian Date Calendar—Continued For leap years Day

Dec

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

5

-26

5

36

65

96

126

157

187

218

249

279

310

340

5

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

10

-21

10

41

70

101

131

162

192

223

254

284

315

345

10

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

15

-16

15

46

75

106

136

167

197

228

259

289

320

350

15

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

20

-11

20

51

80

111

141

172

202

233

264

294

325

355

20

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

25

-6

25

56

85

116

146

177

207

238

269

299

330

360

25

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

30

-1

30

90

121

151

182

212

243

274

304

335

365

30

31

91

213

244

366

31

31

XVI

Jan

Contents

152

305

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 timeseries 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 nearbed 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

122 o00'

122 o30'

a m zu te on M

r ve Ri

Su isu nS lou gh

pa Na

ou Sl

Suisun Cut

Benicia Bridge

38o 00'

Fl ee

tC ha nn el

Carqu inez S trait

R es er ve

SAN PABLO BAY

gh

Grizzly Bay

Honker Bay

Ship Channel

SUISUN BAY

Mallard Island

Sa n

Pa bl o

St ra it

Martinez

AL NTR T

CE

AS

CO

Sacramento–San Joaquin River Delta

CA

Oc

EY LL S VA E NG RA n ea

ic cif Pa

CENTRAL BAY

LI

FO

RN

IA

Oakland

Golden Gate Bridge

Bay Bridge San Francisco

DEPTH MORE THAN 2.5 METERS

SOUTH BAY San Francisco International Airport

San Mateo Bridge

Dumbarton Bridge

37 o30' 0 0

5

10 KILOMETERS 5

10 MILES

SAN JOSE

Figure 1. San Francisco Bay Estuary, California.

2

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

Spoonbill Creek

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

o

121 53'

122 15' Instrument Descriptions

o

38 10'

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

N GDOL

Site Location

GC

Suisun Bay GS

DEPTH MORE THAN 2.5 METERS

Grizzly Bay GARNW

0

5 KILOMETERS

tb

GARN

HDOL

5 MILES

0

MOTH CUT

t

b HC

BULLS

BEN

tb

SPOON

Honker Bay

t

Chipps I. Benicia RYER

38 o 02'

WICK

b

HS MID

tb

CARQ

t

b

Martinez MART

t

RYERE

b

tb

MAL

t

MET

b

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

3

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]

Station Name

BEN (nb, s, p)

Position

38A02′37″

Depth (MLLW In meters)

Sensor depth (meters)

18.6 m

+2.1 m, +10.0 m, and +17.7 m

5/20/95 (140) – 10/31/95 (304)

12.3 m

+5.5 m and +11.5 m

6/01/95 (152) – 10/23/9 5(296)

17.5 m

+9.3 m and +17.0 m

6/05/95 (156) – 11/01/95 (305)

8.3 m

+3.1 m and +7.5 m

7/07/95 (188) – 10/23/95 (296)

6.1 m

+1.4 m and +5.3 m

7/05/95 (186) – 10/22/95 (295)

2.4 m

+1.8 m (v) and +1.7 m

9/18/95 (261) – 10/23/95 (296)

1.4 m

+0.8 m (v) and +0.7 m

7/04/95 (185) – 8/18/95 (230)

1.7 m

+1.1 m (v) and +1.0 m

7/06/95 (187) – 9/18/95 (261)

1.2 m

+0.6 m (v) and +0.5 m

7/06/95 (187) – 9/18/95 (261)

0.9 m

+0.3 m (v) and +0.2 m

7/09/95 (190) – 10/24/95 (297)

1.9 m

+1.5 m (v) and +1.5 m

7/06/95 (187) – 9/18/95 (261)

1.1 m

+0.5 m (v) and +0.4 m

7/07/95 (188) – 9/18/95 (261)

16.4 m

+15.4 m

5/30/95 (150) – 10/27/95 (300)

8.0 m

+1.0 m and +7.5 m

7/06/95 (187) – 11/16/95 (320)

na

na

5/01/95 (121) – 11/01/95 (305)

122A07′25″ BULLS (bb, s, p)

38A02′54″ 122A06′01″

CARQ (s, p)

38A02′35″ 122A10′31″

CUT (nb, s, p, o)

38A05′24″ 122A00′20″

GARN (s)

38A05′44″ 122A01′32″

GARNW (v, s, p, o)

38A06′23″ 122A02′53″

GC (v, s, p, o)

38A07′12″ 122A01′34″

GDOL (v, s, p, o)

38A07′01″ 122A02′26″

GS (v, s, p, o)

38A06′28″ 122A01′22″

HC (v, s, p, o)

38A04′26″ 121A55′45″

HDOL (v, s, p, o)

38A04′25″ 121A57′27″

HS (v, s, p, o)

38A03′28″ 121A55′59″

MAL (bb, s, p)

38A02′33″ 121A54′59″

MART (s, p)

38A01′40″ 122A08′22″

MET

38A03′10″ 121A56′10″

4

Deployment period (Julian Days)


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

Station Name

MID (bb, s, p)

Position

38A03′42″

Depth (MLLW In meters)

Sensor depth (meters)

8.5 m

+0.8 m and +7.7 m

6/01/95 (152) – 10/23/95 (296)

8.9 m

+8.3 m (v) and +8.2 m

9/18/95 (261) – 10/23/95 (296)

6.2 m

+5.4 m

7/07/95 (188) – 8/18/95 (230)

5.3 m

+4.5 m

6/01/95 (152) – 8/18/95 (230)

2.4 m

+1.5 m (v) and +1.6 m

9/18/95 (261) – 10/24/95 (297)

15.3 m

+0.3 m and +12.6 m

4/30/95 (120) – 10/31/95 (304)

122A00′03″ MOTH (v, s, p, o)

38A05′29″ 122A04′30″

RYER (s)

38A04′45″ 122A02′11″

RYERE (nb, s, p)

38A04′28″ 122A01′16″

SPOON (v, s, p, o)

38A04′15″ 121A54′42″

WICK (s)

38A03′30″

Deployment period (Julian Days)

122A14′24″ 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 Conductivity

−5–35ºC 0–70 mS/cm

Temperature Conductivity Salinity Pressure

−2– 35ºC 0.5–65 mS/cm 1–45 0–50 dbar

Turbidity

0.02–2,000 FTU

Current Speed Direction Pressure

0–350 cm/s 0–360 degrees 0–70 m

Temperature Pressure Velocity Heading

−2–35ºC 0–999.9 dbar 0–360 cm/s 0–360 degrees

+/- 0.01 +/- 0.001

+/- 0.001 +/- 0.0001

Ocean Sensors: Os200 CTD

0.01 percent FS 0.02 percent FS 0.03 percent FS 0.50 percent FS

0.001 percent FS 0.001 percent 0.001 percent 0.005 percent

D & A: Optical Backscatterance Sensor (OBS-3)

2.0 percent FS

0.001 FTU

Interocean Systems: S4 Current Meter

2.0 percent FS +/- 2 degrees +/- 0.15 percent

0.2 cm/s 0.5 degrees 4 mm

EG & G: Velocity Meter

0.05ºC 0.5 percent 3 percent +/- 5.0 degrees

0.01ºC 0.2 dbar 0.1 cm/s 1.0 degrees

RD Instruments ADCP: Broad Band and Narrow Band

Velocity Heading

+/- 1,000 cm/s 0–360 degrees

< 1 cm/s 2 degrees

0.1 cm/s 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 rootmean-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 T res ~ 1 hour, where the resonant period, 4L T res ∼ ----------- , 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


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.

Grizzly Bay

Eastern Suisun Bay tidal velocities

N

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

Honker Bay

Schematic not to scale Figure 3. Numerical model simulation of depth-averaged tidal current velocities in Suisun Bay, California, during ebb current (Cheng and others, 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

A 1995

10000 8000 6000 4000

DAYFLOW, IN CUBIC METERS PER SECOND

2000 0 12000

B 1994

10000 8000 6000 4000 2000 0 12000

C 1993

10000 8000 6000 4000 2000 0

DAYFLOW, iN � CUBIC METERS PER SECOND

0

25

50

75

100

125

150 175 200 225 DAYS FROM JANUARY 1

250

275

300

325

350

375

5000

D 4000 3000 2000

Flow resulting from Folsom Dam� gate failure

1000 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 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


Meteorological Conditions

WIND DIRECTION, � IN DEGREES TRUE

BAROMETRIC PRESSURE,� IN MILLIBARS

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 A 1020

1010

1000 360

B

315 270 225 180 135 90

WIND SPEED,� IN METERS PER SECOND

45 0 16 12 10 8 6 4 2 0 40 AIR TEMPERATURE,� IN DEGREES CELSIUS

C

14

D

30

20

10

VISIBLE LIGHT,� IN MICRO EINSTEINS

2000

E

1000

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 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).

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 windwave 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


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), timeseries 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

1 0

2

1

Current speed, meters per second

N Grizzly Bay

51 cm/s

53 cm/s

Rye

r Is

41 cm/s

lan

d

Honker Bay

74 cm/s 60 cm/s

73 cm/s

Mallard Island

Carquinez Strait

Suisun Bay

0 0

RMS current speed

5 KILOMETERS 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).

12


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 Neap tidal current minimum Spring tidal current maximum

0

0.5

Current speed, meters per second

N 17 cm/s

Grizzly Bay

10 cm/s

RMS current speed

9 cm/s

17 cm/s Ry er

Isla

nd

Carquinez Strait

Honker Bay

25 cm/s

24 cm/s Mallard Island

Suisun Bay

0 0

5 KILOMETERS 5 MILES

Figure 7. Near-bed tidal currents obtained from harmonic analysis of single-point-velocity 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).

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� at low water slack 8.0

Maximum salinity� at high water slack

A

SALINITY

6.0

4.0

2.0

Near-surface� Near-bed

AXIAL CURRENT, IN� CENTIMETERS PER SECOND

0.0 100

B

75 50 25

High� water� slack

Low� water� slack

0 -25 -50 -75

-100

SALINITY STRATIFICATION

2.5

C

2.0 1.5 1.0 0.5 0 294.0

294.5

Weaker� stratification� on ebbs

295.0 DAYS FROM JANUARY 1, 1995

295.5

296.0

Stronger� stratification� 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).

14


TIDAL CURRENT SPEED, IN CENTIMETERS PER SECOND

175 150 125 100 75 50 25 0 30 20

BIN 19 SPEED

BIN 19

NEAR SURFACE

(A)

10

(B)

0 -10 -20

RESIDUAL CURRENT SPEED, IN CENTIMETERS PER SECOND

-30 30 20

BIN 13

10 0 -10 -20 -30 30 20

BIN 9

Transverse speed Streamwise speed (positive upstream)

10 0 -10 -20 -30 30 20

BIN 5

10 0 -10 -20 -30 30 20

BIN 1

NEAR BOTTOM

10 0 -10 -20 -30 150

160

170

180

190

200 210 220 230 DAYS FROM JANUARY 1, 1995

240

250

260

270

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

A) Julian � Day 175, 1995 NEAR SURFACE

0.5 METER INCREMENTS

NEAR BOTTOM

6

TRANSVERSE� VELOCITY, IN� -6 CENTIMETERS� 30 PER SECOND 0

-30

0

ALONG-CHANNEL VELOCITY, IN � CENTIMETERS PER SECOND

B) Julian Day 240, 1995 NEAR SURFACE

0.5 METER INCREMENTS

NEAR BOTTOM

-30

0

6 0

TRANSVERSE� VELOCITY, IN� -6 CENTIMETERS� 30 PER SECOND

ALONG-CHANNEL VELOCITY, IN � CENTIMETERS PER SECOND

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


DAYFLOW, IN CUBIC METERS PER SECOND x 103

3

A

2

1

0

10

B

0 BEN BULLS

10

AXIAL SPEED, IN CENTIMETERS PER SECOND

20

10

C

0 10

RYER CUT

20

10

D MID MAL

0 10 20 150

200 250 DAYS FROM JANUARY 1, 1995

300

1995 ADCP LOCATION N

Rio Vista

Riv e

r

C, CUT Mare Island

Carquinez Strait B, BULLS

nt

D, MID

Suisun Bay

0 0

Sa

cra

me

Rive r

u in

aq

San Pablo Bay

o

C, RYER B, BEN

n Sa

Jo

D, MAL 5 MILES

5 KILOMETERS

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

RMS CURRENT SPEED, IN� CENTIMETERS PER SECOND

AXIAL CURRENT SPEED, IN� CENTIMETERS PER SECOND

DAYFLOW, IN� CUBIC METERS PER SECOND

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.

1.5

x10

3

1.0

0.5

0.0 100

DAYS FROM JANUARY 1

B

75 50 25 0 -25 -50 -75 -100 60

C

55 50 45 40 35 7

D

Near surface� Near bed

6 SALINITY

Weak neap tide

Weak neap tide

Weak neap tide

A

5 4 3 2 1

SALINITY STRATIFICATION

0 4

E

3 2 1 0 200

205

210

215

220

225

230

235

240

245

250

255

260

265

270

275

280

285

290

295

300

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).

18


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

DAYFLOW, IN � CUBIC METERS PER SECOND X 10 3

(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

A

Folsom Dam Gate Failure

1.0

0.5

0 5

B

TIDALLY & DEPTH-AVERAGED, ALONG-CHANNEL CURRENT, IN� CENTIMETERS PER SECOND STATION BULLS STATION MAL STATION CUT

0 -5 -10 -15 -20 5

C

0 -5 -10 -15 -20 5

D

0 -5 -10 -15 -20 175

185

195

205

215

225

235

245

255

265

275

DAYS FROM JANUARY 1, 1995

Figure 13. Time-series plot of A, DAYFLOW (California Department of Water Resources, 1986); the tidally averaged, depthaveraged, 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.

20


DAYFLOW, IN� CUBIC METERS PER SECOND X 10 3

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

A Folsom Dam Gate Failure

1.0

0.5

0

15.0

B

SALINITY

12.5

MART� BULLS� MOTH

10.0 7.5 5.0 2.5

RMS DEPTH-AVERAGED� CURRENT SPEED, IN � CENTIMETERS PER SECOND

0.0 60

C

55

50

45

40 175

180

185

190

195

200

205

210 215 220 225 230 235 240 DAYS FROM JANUARY 1, 1995

245

250

255

260

265

270

275

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).

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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