Dissolved Oxygen in Guadalupe Slough and 

Pond A3W, South San Francisco Bay, California, 

August and September 2007

Open-File Report 2008–1097

U.S. Department of the Interior

U.S. Geological Survey

Dissolved Oxygen in Guadalupe Slough and 

Pond A3W, South San Francisco Bay, California, 

August and September 2007

By Gregory G. Shellenbarger, David H. Schoellhamer, Tara L. Morgan, John Y. Takekawa, 

Nicole D. Athearn, and Kathleen D. Henderson

Open-File Report 2008–1097

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Suggested citation:

Shellenbarger, G.G., Schoellhamer, D.H., Morgan, T.L., Takekawa, J.Y., Athearn, N.D., and Henderson, K.D. , 

2008, Dissolved oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and 

September 2007: U.S. Geological Survey Open-File Report 2008–1097, 26 p.
iii

Contents

Abstract...........................................................................................................................................................1

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

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

Acknowledgements..............................................................................................................................3

Methods...........................................................................................................................................................4

First Deployment ...................................................................................................................................4

Second Deployment .............................................................................................................................4

Question 1: Are Dissolved Oxygen Concentrations in Guadalupe Slough Similar to 

Dissolved Oxygen Concentrations in Newark and Mowry Sloughs?......................................4

Technical Considerations ....................................................................................................................4

Results. ....................................................................................................................................................5

Discussion..............................................................................................................................................6

Question 2: Does Discharge From Pond A3W Affect Dissolved Oxygen Concentrations in 

Guadalupe Slough?..........................................................................................................................7

Technical Considerations - First Deployment ..................................................................................7

Results – First Deployment..................................................................................................................7

Discussion – First Deployment .........................................................................................................10

Technical Considerations – Second Deployment..........................................................................10

Results – Second Deployment..........................................................................................................10

Discussion – Second Deployment ...................................................................................................12

Question 3: Does Changing the Volume of Discharge from Pond A3W (One Versus 

Three Culverts) Substantially Affect Dissolved Oxygen Concentrations in 

Guadalupe Slough?........................................................................................................................12

Technical Considerations ..................................................................................................................12

Results. ..................................................................................................................................................13

Discussion............................................................................................................................................15

References Cited..........................................................................................................................................16

Appendix........................................................................................................................................................17
iv

Figures

Figure 1. Map of the study area in southern San Francisco Bay ................................. 2

Figure 2. Graph showing water level and dissolved oxygen (DO) in Newark, Mowry, and 

Guadalupe (middle site) Sloughs ......................................................... 5

Figure 3. Photograph showing Guadalupe Slough surface sediment (tan) lying on top of 

decaying vegetation (black) ............................................................... 6

Figure 4. Graphs showing time series of water depth, specific conductance, and pH in 

pond A3W and in Guadalupe Slough (middle site)....................................... 7

Figure 5. Graphs showing depth, pH, and dissolved oxygen (DO) around lower low water

in Guadalupe Slough and pond A3W during the morning of August 14, 2007 ...... 8

Figure 6. Aerial view of the deployment locations in Guadalupe Slough during both 

deployment periods ........................................................................ 9

Figure 7. Graphs showing overview of Guadalupe Slough (middle site) and pond data 

for the second deployment ............................................................... 10

Figure 8. Graph showing dissolved oxygen (DO) concentrations in Guadalupe Slough 

(middle site) and pond ..................................................................... 11

Figure 9. Graph showing dissolved oxygen (DO) concentrations in the pond and 

Guadalupe Slough (middle site) over the period of study .............................. 13

Figure 10. Graph showing running mean of specific conductance at the three sonde 

locations in Guadalupe Slough ............................................................ 14

Figure 11. Graphs showing dissolved oxygen (DO) in pond A3W and Guadalupe Slough 

(middle site) ................................................................................. 15

Table

Table 1. Distances from the sonde locations to the corresponding slough mouths for 

the first deployment (August) ............................................................ 5
v

Conversion Factors and Datum

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

acre 0.4047 hectare (ha)

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 1.094 yard (yd) 

Datum

Some vertical coordinate information is referenced to the now superseded National standard 

geodetic reference for elevation, the National Geodetic Vertical Datum of 1929 (NGVD 29).
vi

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Dissolved Oxygen in Guadalupe Slough and Pond 

A3W, South San Francisco Bay, California, August and 

September 2007

By Gregory G. Shellenbarger, David H. Schoellhamer, Tara L. Morgan, John Y. Takekawa, Nicole D. Athearn, 

and Kathleen D. Henderson

Abstract

Initial restoration of former salt evaporation ponds under 

the South Bay Salt Pond Restoration Project in San Francisco 

Bay included the changing of water-flow patterns and the 

monitoring of water quality of discharge waters from the 

ponds. Low dissolved oxygen (DO) concentrations became 

evident in discharge waters when the ponds first were opened 

in 2004. This was a concern, because of the potential for 

low-DO pond discharge to decrease the DO concentrations 

in the sloughs that receive water from the ponds. However, 

as of summer 2007, only limited point-measurements of 

DO concentrations had been made in the receiving sloughs 

adjacent to the discharge ponds. In this report, we describe 

two short studies aimed at understanding the natural variability 

of slough DO and the effect of pond discharge on the DO 

concentrations in the sloughs. Pond A3W (a discharge pond) 

and the adjacent Guadalupe Slough were instrumented in 

August and September 2007 to measure DO, temperature, 

conductivity, and pH. In addition, Mowry and Newark Sloughs 

were instrumented during the August study to document DO 

variability in nearby sloughs that were unaffected by pond 

discharge. The results showed that natural tidal variability in 

the slough appeared to dominate and control the slough DO 

concentrations. Water-quality parameters between Guadalupe 

Slough and Mowry and Newark Sloughs could not be directly 

compared because deployment locations were different 

distances from the bay. Pond-discharge water was identified 

in Guadalupe Slough using the deployed instruments, but, 

counter to the previous assumption, the pond discharge, at 

times, increased DO concentrations in the slough. The effects 

of altering the volume of pond discharge were overwhelmed 

by natural spring-neap tidal variability in the slough. This 

work represents a preliminary investigation by the U.S. 

Geological Survey of the effects of pond discharge on 

adjacent sloughs, and the results will be used in designing a 

comprehensive DO study to determine normal variability for 

this region.

Introduction

In March 2003, 16,500 acres of salt evaporation ponds 

owned by the Cargill Corporation in San Francisco Bay were 

purchased for restoration purposes using State, Federal, and 

private funds. The California Coastal Conservancy has been 

leading a collaborative planning effort with the U.S. Fish and 

Wildlife Service (FWS) and the California Department of 

Fish and Game (DFG) to restore some of the ponds to tidal 

action, while providing for flood management, public access, 

and recreation. Other ponds in the system will remain and 

be managed as bird habitat. A long-term restoration plan has 

been developed for the acquired land, and pond restoration 

begins in 2008 (EDAW and others, 2007). The ponds have 

been operated and maintained according to the South Bay Salt 

Pond Restoration Project Initial Stewardship Plan (ISP; Life 

Science!, Inc., 2003) produced for the acquisition. The goal of 

the ISP was to maintain existing habitat and prevent a build up 

of salt in the ponds in a cost-effective manner until the longterm restoration plan is in effect. 
2 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

One series of ponds, managed by FWS in southern San 

Francisco Bay, is the Alviso Salt Pond Complex (fig. 1). 

This complex is made up of 8,300 acres of ponds that have 

been altered into flow-through ponds connected in series, 

under the ISP. The flow-though design of water management 

for the ponds is critical to prevent the production of high 

concentrations of salt in the pond water. Certain ponds in the 

complex serve as intake ponds, drawing water in from San 

Francisco Bay at higher tides. The water then gravity feeds 

through subsets of ponds prior to entering a discharge pond. 

Figure 1. Study area in southern San Francisco Bay. Salt ponds labels that begin with “A” are part of the Alviso Salt Pond 

Complex. The data sondes deployed for the study measured temperature, conductivity, pH, and dissolved oxygen.

The discharge ponds discharge the water directly back to San 

Francisco Bay or to tidal sloughs that terminate in the bay. The 

discharged water, after its transit through the series of ponds, 

is chemically different from bay water because of physical and 

biological processes that occur in the ponds. Water in several 

of the sloughs in southern San Francisco Bay also includes 

discharge from water pollution control plants (WPCP). The 

WPCP discharge is also distinctly different from bay water 

and further complicates determination of the effect of pond 

discharge on the sloughs.
Introduction 3

San Francisco Bay waters are generally considered to 

be high in nutrient concentrations and low in chlorophyll 

concentrations (Cloern, 1996; Wilkerson and others, 2006). 

However, when this water enters the shallow, typically nontidal pond systems, changes in physical habitat contribute 

to conditions that are favorable for algal growth (Thebault 

and others, in review at Wetlands). These conditions lead 

to the establishment of macrophytic algae and the potential 

for periodic chlorophyll blooms in the ponds. In fact, 

large mats of filamentous green algae have been found 

in a number of the ponds. As these mats develop, some 

portion of the algal biomass dies. This leads to localized 

areas of increased respiration in the water column, owing 

to microbial decomposition of the organic matter, which 

results in subsequent decreases in dissolved oxygen (DO) 

concentrations. This issue is typically more severe in the 

summer and can lead to suboxic and anoxic conditions in 

sections of the ponds.

When suboxic or anoxic conditions occur in a discharge 

pond, there is the potential for release of low-DO water to the 

bay or adjacent sloughs, in violation of the discharge permits 

granted by the San Francisco Bay Regional Water Quality 

Control Board. The concern is that releasing large volumes 

of low-DO water into the adjacent sloughs could affect the 

slough-water quality by decreasing the DO concentrations 

to the detriment of the slough biota. Summertime low-DO 

conditions were noticed in parts of several of the FWS 

discharge ponds beginning in 2004. Monitoring has included 

summertime continuous (specifically, 15-min frequency) 

measurements of DO concentrations inside the discharge 

ponds at the discharge location and periodic point samples 

collected in the sloughs. The DO trigger for management 

activity (specified by a decrease in pond discharge) is when 

DO concentrations fall below 3.3 mg/L in greater than 10 

percent of discharge readings, as calculated on a calendarweekly basis. Given that the regulatory requirement is written 

as a DO concentration, instead of the more intercomparable 

and biologically relevant percent saturation, this document 

reports DO in units of concentration. Two issues of concern 

exist with the current monitoring and regulatory strategy: 

(1) some reaeration of the discharge water occurs as the 

water passes through the discharge structure, so the true DO 

concentrations of the water entering the slough from the 

pond are not known; and, (2) the naturally occurring and 

pond-influenced time-series of DO concentrations in the tidal 

sloughs is unknown, so the effect of pond discharges on water 

quality in the receiving sloughs is unknown. In 2007, the 

U.S. Geological Survey (USGS) conducted two short studies 

(referred to in this report as “first deployment” and “second 

deployment”) designed to gather data necessary to address 

to these concerns about the current monitoring and effects of 

pond discharge on the receiving water.

Purpose and Scope

This study and report were designed to explore three 

questions: (1) what are the natural DO concentrations in 

South Bay sloughs that are not subjected to pond discharge, 

and how do they compare to DO concentrations in Guadalupe 

Slough, which receives discharge from Alviso pond A3W; 

(2) is there a discernable impact of pond discharge on slough 

DO concentrations; and (3) does changing the volume of 

pond discharge have a corresponding change in impact on the 

slough DO concentrations?

This report presents the results from a preliminary study 

on the impact of discharge from one pond on dissolved oxygen 

concentrations in an adjacent tidal slough. The results are 

derived from the conditions during two limited deployments 

during late summer 2007. Vertical variation of water quality in 

the water column (both pond and slough) was not measured. 

DO concentrations were measured only inside the pond at the 

discharge structure, so spatial variability of DO within the 

pond was not quantified. This report provides the results of the 

data collection effort and some interpretation of the data with 

regard to management activities.

Acknowledgements

Paul Buchanan, Neil Ganju, and Jessica Wood provided 

assistance with the field work. Clyde Morris and Eric Mruz 

of the Don Edwards San Francisco Bay National Wildlife 

Refuge provided access and information on pond A3W. John 

Johnston of California State University, Sacramento, kindly 

analyzed our biochemical oxygen demand (BOD) samples. 

Dave Grabiec provided us with data from the Sunnyvale 

Water Pollution Control Plant. Eric Mruz, Tara Schraga, and 

Lisa Olsen provided reviews that improved the manuscript. 

Funding was provided by the U.S. Geological Survey Priority 

Ecosystem Science Program.
4 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

Methods

Data sondes that measured temperature, conductivity, 

pH, and DO (YSI 6920v2, YSI, Incorporated, Yellow Springs, 

Ohio) were deployed about 0.75 m above the bottom in the 

thalweg (deepest point) of some southern San Francisco 

Bay sloughs. Three sondes were deployed in Guadalupe 

Slough: one landward, one adjacent to (called middle), and 

one seaward of the pond A3W discharge structure (figs. 1

and 6). The middle sonde was deployed intentionally in the 

mixing zone of the slough and discharged pond water. The 

USGS maintained a data sonde just on the pond side of the 

A3W discharge culverts as part of the FWS self-monitoring 

program (Hydrolab 4a, Hach Company, Loveland, Colorado). 

This instrument recorded measurements every 15 minutes. 

Calibration of these sondes prior to deployment followed the 

manufacturer’s recommended methods and conformed to 

Wagner and others (2006). Checks were conducted after the 

deployment period to verify that sondes were still calibrated. 

The deployments were of short duration, and no fouling or 

drift corrections were required. All data collected from the 

sondes were accepted with no edited data points. An acoustic 

Doppler velocimeter (Argonaut-XR ADV, Sontek/YSI, Inc., 

San Diego, California) was deployed in Guadalupe Slough. 

Biochemical oxygen demand (BOD) values for the Sunnyvale 

WPCP discharge reported by the City of Sunnyvale (David 

Grabiec) were carbonaceous BOD5

 (5-day, CBOD5) analyzed 

following Standard Methods 5210 (American Public Health 

Association, 2006). Estimates of pond discharge were obtained 

from PONDCALC (Shellenbarger and others, 2007), a tool 

developed for FWS by the USGS to calculate pond discharge 

based on water surface elevation in the pond and tidal stage in 

the slough.

First Deployment

The first deployment occurred August 13–17, 2007. 

Instruments were deployed in Guadalupe, Newark, and Mowry 

Sloughs and recorded measurements every 15 minutes. One 

sonde was deployed in each of Mowry and Newark Sloughs 

(fig. 1). These sites served as control sites, because they 

experienced neither pond nor water pollution control plant 

discharge. Guadalupe Slough receives discharge from the City 

of Sunnyvale WPCP landward of our deployment locations. 

The Sontek ADV recorded water depth above its pressure 

transducer every 15 minutes. Water velocities were not 

measured successfully in August. 

Second Deployment

Data sondes were deployed in Guadalupe Slough during 

September 11–24, 2007, (figs. 1 and 6). These instruments 

recorded measurements every 7.5 minutes. The Sontek 

ADV measured and recorded water depth above its pressure 

transducer and depth-integrated velocity in the slough every 

7.5 minutes. Several water samples were collected to measure 

biochemical oxygen demand (BOD) on September 13: three 

samples were collected from different spots in pond A3W 

(fig. 6): sites BOD 1 (southeastern side near a thick algae mat), 

BOD 2 (adjacent to the discharge structure), and BOD 3 (at 

the levee bend north of the discharge structure). Two samples 

were collected from Guadalupe Slough (both collected from 

the NASA dock just landward of the pond A3W discharge 

at BOD 4, one from early flood and the second about 2 

hours later during flood tide). These unfiltered samples 

were analyzed for BOD5

 (5-day, sum of carbonaceous and 

nitrogenous demand) by Dr. John Johnston, California State 

University, Sacramento, following Standard Method 5210 

(American Public Health Association, 2006). The difference 

in analysis methods between the pond and slough samples 

(BOD5 analyzed by John Johnston) and those of the Sunnyvale 

WPCP (CBOD5 analyzed by the City of Sunnyvale) suggests 

that the numbers are not directly comparable. However, BOD5

is likely to overestimate oxygen demand, relative to CBOD5. 

Since our BOD5 results are quite low, this difference did not 

affect the interpretation of these data.

Question 1: Are Dissolved Oxygen 

Concentrations in Guadalupe 

Slough Similar to Dissolved Oxygen 

Concentrations in Newark and Mowry 

Sloughs?

Technical Considerations

•	 This question was addressed only during the first 

deployment.

•	 Guadalupe Slough is affected by discharge from pond 

A3W, pond A5, and the City of Sunnyvale water pollution 

control plant (WPCP).
Question 1 5

Table 1. Distances from the sonde locations to the 

corresponding slough mouths for the first deployment (August).

Site

Distance to 

slough mouth 

(meters)

Newark Slough 1,800

Mowry Slough 2,140

Guadalupe Slough-seaward 3,800

Guadalupe Slough-middle 4,090

Guadalupe Slough-landward 4,320

•	 Newark and Mowry Sloughs serve as control sites, 

because they experience neither pond nor WPCP 

discharge.

•	 Guadalupe Slough is longer than the control sites and the 

measurement site was further from the bay (table 1).

•	 Pond A3W discharged through one of three 48-inch 

culverts, and the flap gate on the slough side had a 

10-inch opening above the invert to allow some flow into 

the pond during higher tides in the slough.

•	 The pond A5 discharge was seaward of our Guadalupe 

Slough measurement sites.

Results

•	 Average DO concentrations were greatest in Newark 

Slough and least in Guadalupe Slough (fig. 2).

•	 DO varied semidiurnally, and the lowest DO 

concentrations occurred during low tides and the highest 

DO concentrations during high tides. This indicates that 

bay water generally has higher DO concentrations than 

slough water. Low-DO slough water moves toward the 

bay during ebb tide, and higher-DO water moves from the 

bay into the sloughs during flood tide.

•	 DO increased to the north (toward the Golden Gate) in 

the South Bay. DO concentrations were 6.2–6.6 mg/L 

(85–92 percent saturation) on July 23, 6.8–6.9 mg/L 

(94–95 percent saturation) on August 22 off Calaveras 

Point in South Bay (fig. 1) and generally increased 

northward (USGS Polaris cruise data, http://sfbay.wr.usgs.

gov/access/wqdata/query/index.html).

•	 The water level in pond A3W was -0.8 ft (NGVD 29) on 

August 13.

1

2

3

4

Water Depth (m)

2

3

4

5

6

7

DO (mg/L)

20

40

60

80

100

DO (percent saturation)

14 15 16 17

AUGUST 2007

Newark

Mowry

Guadalupe

Figure 2. Water level and dissolved oxygen (DO) in Newark, Mowry, and Guadalupe (middle site) Sloughs.
6 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

Discussion

•	 Potential explanations prior to data collection in the 

first deployment and discussions based on collected 

data after the first deployment for the presence of lower 

DO concentrations in Guadalupe Slough than in control 

sloughs include (explanations other than pond A3W 

discharge):

1. Measurement sites in Guadalupe Slough were 

further from the bay than in the control sloughs 

(table 1). DO in tidal creeks often is depleted, 

relative to open bay waters (MacPherson and others, 

2007), and DO concentrations tend to decrease with 

increasing distance from open water (Boto and Bunt, 

1981). Thus, lower DO concentrations in Guadalupe 

Slough, relative to the control sloughs, could be due 

to increased distance from bay water.

2. The Sunnyvale WPCP could release water with 

lower DO than that measured in Guadalupe 

Slough. For the study period, however, the 

average discharge from the Sunnyvale WPCP was 

15 MGD, and the average effluent DO was 4 mg/L 

(50 percent saturation, David Grabiec, City of 

Sunnyvale WPCP, written commun., October 5, 

2007). This DO concentration was higher than 

the average concentration measured at any of 

the three Guadalupe Slough sites. PONDCALC 

(Shellenbarger and others, 2007) estimated an 

average of 15 MGD discharged from the pond 

August 13–17. Thus, the discharge volume of the 

pond and WPCP were similar, so it is not expected 

that the WPCP effluent chemistry could be masked 

completely by pond discharge. 

3. Biochemical oxygen demand (BOD) of pond 

discharge or Sunnyvale WPCP discharge potentially 

could decrease DO in Guadalupe Slough. However, 

the average Sunnyvale WPCP effluent BOD 

for August 13–15 was 3 mg/L (David Grabiec, 

City of Sunnyvale WPCP, written commun., 

October 5, 2007). The effluent BOD was low 

enough that, assuming reasonable deoxygenation 

and reaeration coefficients, it should produce an 

increase (not a decrease) in DO in the receiving 

waters after discharge (Dr. John Johnston, CSUS 

Civil Engineering, written commun., September 13, 

2007). Later in this report we describe some limited 

measurements of BOD in A3W and Guadalupe 

Slough that suggest that BOD in the pond water and 

discharge is not a significant consumer of DO.

4. Sediment oxygen demand (SOD) in Guadalupe 

Slough might have been larger than in the control 

sloughs. We found a layer of decaying vegetation 

below the surface sediment (fig. 3) in Guadalupe 

Slough that could act as a source of SOD; however, 

SOD was not measured.

Figure 3. Guadalupe Slough surface sediment (tan) lying on 

top of decaying vegetation (black).
Question 2 7

Question 2: Does Discharge From 

Pond A3W Affect Dissolved Oxygen 

Concentrations in Guadalupe Slough?

Technical Considerations - First Deployment

•	 Pond A3W discharged through one of three 48-inch 

culverts. 

•	 The flap gate on the slough side of the culvert had a 

10-inch opening above the invert to allow some muted 

tidal flow into the pond during higher tides in the slough.

Results – First Deployment

•	 Specific conductance (SC) and pH proved to be good 

indicators of pond water in the slough. The average SC of 

the pond was slightly greater than 45,000 μS/cm (fig. 4), 

the SC of bay water was 40,000 μS/cm, and the SC of the 

landward slough water was no more than 10,000 μS/cm; 

the low SC in the slough probably results from the low 

SC of water discharged from the WPCP (not measured in 

this study but assumed to be fresh water). The average pH 

of the pond was about 8.7 and the average pH of slough 

water was about 8.2. The pH time series offers more 

detail so it could be used to differentiate pond water in the 

slough. At high tide, water from the bay filled the slough 

and entered the pond through the slightly open culvert, 

lowering pH to the bay value (roughly a value of 8). 

1

2

3

4

Water depth (m)

1

2

3

4

5 x 10 4

Specific conductance

 (μS/cm)

7.5

8

8.5

9

9.5

pH

14 15 16 17

AUGUST 2007

Guadalupe

A3W

Figure 4. Time series of water depth, specific conductance, and pH in pond A3W and in Guadalupe Slough (middle site).
8 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

1

1.5

2

2.5

3

Water depth (m)

7.5

8

8.5

9

pH

06:00 09:00 12:00

1

2

3

4

5

DO (mg/L)

Time, 14 August

Seaward

Middle

Landward

A3W

Figure 5. Depth, pH, and dissolved oxygen (DO) around lower low water in Guadalupe Slough and pond A3W during 

the morning of August 14, 2007. These results were typical of seven of the eight low tides observed during the first 

deployment.

At low tide, bay water was pulled out of the pond and 

slough and pH rose to the pond value (approaching a 

value of 9).

•	 During seven of the eight low tides observed, slightly 

aerated pond water entered the slough (fig. 2). During 

these low tides, SC (fig. 4) and pH (fig. 5) spiked when 

high-SC and high-pH water from the pond appeared at 

the middle site in the slough adjacent to the discharge 

structure. pH did not increase either landward or seaward 

of the discharge point (0900 h, fig. 5). Photosynthesis 

increased DO in the pond in the late morning when lower 

low water (LLW) occurred. DO increased in the slough 

at LLW concurrent with the spike in pH (0900 h, fig. 5). 

Discharged pond water hit the culvert flap gate, passed 

through the trash rack, and flowed down a wide shallow 

channel into the slough. Aeration along this flow path 

increased DO roughly 1 mg/L. The subsequent floodtide 

transported the higher pH and DO water to the landward 

site (red line, fig. 5). The higher pH and DO water was 

not observed at the seaward site.

•	 The high-pH water that came out of the pond during low 

tide was transported upstream during the subsequent 

floodtide. During the following ebb tide, that water 

returned to the middle site, increasing pH at that location 

(fig. 4). The ebb tide pH peak was lower and more diffuse 

than the flood tide pH, owing to mixing and dilution.
Question 2 9

Figure 6. The deployment locations in Guadalupe Slough during both deployment periods. The seaward sonde, middle 

sonde, and landward sonde sites were the locations of the conductivity, temperature and depth sondes, while “Sontek” 

was the location of the current meter. BOD sites were locations where the BOD samples were collected on September 

13; BOD 1–3 were in pond A3W, while BOD 4 was in Guadalupe Slough.
10 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

Figure 7. Overview of Guadalupe Slough (middle site) and pond data for the second deployment. Pond A3W discharge 

gate operations changed on the afternoon of September 13 and 20 (see text for details).

Discussion – First Deployment

•	 Pond discharge affected the slough at low tide when pond 

discharge was greatest and dilution by slough water was 

smallest.

•	 It is unknown whether the correspondence of minimum 

slough DO and low water was caused by pond discharge, 

upstream Sunnyvale WPCP, or sediment oxygen demand. 

If the pond discharge were responsible, closing the pond 

discharge for several days should cause DO to increase 

in the slough. If there were no increase, then either the 

pond discharge was not responsible or the pond discharge 

was not closed long enough to allow recovery of DO. 

This experiment could be the basis of a subsequent 

deployment, if it would be ecologically feasible to close 

the pond.

•	 Scope of findings: The results were for only one tidal 

condition and one discharge point. Discharge points from 

other ponds are located closer to or further from the bay 

and upstream freshwater sources (including WPCPs). 

This deployment helped explain details of the pond A3W 

discharge, and it served as a reconnaissance for deploying 

these instruments and for designing a comprehensive 

monitoring program for DO in the sloughs.

Technical Considerations – Second Deployment

•	 For pond A3W discharge, three 48-inch culverts were 

open prior to the start of the deployment until the 

afternoon of September 13. One 48-inch culvert remained 

opened from the afternoon of September 13 until the 

afternoon of September 20 (the other two culverts were 

closed). The two closed culverts were reopened on 

the afternoon of September 20, and all three culverts 

remained opened though the end of the deployment on 

September 24. 

•	 The pond was closed to direct water input from the slough 

(the pond was not opened to tidal action).

Results – Second Deployment

•	 DO in the slough varied semidiurnally (fig. 7E), and the 

lowest DO concentrations occurred near low tide and 

highest DO concentrations during high tide. However, not 

all low tides were associated with low DO (fig. 8), mostly 

owing to the discharge of high DO pond water (see below 

for a more detailed description of DO dynamics in pond 

A3W). In general, bay water had greater DO than slough 

0

2

4

Depth (m)

15

20

25

Temp (°C)

0

3

6 x 104

Specific 

conductance

(μS/cm)

7

8

9

pH

0

6

12

11 13 15 17 19 21 23 25

September 2007

DO (mg/L)

Middle

A3W

A

B

C

D

E
Question 2 11

water. Low DO slough water moved toward the bay 

during ebb tide and higher DO water moved from the bay 

into the slough during flood tide.

•	 DO concentrations at the discharge structure in the pond 

mostly varied diurnally. However, weaker semidiurnal 

variations did occur. DO peaks at the discharge structure 

in the pond typically corresponded to low tide in the 

slough, with the larger peaks associated with the lower 

tides (fig. 8). 

•	 Water temperatures at all locations were significantly 

lower at the end of the study than at the beginning 

(fig. 7B). 

•	 There was a precipitation event during the study period. 

Moffett Field (fig. 1) experienced 0.74 cm of rainfall on 

September 22 (http://www.wunderground.com/). Rainfall 

could have changed the flow, conductivity, and mixing 

dynamics in the slough and pond.

•	 Similar to the first deployment, pond discharge 

was identified clearly in the slough on the basis of 

conductivity, pH, and DO data.

•	 The increase in DO concentrations at the middle and 

landward locations that typically accompanied the 

beginning of flood tide peaked at the middle site prior 

to the landward site (roughly 30 minutes after low 

tide). This is suggestive of high-DO pond water (higher 

than the slough) discharging to the slough and being 

transported upstream. See below for an explanation for 

this higher-DO pond water.

•	 The DO concentration averaged over the entire study 

period was significantly lower in the pond than in the 

slough (p<0.0001, t-test).

•	 The BOD in the slough was 4–5 mg/L (at BOD 4), while 

the BOD in pond A3W was approximately 19 mg/L at 

BOD 1, approximately 1 mg/L at BOD 2 (discharge 

structure), and approximately 6 mg/L at BOD 3 (Dr. John 

Johnston, CSUS Civil Engineering, written commun., 

September 18, 2007). The Sunnyvale WPCP effluent 

data show a carbonaceous BOD of 2.2 mg/L and a DO 

concentration of 7.38 mg/L on the same day that our BOD 

samples were collected (September 13; Dave Grabiec, 

Sunnyvale WPCP, written commun., November 27, 2007).

Figure 8. Dissolved oxygen (DO) concentrations in Guadalupe Slough (middle site) and pond. The red curve is the water 

depth (meters) above the current meter and corresponds to the tidal level. These data run from noon on September 11 until 

noon on September 14. When water level was decreasing, the tide was ebbing. When water level was increasing, the 

tide was flooding. The depicted results are typical for spring (displayed) and neap tidal conditions, although the dissolved 

oxygen (DO) response to discharge during neap conditions is muted.

0

1

2

3

4

5

6

7

12 13 14

SEPTEMBER 2007

DO (mg/L)

Middle

A3W

Slough depth (m)
12 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

•	 The water-surface elevation (NGVD29) in pond A3W 

was about -1.65 ft for September 11–13, -1.55 ft for 

September 14–17, -1.40 ft for September 18–20, and 

-1.50 ft for September 21–24 (Eric Mruz, FWS, written 

commun., September 18, 2007).

•	 DO increased to the north (toward the Golden Gate) 

in South Bay. In the bay, DO was 6.4–6.6 mg/L 

(83-85 percent saturation) on September 21 off Calaveras 

Point and generally increased northward (USGS Polaris

cruise data, http://sfbay.wr.usgs.gov/access/wqdata/

query/index.html). DO in the Sunnyvale WPCP effluent 

on the same day was 6.55 mg/L (74 percent saturation, 

Dave Grabiec, Sunnyvale WPCP, written commun., 

November 27, 2007).

Discussion – Second Deployment

•	 DO concentrations in pond A3W were not uniform in 

time or space. 

•	 DO concentrations throughout the pond were lowest 

in the early morning (pre-dawn) when photosynthetic 

rates were minimal and highest in the late afternoon 

or earlier evening after the phytoplankton had been 

photosynthetically active all day. 

•	 Spatially, the lowest DO concentrations occurred near 

the algal mats (Hansen, 2004; Takekawa and others, 

unpublished data, 2004–07) that collect around the 

discharge structure (the down-wind corner of the pond). 

Other regions of the pond away from the algal mats 

tended to have higher DO concentrations (Hansen, 2004; 

Takekawa and others, unpublished data, 2004–07). The 

spatial and temporal variability led to dramatic changes 

in the DO concentrations of the water discharging from 

the pond into the slough. Water that discharged initially 

from the pond as the tide fell in the slough came from 

the region of the pond near the algal mats (around the 

discharge structure). This water had relatively low DO 

concentrations. As the tide continued to fall and the 

discharge rates from the pond increased, water was 

pulled from regions of the pond that are further from the 

discharge structure and algal mats. This water had higher 

DO concentrations than the water that was near the algal 

mats. The water discharging from the pond during the low 

tide later in the day had higher DO concentrations than 

the water that discharged earlier in the day because of the 

oxygenation of the shallow pond water by photosynthetic 

organisms. 

•	 Combined, the factors led to a generally mixed 

semidiurnal DO signal in the discharge as measured in 

A3W at the discharge structure, with discharges earlier in 

the day having lower DO concentrations than afternoon 

discharges and the discharge water increasing in DO 

concentration with increasing discharge period (fig. 8). 

•	 DO concentrations in pond A3W were lower than in 

Guadalupe Slough, with the 10th percentile over the 

September study of 0.11 mg/L in the pond and 1.76 mg/L, 

1.73 mg/L, and 1.99 mg/L for landward, middle, and 

seaward sites, respectively, in the slough. 

•	 The slough BOD samples were near the BOD 

concentrations of the WPCP effluent (that is, low). The 

samples from the pond were variable. Water from the 

BOD 1 site was collected directly adjacent to a dying, 

anoxic algal mass and would be expected to have an 

increased BOD (although a value of about 19 mg/L is 

not dramatically high; John Johnston, CSUS, written 

commun., 2007). The BOD for site BOD 3 was roughly 

the same as the BOD in the slough, while the sample 

from the discharge location in the pond showed extremely 

low BOD. This suggests that the pond discharge was not 

contributing significant BOD to the slough. 

•	 Sediment oxygen demand (SOD) in pond A3W and 

Guadalupe Slough was not quantified.

Question 3: Does Changing the 

Volume of Discharge from Pond 

A3W (One Versus Three Culverts) 

Substantially Affect Dissolved Oxygen 

Concentrations in Guadalupe Slough?

Technical Considerations

•	 This question was only addressed during the second 

deployment.

•	 If pond discharge were responsible for substantially 

affecting DO concentrations in the slough, then altering 

the pond discharge from one to three culverts (and 

back) should show a distinct change in slough DO 

concentrations (and other constituents) that correspond to 

the changes in volume of pond discharge. 
Question 3 13

Figure 9. Dissolved oxygen (DO) concentrations in the pond and Guadalupe Slough (middle site) over the period of study. 

Discharge from the pond was changed on September 13 (from three to one culvert) and on September 20 (one to three 

culverts).

0

1

2

3

4

5

6

7

8

9

10

11 13 15 17 19 21 23 25

SEPTEMBER 2007

DO (mg/L)

Middle

A3W

Slough depth (m)

Results

•	 Daily pond A3W discharge estimates are as follows 

(estimates from PONDCALC, Shellenbarger and others, 

2007): September 11–13, 27.6 MGD (million gallons 

per day, three culverts discharging); September 14–17, 

6.6 MGD (one culvert discharging); September 18–20, 

5.4 MGD (one culvert discharging); September 21–24, 

26.5 MGD (three culverts discharging). When all three 

culverts were discharging, the daily discharge from pond 

A3W during this study was about three times that of the 

Sunnyvale WPCP discharge estimate of 8.7 MGD (range 

6.9–10.4 MGD; Dave Grabiec, Sunnyvale WPCP, written 

commun., November 27, 2007). 

•	 Typically during spring low tides, water with DO higher 

than the DO in the slough discharged from the pond, 

while during neap tides, the DO concentrations were 

almost always higher in the slough than the pond (fig. 9). 

The higher DO values at the discharge structure in the 

pond, particularly around spring low tides, likely resulted 

from the transport of higher DO pond water toward the 

discharge location because of the longer discharge period 

during the lower tides (see above explanation for higher 

DO water near the discharge structure).
14 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

•	 Specific conductivity is a conservative tracer of pond 

water (specifically, the slough conductivity changes only 

due to mixing with water of different conductivities, such 

as bay or pond water; we assume that evaporation in the 

slough has a negligible effect in this case). Figure 10

shows the running mean (24-hour window) of specific 

conductance for the three slough sonde locations 

(Seaward, Middle, and Landward). Slough conductivities 

began to decrease coincident with the A3W discharge 

change from three to one culvert. However, slough 

conductivities increased to pre-change levels prior to the 

change back from one culvert to three discharge culverts.

•	 There was no clear change in slough DO concentrations 

when discharge from A3W was changed from three 

culverts to one or the reverse (fig. 11). DO concentration 

variability appeared to be controlled more by tide (spring 

versus neap) than by culvert management.

11 13 15 17 19 21 23 25

2.6

2.7

2.8

2.9

3

3.1

3.2

3.3

3.4

3.5 x 104

Specific conductance (μS/cm)

Seaward

Middle

Landward

September 2007

Figure 10. Running mean of specific conductance at the three sonde locations in Guadalupe Slough. The window for the 

running mean is 24 hours. Dotted vertical lines represent roughly when the A3W discharge operations were changed: on 

the afternoon of September 13 (reduced from three to one culvert) and on the afternoon of September 20 (increased from 

one to three culverts).
Question 3 15

12 13 14 15 16

0

1

2

3

4

5

6

7

8

DO (mg/L)

19 20 21 22

0

1

2

3

4

5

6

7

8

DO (mg/L)

Middle

A3W

A

B

September 2007

A3W discharge through 3 culverts A3W discharge through 1 culvert

A3W discharge through 1 culvert A3W discharge through 3 culverts

Middle

A3W

Figure 11. Dissolved oxygen (DO) in pond A3W and Guadalupe Slough (middle site). The dotted line (A) shows the 

approximate time of change from three to one discharge culvert, while the dashed line (B) shows the approximate time of 

change from one to three discharge culverts.

Discussion

•	 Pond discharge affected the slough DO concentrations the 

most during lower tides when pond discharge was greatest 

and dilution by slough water was smallest.

•	 Spring-neap tidal changes and potential precipitation 

effects appeared to have a larger impact on slough 

DO concentrations than the change from one to three 

discharging culverts (fig. 7E).

•	 In spite of the large difference in volume discharge from 

A3W between one or three culverts, there was no clear 

DO signal change associated with changing management 

of A3W discharge during this study (figs. 9 and 11). The 

variability of the data due to the spring-neap tidal cycle, 

and perhaps a change in the weather, overwhelmed the 

ability to see changes in slough DO concentrations that 

may have occurred because of changing pond-volume 

discharge.

•	 In addition, the changing conductivities in the slough 

appeared to be more related to the spring-neap tidal 

cycle than changing the volume discharge of higher 

conductivity pond water (fig. 10). Tidal energy began to 

increase by September 18 and so did conductivity, despite 

no change in the number of open culverts. Increased 

tidal energy can increase salinity intrusion up the slough. 

Another possible explanation was that pond discharge 

(high-conductivity water) increased as low tide got 

lower, but most of the conductivity increase in the slough 

happened before the two additional culverts were opened 

(the opening of which quadruples the pond discharge 

during this period; fig. 10). Even though the decrease in 

slough conductivities was coincident with the 75-percent 

decrease in discharge volume of high conductivity pond 

water, the subsequent rebound of conductivity in the 

slough began to happen 3 days before the pond discharge 

volume was increased back to over 25 MGD. If a distinct 

effect on slough conductivities from the pond discharge 

could not be seen with a conservative tracer like salt, it 

likely would be more difficult to identify effects with nonconservative dissolved oxygen.
16 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

•	 Whether the co-occurrence of minimum slough DO 

and low water was caused by pond discharge, upstream 

Sunnyvale WPCP, and/or sediment oxygen demand is 

unknown.

•	 Scope of findings: The second deployment period 

included a single spring-neap tidal cycle, a significant 

drop in air temperature, and a precipitation event. This 

deployment helped to understand the effects of changing 

pond A3W discharge, and it served to inform designing 

a comprehensive monitoring program for DO in the 

sloughs. A comprehensive DO monitoring and analysis 

program would include different seasons, tides, pond 

operations, and additional ponds.

References Cited

American Public Health Association, 2006, Standard 

methods for the examination of water and wastewater 

(21st ed.): Washington, D.C., American Public Health 

Association, American Water Works Association, and Water 

Environment Federation, http://www.standardmethods.org/

Boto, K.G., and Bunt, J.S., 1981, Dissolved oxygen and pH 

relationships in northern Australian mangrove waterways: 

Limnology and Oceanography, v. 26, no. 6, p. 1176–1178.

Cloern, J.E., 1996, Phytoplankton bloom dynamics in coastal 

ecosystems: A review with some general lessons from 

sustained investigation of San Francisco Bay, California: 

Reviews of Geophysics, v. 34, no. 2, p. 127–168.

EDAW, Philip Williams and Associates, Ltd., H.T. Harvey 

and Associates, Brown and Caldwell, and Geomatrix, 

2007, South bay Salt Pond Restoration Project Final 

Environmental Impact Statement/Report Volume 1,

http://www.southbayrestoration.org/EIR

Hansen, S.R., 2004, Evaluation of the potential for reductions 

in dissolved oxygen associated with circulation of 

saline water from pond A18: S.R. Hansen & Associates, 

unpublished report, DO Evaluation 11-07-04.

Life Science!, Inc., 2003, South Bay Salt Ponds Initial 

Stewardship Plan, http://www.southbayrestoration.org/

pdf_files/ISP.pdf, 251 p.

MacPherson, T.A., Cahoon, L.B., and Mallin, M.A., 2007, 

Water column oxygen demand and sediment oxygen flux: 

patterns of oxygen depletion in tidal creeks. Hydrobiologia, 

v. 586, p. 235–248.

Shellenbarger, G.G., Schoellhamer, D.H., and Lionberger, 

M.A., 2007, PONDCALC—A tool to estimate discharge 

from the Alviso Salt Ponds, South San Francisco Bay, 

California: U.S. Geological Survey Scientific-Investigations 

Report 2007–5005, 12 p.

Thebault, J., Schraga, T.S., Cloern, J.E., and Dunlavey, E.G., 

In Review, Primary production and carrying capacity of 

former salt ponds after reconnection to San Francisco Bay: 

Wetlands.

Wagner, R.J., Boulger, R.W., Oblinger, C.J., and Smith, B.A., 

2006, Guidelines and standard procedures for continuous water-quality monitors: station operation, record 

computation, and data reporting: U.S. Geological Survey 

Techniques and Methods 1-D3, 51 p., accessed January 15, 

2008, at http://pubs.water.usgs.gov/tm1d3

Wilkerson, F.P., Dugdale, R.C., Hogue, V.E., and Marchi, A., 

2006, Phytoplankton blooms and nitrogen productivity in 

San Francisco Bay: Estuaries and Coasts, v. 29, no. 3, p. 

401–416.
Appendix 17

Appendix

In the following plots, all of the collected sonde data 

for both the first deployment and the second deployment 

are presented. The data include temperature, specific 

conductance, pH, DO, DO percent saturation, water 

height above the Sontek ADV, and velocity. Data labeled 

“Landward”, “Middle”, and “Seaward” refer to the Guadalupe 

Slough sites. Data from the Sontek ADV (water height and 

velocity) are also from Guadalupe Slough. No dissolved 

oxygen percentage data were obtained from pond A3W. 

Please refer to the full report for additional details.

First Deployment (August 13–17, 2007)

Guadalupe Slough and Control Sloughs Newark 

and Mowry

19

19.5

20

20.5

21

21.5

22

22.5

23

23.5

14 15 16 17

AUGUST 2007

Temperature (degrees C)

Newark

Mowry

Middle

Figure A1. Temperature in Guadalupe Slough and control sloughs during the first deployment.
18 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

7.6

7.8

8

8.2

8.4

8.6

8.8

9

9.2

9.4

14 15 16 17

AUGUST 2007

pH

Newark

Mowry

Middle

Figure A2. Specific conductance in Guadalupe Slough and control sloughs during the first deployment.

7.6

7.8

8

8.2

8.4

8.6

8.8

9

9.2

9.4

14 15 16 17

AUGUST 2007

pH

Newark

Mowry

Middle

Figure A3. pH in Guadalupe Slough and control sloughs during the first deployment.
Appendix 19

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

14 15 16 17

AUGUST 2007

DO (mg/L)

Newark

Mowry

Middle

Figure A4. Dissolved oxygen (DO) in Guadalupe Slough and control sloughs during the first deployment.

20

30

40

50

60

70

80

90

14 15 16 17

AUGUST 2007

DO (percent saturation)

Newark

Mowry

Middle

Figure A5. Dissolved oxygen (DO) percent saturation in Guadalupe Slough and control sloughs during the first 

deployment.
20 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

Guadalupe Slough and Discharge Pond A3W

1

1.5

2

2.5

3

3.5

4

14 15 16 17

AUGUST 2007

Height of water above instrument (m)

Figure A6. Height of the water above the Sontek acoustic Doppler velocimeter in Guadalupe Slough during the first 

deployment.

0

2

4

Depth (m)

15

20

25

Temp (°C)

0

3

6 x 104

Specific 

conductance

(μS/cm)

7

8

9

pH

0

6

12

11 13 15 17 19 21 23 25

September 2007

DO (mg/L)

Middle

A3W

A

B

C

D

E

Figure A7. Temperature in Guadalupe Slough and pond A3W during the first deployment.
Appendix 21

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5 x 104

14 15 16 17

AUGUST 2007

Specific conductance (μS/cm)

Landward

Middle

Seaward

A3W

Figure A8. Specific conductance in Guadalupe Slough and pond A3W during the first deployment.

7.6

7.8

8

8.2

8.4

8.6

8.8

9

9.2

9.4

14 15 16 17

AUGUST 2007

pH

Landward

Middle

Seaward

A3W

Figure A9. pH in Guadalupe Slough and pond A3W during the first deployment.
22 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

0

1

2

3

4

5

6

14 15 16 17

AUGUST 2007

DO (mg/L)

Landward

Middle

Seaward

A3W

Figure A10. Dissolved oxygen (DO) in Guadalupe Slough and pond A3W during the first deployment.

20

30

40

50

60

70

80

14 15 16 17

AUGUST 2007

DO (percent saturation)

Landward

Middle

Seaward

Figure A11. Dissolved oxygen (DO) percent saturation in Guadalupe Slough during the first deployment.
Appendix 23

Second Deployment (September 11–24, 2007)

0.5

1

1.5

2

2.5

3

3.5

4

11 13 15 17 19 21 23 25

SEPTEMBER 2007

Height of water above instrument (m)

Figure A12. Height of the water above the Sontek acoustic Doppler velocimeter in Guadalupe Slough during the 

second deployment.

-60

-40

-20

0

20

40

60

80

11 13 15 17 19 21 23 25

SEPTEMBER 2007

Velocity (cm/s)

East

North

Vertical

Figure A13. Velocity of the water in Guadalupe Slough during the second deployment.
24 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

16

17

18

19

20

21

22

23

24

25

11 13 15 17 19 21 23 25

SEPTEMBER 2007

Temperature (degrees C)

Landward

Middle

Seaward

A3W

Figure A14. Temperature in Guadalupe Slough and pond A3W during the second deployment.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5 x 104

11 13 15 17 19 21 23 25

SEPTEMBER 2007

Specific conductance (μS/cm)

Landward

Middle

Seaward

A3W

Figure A15. Specific conductance in Guadalupe Slough and pond A3W during the second deployment.
Appendix 25

7.2

7.4

7.6

7.8

8

8.2

8.4

8.6

8.8

9

11 13 15 17 19 21 23 25

SEPTEMBER 2007

pH

Landward

Middle

Seaward

A3W

Figure A16. pH in Guadalupe Slough and pond A3W during the second deployment.

0

1

2

3

4

5

6

7

8

9

10

11

11 13 15 17 19 21 23 25

SEPTEMBER 2007

DO (mg/L)

Landward

Middle

Seaward

A3W

Figure A17. Dissolved oxygen (DO) in Guadalupe Slough and pond A3W during the second deployment.
26 Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007

0

20

40

60

80

100

120

11 13 15 17 19 21 23 25

SEPTEMBER 2007

DO (percent saturation)

Landward

Middle

Seaward

Figure A18. Dissolved oxygen (DO) percent saturation in Guadalupe Slough during the second deployment.
Manuscript approved for publication, February 6, 2008

Prepared by the USGS Publishing Network, 

Bobbie Jo Richey 

Yvonne Roque

Carol Sanchez

Sharon Wahlstrom

For more information concerning the research in this report, contact the 

California Water Science Center Director, 

U.S. Geological Survey,

6000 J Street, Placer Hall

Sacramento, California 95819

http://ca.water.usgs.gov
Shellenbarger and others— Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007—OFR 2008–1097