San

Francisco

Los Angeles

Sacramento

U.S. Geological Survey

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 03-370

Prepared in cooperation with the California Department of Water Resources

Carbon Fluxes, Water Levels, and Related Environmental Data,

Twitchell Island, Sacramento-San Joaquin Delta, California,

November 1992 through September 1995

DELTA

AREA
Carbon Fluxes, Water Levels, and Related 

Environmental Data, Twitchell Island, 

Sacramento-San Joaquin Delta, California, 

November 1992 through September 1995

By Barry D. Kerr, Bronwen Wang, and Judy Z. Drexler

Prepared in cooperation with the

CALIFORNIA DEPARTMENT OF WATER RESOURCES

Sacramento, California

2003

Open-File Report 03-370

U.S. GEOLOGICAL SURVEY 6217–72
For additional information write to:

District Chief

U.S. Geological Survey

Placer Hall, Suite 2012

6000 J Street

Sacramento, CA 95819-6129

http://ca.water.usgs.gov

We would like to acknowledge the efforts and contribution of our field crew: Susan Bird, Michael 

Hunerlach, and Francis Huber.

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does 

not imply endorsement by the U.S. Government.

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
Contents iii

CONTENTS

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

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

Description of Wetland Enclosures...................................................................................................................... 3

Methods and Data................................................................................................................................................. 3

Soil Moisture............................................................................................................................................... 3

Soil Percent-Carbon Content and Bulk Density.......................................................................................... 5

Ground-Water Levels.................................................................................................................................. 5

Elevation Measurements ............................................................................................................................. 5

Gaseous Carbon-Flux Measurements ......................................................................................................... 6

Biomass Measurements............................................................................................................................... 7

Summary .............................................................................................................................................................. 7

References Cited .................................................................................................................................................. 7

Tables ................................................................................................................................................................... 9
iv Figures

FIGURES

Figure 1. Map showing location of the study site, Twitchell Island, Sacramento-San Joaquin Delta, 

California ........................................................................................................................................... 2

Figure 2. Diagram of ponds, control sites, and extensometer, Twitchell Island, California............................. 4
Tables v

TABLES

Table 1. Moisture content of soil cores collected at pond S, Twitchell Island, California ................................. 9

Table 2. Moisture content of soil cores collected at control site SM, Twitchell Island, California.................... 10

Table 3. Moisture content of soil cores collected at pond M, Twitchell Island, California................................ 11

Table 4. Moisture content of soil cores collected at control site MF, Twitchell Island, California.................... 12

Table 5. Bulk density and percent carbon content of soil on July 26, 1993, Twitchell Island, California ......... 13

Table 6. Daily mean water levels at pond S, 1993, Twitchell Island, California................................................ 14

Table 7. Daily mean water levels at pond S, 1994, Twitchell Island, California................................................ 15

Table 8. Daily mean water levels at pond S, 1995, Twitchell Island, California................................................ 16

Table 9. Daily mean water levels at pond M, 1993, Twitchell Island, California .............................................. 17

Table 10. Daily mean water levels at pond M, 1994, Twitchell Island, California ............................................ 18

Table 11. Daily mean water levels at pond M, 1995, Twitchell Island, California ............................................ 19

Table 12. Daily mean water levels at pond F, 1993, Twitchell Island, California.............................................. 20

Table 13. Daily mean water levels at pond F, 1994, Twitchell Island, California.............................................. 21

Table 14. Daily mean water levels at pond F, 1995, Twitchell Island, California.............................................. 22

Table 15. Daily mean water levels at the extensometer, 1993, Twitchell Island, California.............................. 23

Table 16. Daily mean water levels at the extensometer, 1994, Twitchell Island, California.............................. 24

Table 17. Daily mean water levels at the extensometer, 1995, Twitchell Island, California.............................. 25

Table 18. Mean spirit levels at pond S, Twitchell Island, California.................................................................. 26

Table 19. Mean spirit levels at pond M, Twitchell Island, California ................................................................ 27

Table 20. Mean spirit levels at pond F, Twitchell Island, California.................................................................. 28

Table 21. Mean spirit levels at the control sites and extensometer, Twitchell Island, California ...................... 29

Table 22. Daily mean elevation change relative to established datum as measured by extensometer, 1993, 

Twitchell Island, California ............................................................................................................... 30

Table 23. Daily mean elevation change relative to established datum as measured by extensometer, 1994, 

Twitchell Island, California ............................................................................................................... 31

Table 24. Daily mean elevation change relative to established datum as measured by extensometer, 1995, 

Twitchell Island, California ............................................................................................................... 32

Table 25. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site S1, Twitchell Island, California ............................ 33

Table 26. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site S2, Twitchell Island, California ............................ 34

Table 27. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site S3, Twitchell Island, California ............................ 35

Table 28. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at control site SM, Twitchell Island, California ....................... 36

Table 29. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site M1, Twitchell Island, California........................... 38

Table 30. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site M2, Twitchell Island, California........................... 40

Table 31. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site M3, Twitchell Island, California........................... 42

Table 32. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at control site MF, Twitchell Island, California ....................... 44

Table 33. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site F1, Twitchell Island, California ............................ 46

Table 34. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, 

and adjusted R2 for flux regression at pond site F2, Twitchell Island, California ............................ 47
vi Tables

Table 35. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes,

and adjusted R2 for flux regression at pond site F3, Twitchell Island, California ............................ 48

Table 36. Biomass measurements based on vegetation sampling on October 13, 1993, Twitchell Island, 

California ........................................................................................................................................... 49

Table 37. Biomass measurements based on vegetation sampling on October 25, 1994, Twitchell Island, 

California ........................................................................................................................................... 50

Table 38. Biomass measurements based on vegetation sampling on July 25, 1995 (pond S), and October 31, 

1995 (ponds M and F), Twitchell Island, California ......................................................................... 50
Conversion Factors, Definitions, and Achnowledgment vii

CONVERSION FACTORS, DEFINITIONS, AND ACKNOWLEDGMENT

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

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.

Water year: the 12-month period October 1 to September 30. The water year is designated by the calendar year in which it 

ends and which includes 9 of the 12 months. For example, the year ending Sepember 30, 1993, is called the "1993 water 

year." In this report, unless specified otherwise, "years" refer to water years.

ABBREVIATIONS:

CO2, carbon dioxide

CH4, methane

g/cm2, gram per square centimeter

gC/m2/day, grams carbon per square meter per day

WELL NUMBERING SYSTEM

The well-numbering system used by the U.S. Geological Survey (USGS) and the State of California designates the location 

of wells according to the rectangular system for the subdivision of public lands (Bader, 1969). Well identification consists of

a township number, north or south; the range number, east or west; and the section number. Each section is further divided 

into sixteen 40-acre tracts lettered consecutively (except I and O), beginning with A in the northeast corner of the section and 

progressing in a sinusoidal manner to R in the southeast corner. Within each 40-acrea tract, wells are sequentially numbered 

in the order in which they are inventoried. The final letter in a well identification number refers to the base line and meridian. 

Wells in this study area are referenced to the Mount Diablo base line and Meridian (M). 

The station identification number used by the USGS for wells is principally for correlation and retrieval of computerized 

data and is not considered a State location number. The Twitchell Island extensometer number is 380544121403301 (latitude 

38o05'44", longitude 121o40'33", sequence 01), and the water-level well numbers are 380544121403302 for pond F, 

380544121403303 for pond M, and 380544121403304 for pond S.

Multiply By To obtain

acre 0.4047 square hectometer

centimeter 0.06102 inch

cubic meter (m3) 264.2 gallon 

foot (ft) 0.3048 meter

gram (g) 0.03527 ounce avoirdupois

inch (in.) 2.540 centimeter

kilogram (kg) 2.205 pound avoirdupois

kilogram per cubic meter (kg/m3) 16.02 pound per cubic foot

liter (L) 0.2642 gallon 

meter (m) 3.281 foot 

mile (mi) 1.609 kilometer

square inch (in2) 6.452 square centimeter

square mile (mi2) 2.590 square kilometer
Introduction 1

Carbon Fluxes, Water Levels, and Related Environmental 

Data, Twitchell Island, Sacramento-San Joaquin Delta, 

California, November 1992 through September 1995

By Barry D. Kerr, Bronwen Wang, and Judy Z. Drexler

ABSTRACT

Most of the Sacramento-San Joaquin Delta was 

leveed, drained, and converted to agricultural use by 

the 1930s. Land-surface elevations have since subsided 

by more than 20 feet in some areas. Subsidence 

increases the likelihood of levee failure and flooding, 

which, in turn, jeopardizes water delivery and water 

quality in the Delta. This is of major concern because 

the Delta supplies water to two-thirds of California. 

Previous research has shown that oxidation of peat 

soils is the primary cause of subsidence in the Delta. 

Therefore, a possible strategy for remedying this 

situation is to convert drained agricultural fields back to 

wetlands, which are flooded at least part of the year. 

Rehabilitation of wetlands would promote the growth 

of peat, thereby mitigating and possibly reversing 

subsidence. 

This report describes a study that evaluated this 

strategy. In three experimental enclosures or ponds, 

carbon inputs were measured in the form of plant 

biomass and outputs in the form of carbon dioxide 

(CO2) and methane (CH4) fluxes. Each of the ponds 

received one of the following water treatments: 

seasonally flooded, seasonally flooded and irrigated, or 

permanently flooded. Land-surface elevation, groundwater levels, and soil and air temperature also were 

measured. This report presents the data collected 

during the initial phase of the study, which ran from 

November 1992 through September 1995.

INTRODUCTION

The Sacramento-San Joaquin Delta is located at 

the confluence of the Sacramento and San Joaquin 

Rivers, at the eastern end of the Suisun Bay, California 

(fig. 1). The Delta includes more than 1,000 mi2, and 

was once tidal marshland (Atwater, 1980). From 1867 

through the 1930s, 2,250 mi of levees were built 

(Gilbert, 1917). This resulted in the formation of about 

100 islands that are used primarily for agriculture.

Agricultural land in the Delta has undergone 

significant subsidence since drainage. Prokopovitch 

(1985) reported subsidence rates in the Delta between 

0.092 to 0.384 ft/yr. Some of the islands in the central 

Delta are now more than 20 ft below sea level as a 

result of land subsidence. Causes of subsidence include 

oxidation of soil organic matter, mechanical 

compaction, wind erosion, anaerobic decomposition, 

and dissolution by ground water of soil organic matter 

(Weir, 1950; Armentano, 1980; Stephens and others, 

1984; Prokopovitch, 1985). Rojstaczer and others 

(1991) showed that subsidence due to ground-water 

withdrawals and natural-gas extraction are not the 

primary causes of subsidence in the Delta. Rather, 

subsidence in the Delta is chiefly due to oxidation of 

organic peat soils subsequent to drainage for 

agriculture (Deverel and Rojstaczer, 1996). 
2 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Figure 1. Map showing location of the study site, Twitchell Island, Sacramento-San Joaquin Delta, California.
Description of Wetland Enclosures 3

Subsidence is of major concern to the regional 

ecosystem, economy, and water distribution system 

because it increases the risk of levee failure. Levee 

integrity is threatened due to the increasing hydraulic 

gradient between water levels in the rivers and water 

levels on the islands, as well as possible seismic 

activity. The Delta is the transfer point for the majority 

of the water exported to southern California, where it is 

used for industrial purposes, irrigation, and domestic 

consumption. If levees failed in the Delta, the resulting 

upstream movement of brackish water from the San 

Francisco Bay could cause significant water-quality 

and usage problems, especially during a period of low 

river flow (Hundley, 1992).

A possible approach for subsidence mitigation 

involves flooding agricultural lands, thereby restoring 

wetlands and minimizing peat oxidation. The purpose 

of this project was to test this mitigation strategy in 

experimental enclosures that contained miniature 

wetland ecosystems. Each enclosure or pond received a 

different hydrologic treatment. The treatments included 

seasonally flooded (S for seasonal), seasonally flooded 

with subsequent irrigation (M for moist), and 

permanently flooded to a depth of about 14 inches (F 

for flooded). This report presents the preliminary data 

collected on Twitchell Island from November 1992 

through September 1995. The data collected include 

carbon fluxes, water levels, and related environmental 

data.

DESCRIPTION OF WETLAND ENCLOSURES

The three wetland enclosures or ponds were 

situated near the southwestern end of Twitchell Island, 

in the western part of the Sacramento-San Joaquin 

Delta near Rio Vista (fig. 1). Twitchell Island is 

bordered by the San Joaquin River on the south, 

Threemile Slough on the west, and Sevenmile Slough 

on the north and west. The ponds are 32 ft x 32 ft in 

size and were constructed with 3.7 ft x 3.7 ft sheets of 

marine grade 3/4-inch plywood. The sheets were 

buried about 1 ft into the soil with the remaining 2.7 ft

above ground. The plywood sheets were joined 

together using galvanized steel brackets with attached 

pipes that extend into the soil for additional stability. 

Heavy black plastic was used to line the inside of the 

walls and extend approximately 3 ft into the soil. Each 

pond was equipped with an elevated walkway to 

facilitate measurements without disturbing the 

sampling sites. Each pond contained an observation 

well for ground-water level measurements; eight 

elevation points for measuring land-surface elevations 

(spirit leveling); three permanently installed, flux 

chambers for measuring CO2 and CH4 fluxes; and a 

neutron-probe access tube for measuring soil moisture 

(fig. 2). 

Pond S was seasonally flooded from early fall 

through winter and was drained during the spring and 

summer. Pond M was seasonally flooded, similarly to 

pond S; however, it was irrigated in June and August. 

Pond F was permanently flooded. Additionally, control 

sites that received no hydrologic treatments were 

established between ponds S and M (control site SM) 

and between ponds M and F (control site MF) (fig. 2). 

Each control site was equipped with a flux chamber, an 

elevation point, and a neutron-probe access tube. 

An extensometer—an instrument that measures 

land-surface subsidence—and a water-table well were 

installed 60 ft east of the ponds. Data collected from 

this part of the site include land-surface elevation, 

ground-water level, and ground-water temperature. 

The station identification number used by the 

USGS for wells is principally for correlation and 

retrieval of computerized data and is not considered a 

State location number. The Twitchell Island 

extensometer number is 380544121403301 (latitude 

38o05'44", longitude 121o40'33", sequence number 

01), and the water-level-well numbers are 

380544121403302 for the well in pond F, 

380544121403303 for pond M, and 380544121403304 

for pond S.
4 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

pond S pond M

pond M

pond F

control site SM

control site MF water

tank

well

NOT TO SCALE

N

catwalk

CO2 and CH4 flux chambers

123

leveling points

M1L M1H M2L M3L M4L M2H M3H M4H

extensometer

plank

Figure 2. Diagram of ponds, control sites, and extensometer, Twitchell Island, California.
Methods and Data 5

METHODS AND DATA

Soil Moisture

Soil cores were collected in July 1993 (when the 

neutron-probe access tubes were installed) at 0.5 ft 

intervals from 0.5 ft to 3.5 ft in depth. Cores were 

collected from each pond (S, M, and F) and at one of 

the two control sites (SM). Due to the high moisture 

content, it was impossible to collect soil cores at the 

second control site (MF). Soil-moisture content 

(kilograms of water per cubic meter of soil) was 

determined in the laboratory, using methods described 

by Bell and McCulloch (1983). A Troxler 3332 neutron 

moisture probe was used, concurrent with flux 

measurements, to measure soil-moisture content. 

Because soils consist of various materials other than 

water that contain hydrogen (and hydrogen is the key 

element involved in neutron-probe measurements), the 

gage must be calibrated in the field for individual soils 

(Troxler, 1983). A 4-minute standard count was made 

at the beginning of the measurement session and was 

used for all calculations for that day. One-minute 

measured counts were taken at 0.5-ft intervals from 0.5 

ft to 3.5 ft in depth. The ratios of the measured counts 

of the neutron moisture probe at each of the different 

depths divided by the standard count were regressed as 

a third order polynomial with the volumetric soilmoisture values obtained in the lab (Troxler, 1983). We 

used regression equations to estimate soil volumetric 

moisture contents from the measured-count/standardcount ratios. Tables 1-4 present the data for soilmoisture content in kilograms per cubic meter at 0.5-ft 

depth intervals from 0.5 ft to 3.5 ft in depth, for the 

period from July 26, 1993, to July 14, 1995.

Soil Percent-Carbon Content and Bulk Density

Percent soil organic matter was determined by 

loss on ignition as described by Nelson and Sommers 

(1982). Soil bulk density was determined by the core 

method described by Blake and Hartge (1986) at each 

neutron-probe site except for control site MF. Because 

of the lack of cores at control site MF, the means of 

bulk density measurements at the other four sites were 

used to estimate the soil-moisture content for this site. 

This was necessary because volumetric moisture 

content is the product of bulk density and gravimetric 

moisture content. Gravimetric moisture is the weight of 

the water in a sample divided by the weight of the dry 

soil. Without an estimate of bulk densities for site MF, 

calculation of volumetric moisture contents for this site 

would not have been possible.

Table 5 presents bulk density and percent soil 

organic matter for the soil cores taken on July 26, 1993, 

at depths of about 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 ft.

Ground-Water Levels

Observation wells were 10 ft deep and were 

constructed of 2-in. outside diameter (OD) PVC pipe. 

Pipes were inserted 8 ft deep into hand-augured 

boreholes. The bottom 2.5 ft of PVC pipe in the ground 

was 2-in. diameter slotted (0.020-in. openings) PVC 

pipe with an end cap. The screened intervals were from 

about 5.5 ft to 8 ft below land surface. Soil removed 

from the boreholes was used to fill the annular space in 

the observation wells. Shaft encoders equipped with 

floats and counter-weights connected by stainless-steel 

tapes measured water levels hourly in the three ponds. 

The tapes have holes every 0.2 ft and match the shaft 

encoder pulleys. The shaft encoders have a resolution 

of 0.01 ft. All three ponds shared an automatic data 

recorder, which was powered by a battery and a solar 

panel. The extensometer well was equipped with a 

submersible pressure transducer, which measured 

water levels every hour. 

Data from the automatic data recorders were 

retrieved from the sites on a monthly basis and 

uploaded to the USGS's Automated Data Processing 

System (ADAPS). Hand-held water-level 

measurements were made monthly as a quality control 

check. These were done with a steel tape in accordance 

with standard USGS field procedures (U.S. Geological 

Survey, 1977). Linear interpolations of corrections of 

digital data for shaft encoder and submersible pressure 

transducer drift were computed using any differences 

between the steel tape water-level measurements and 

the automatic data recorder values stored in ADAPS.

The daily mean ground-water levels for ponds S, 

M, and F are presented in tables 6-8, 9-11, and 12-14, 

respectively. The daily mean ground-water levels for 

the extensometer are presented in tables 15-17. These 

are the output data from the USGS ADAPS database 

and are the mean depth below land surface.
6 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Elevation Measurements

Shallow, land-surface elevation changes were 

measured using an extensometer. This instrument 

consisted of three steel pipes supporting an instrument 

table that was lodged in concrete below the organic soil 

(approximately 10 ft deep). A linear variable 

differential transformer (LVDT) was mounted to the 

instrument table with nonferrous connectors. 

Measurements were generated by a rod extending from 

the LVDT and resting on an aluminum plate (0.24 in. 

thick and 16 in. square) that was flush with the land 

surface. The LVDT responded to slight upward or 

downward movements by registering a voltage. Data 

from the LVDT and ground-water well were sent 

hourly to a data logger. Dial-gage readings were made 

during monthly data retrievals, and the distance 

between the plate and the support structure was 

recorded as a quality-control check. The LVDT output, 

in millivolts, was converted in ADAPS to feet of landsurface subsidence relative to an arbitrary benchmark.

Spirit-level surveys were conducted periodically 

at eight sites within each pond, the two control sites, 

the plate at the top of the extensometer, the support 

table, and one benchmark. The eight leveling points in 

each pond were grouped in pairs, one “high” and one 

“low,” and the pairs were evenly spaced along the south 

side of the catwalks (fig. 2). The “low” measuring 

points were plastic disks 3.25 in. in diameter with 

equilateral triangles cemented on top to form an open 

pyramid shape, and were about 0.104 ft above land 

surface. The “highs” were about 3.00 ft above land 

surface and were 1 in. OD PVC pipe sections that 

rested on top of 3.25 in. plastic bases. The benchmark 

has an elevation of -5.977 ft below sea level, the 

measuring point of which is about 1.62 ft above land 

surface. Duplicate readings were made to 0.001 ft, and 

these stadia-rod data were converted to average 

elevation values using the Statistical Analysis System 

(SAS Institute Inc., 1990). 

Tables 18-21 present the spirit-level averages for 

each measuring date for ponds S, M, F and the control 

sites and extensometer, respectively. The values are 

actual elevations in feet below sea level of the 

measuring points (NGVD). As stated above, the “low” 

leveling points were about 0.104 ft above the actual 

ground surface and the “high” leveling points were 

about 3.00 ft above the actual ground surface. 

The daily mean LVDT levels for the 

extensometer site are presented in tables 22-24. These 

are the output data from the USGS ADAPS database 

and represent the mean land-surface subsidence 

relative to the established datum.

Gaseous Carbon-Flux Measurements

The closed static-flux chambers and the methods 

used to collect gaseous carbon samples for flux 

determinations are described by Deverel and others 

(1998). Three stainless-steel flux-chamber bases were 

pressed into the soil and left in place for the duration of 

the study in each pond and control site. When the sites 

had no standing water, water was poured into the base 

collars to provide a seal between the flux chambers and 

the bases. Flux-chamber tops were Mylar balloons, 

which were affixed with PVC collars at the start of 

each flux sampling. Each flux chamber had a gassampling tube affixed, which was purged prior to each 

sample. Flux chambers were fitted with thermocouples, 

so that flux-chamber temperatures could be recorded 

each time a sample was withdrawn. This allowed for 

ideal gas law corrections to be made to flux 

calculations. The flux chambers were left in the field 

with their collars removed between flux measurements 

to allow open exchange with the atmosphere. The fluxchamber sites were shaded with umbrellas and (or) 

tarps for a half-hour prior to the start of each chamber 

flux sampling to minimize the effects of 

photosynthesis. Samples were withdrawn at time zero 

and at equal intervals, usually 5 minutes apart, up to 20 

minutes duration. Gas samples were collected in glass 

syringes equipped with Teflon Mininert valves that 

were closed after sampling. Soil temperatures were 

measured at depths of 4 and 12 in. at the conclusion of 

each flux-chamber sampling with an Omega digital 

thermometer model 450-AKT equipped with a 1-ftlong stainless-steel penetration thermocouple probe 

type K. The distance from the ground to the top of the 

flux chamber and the distance from any standing water 

in the flux-chamber base to the top of the flux chamber 

were recorded. The flux-chamber headspace volume 

was calculated from these measurements and used in 

the flux calculations. The CO2 and CH4 fluxes are 

reported as grams of carbon per square meter per day.

Samples were analyzed immediately in the field 

by gas chromatography (GC). Carbon dioxide was 

analyzed with a Microsensor Technology Inc. M200 
References Cited 7

gas chromatograph (GC) with a 10 in. x 0.02 in. ID 

HayeSep A column at 55 οC with a thermal 

conductivity detector. The GC was equipped with a 

sample vacuum pump and had an internal solid-state 

10-microliter sample loop. CH4 was analyzed with an 

Hnu model 301 GC equipped with a 6 ft x 1/8 in. OD 

Porapak T column at 60 οC, a flame ionization detector 

at 150 οC, and an exterior sample loop of 0.5 ml. 

Helium was the carrier gas for both GCs. Peak heights 

(CO2) and peak areas (CH4) were determined 

electronically and were regressed against known 

concentrations of CO2/CH4 combined standard gases 

mixed with nitrogen (Intermountain Specialty Gas, 

Nampa, Idaho). Standard concentrations of CO2 were 

321, 385, 741, 1,136, and 2,490 parts per million 

(ppm); standard concentrations of CH4 were 1.1, 10, 

34, 60.8, and 105 ppm. Standard linear regressions 

were used for the calibration of CO2 and second order 

polynomial regressions for CH4.

A quality-control (QC) sample of known 

concentration was included in each flux-chamber 

sampling and compared in the field with the standard 

peak for that concentration. QC samples deviating 

more than 10 percent from standards triggered a 

recalibration. Recalibrations were done after every 

three samplings regardless of the QC results.

Tables 25-35 present the CO2 and CH4 fluxes for 

sites S1, S2, S3, SM, M1, M2, M3, MF, F1, F2, and F3. 

In addition to the CO2 and CH4 fluxes, the average 

flux-chamber temperature, soil temperature at a depth 

of 1 ft, water depth in the flux chamber, the headspace, 

and the adjusted coefficient of determination for the 

CO2 and CH4 concentrations over time are listed by 

date.

Biomass Measurements

Above-ground plant biomass samples were 

collected from randomly chosen 2-ft x 2-ft plots within 

each pond. These plots were delineated with wooden 

stakes and string. The vegetation was cut with shears 

below the string to ground level. All collected 

vegetation was placed in paper bags that previously had 

been weighed and labeled. The samples were dried for 

48 hours at 65 οC, ground, weighed, and analyzed for 

carbon content with a Perkin-Elmer Series II CHNS/O 

Analyzer model 2400. Table 36 shows the data from 

samples collected on October 13, 1993. Table 37 shows 

the data from samples collected on October 25, 1994. 

The data from samples collected on July 25, 1995, in 

pond S and on October 31, 1995, in ponds M and F are 

shown in table 38.

SUMMARY

Wetland enclosures were used to evaluate 

whether the act of restoring wetlands can mitigate and 

possibly reverse land-surface subsidence of peat. Three 

hydrologic treatments were tested to determine whether 

water management could significantly reduce carbon 

fluxes. The treatments were seasonally flooded, 

seasonally flooded and irrigated, and permanently 

flooded. Data for soil-moisture content, soil 

temperature, water level, land-surface elevation, carbon 

outputs (in the form of CO2 and CH4 fluxes), and 

carbon inputs (in the form of plant biomass) are 

presented in this report.

REFERENCES CITED

Armentano, T.V., 1980, Drainage of organic soils as a factor 

in the world carbon cycle: BioScience, v. 30, no. 12, 

p. 825-830.

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climatic records between San Francisco Bay, the 

Sacramento-San Joaquin Delta, and the Mokelumne 

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Eighteenth Biennial Conference on Ground Water—

Changing practices in ground water management; the 

pros and cons of regulation: Water Resources Center, 

University of California Riverside, Report No. 77, 

p. 62-74.

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A., ed., Methods of Soil Analysis, Part 1, Agron. 

Monogr., v. 9: American Society of Agronomy and Soil 

Science Society of America, Madison, Wis., p. 363-

375.
8 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

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agricultural lands in the Sacramento-San Joaquin Delta, 

California—Role of aqueous and gaseous carbon 

fluxes: Water Resources Research, v. 32, no. 8, p. 2359-

2367.

Deverel, S.J., Wang, B., and Rojstaczer, S., 1998, 

Subsidence of organic soils, Sacramento-San Joaquin 

delta, California, in Borchers, J.W., ed., Land 

subsidence case studies and current research—

Proceedings of the Dr. Joseph F. Poland Symposium: 

Association of Engineering Geologists, p. 489-502.

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Nevada: U.S. Geological Survey Professional Paper 

105, 154 p. 

Hundley, N.H., Jr., 1992, The great thirst—Californians and 

water, 1770s-1990s: Berkeley, University of California 

Press, 551 p.

Nelson, D.W., and Sommers, C.E., 1982, Total carbon, 

organic carbon, and organic matter, in Page, A.L., ed., 

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C.A., 1991, Evaluation of selected data to assess the 

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Tables 9

Table 1. Moisture content of soil cores collected at pond S, Twitchell Island, California

[Missing data are denoted as —]

Date

Moisture content, in kilograms per cubic meter

0.5 feet 1.0 feet 1.5 feet 2.0 feet 2.5 feet 3.0 feet 3.5 feet

7/26/93 153.18 378.28 627.56 839.39 892.00 902.90 912.85

7/28/93 148.97 365.66 628.57 850.39 870.94 890.08 896.15

8/12/93 141.97 361.92 623.90 821.44 866.73 891.48 909.23

8/23/93 146.23 360.94 627.92 817.67 881.24 891.59 907.60

9/8/93 147.72 376.07 636.75 857.52 890.76 888.86 906.42

9/21/93 150.73 369.08 640.15 844.97 847.30 869.70 884.16

9/27/93 141.54 371.40 825.52 850.18 866.47 862.74 880.89

10/6/93 166.69 383.35 648.43 858.51 878.72 878.72 902.69

11/5/93 469.17 608.20 669.47 833.48 873.07 883.44 898.99

11/18/93 501.90 608.70 652.16 819.54 868.08 867.16 881.95

11/30/93 502.49 601.54 651.29 815.75 857.22 858.60 880.25

2/23/94 560.68 608.90 659.90 824.01 864.81 863.88 875.47

3/4/94 578.99 603.23 712.77 847.49 867.00 867.07 885.25

3/16/94 562.01 584.66 704.87 837.10 858.83 856.52 880.57

4/11/94 519.42 578.30 718.31 856.93 859.25 859.25 871.30

4/29/94 373.57 513.75 726.59 867.70 857.92 856.99 876.08

5/11/94 423.67 549.27 722.39 864.92 864.45 866.34 889.39

5/20/94 391.74 525.79 724.52 873.57 865.13 871.69 884.82

6/27/94 241.65 457.16 714.92 850.54 858.90 861.69 874.23

7/14/94 244.44 450.95 — — — — —

7/27/94 234.07 455.09 708.43 812.38 859.68 864.36 878.88

8/22/94 232.37 449.79 692.41 854.77 860.37 858.04 881.37

9/8/94 238.44 436.26 686.34 849.64 852.90 851.04 882.76

10/26/94 256.81 451.35 694.06 829.31 856.64 847.84 865.90

4/12/95 583.57 605.90 704.54 840.88 857.16 852.97 880.42

4/17/95 615.92 602.93 691.56 804.32 849.33 856.75 866.50

5/17/95 615.93 605.60 719.70 847.42 868.55 864.79 886.86

6/28/95 397.58 555.82 716.41 855.87 856.34 860.57 887.33

7/14/95 260.58 452.05 712.16 848.99 855.99 854.59 884.48

TABLES
10 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 2. Moisture content of soil cores collected at control site SM, Twitchell Island, California

[Missing data are denoted as —]

Date Moisture content, in kilograms per cubic meter

0.5 feet 1.0 feet 1.5 feet 2.0 feet 2.5 feet 3.0 feet 3.5 feet

7/26/93 179.59 400.82 640.19 801.12 835.58 841.92 863.23

7/27/93 170.38 400.01 633.27 811.27 831.65 835.72 848.41

7/28/93 171.83 393.41 633.75 802.61 802.16 820.92 830.31

7/29/93 168.48 392.00 628.82 786.26 815.97 828.39 841.25

7/30/93 171.94 396.74 652.56 795.53 813.51 836.44 856.22

7/31/93 173.98 400.34 648.56 792.02 831.19 849.41 919.55

8/2/93 178.83 394.84 653.14 802.55 822.35 841.25 861.05

8/4/93 170.28 398.89 653.14 791.30 804.80 828.65 855.65

8/12/93 169.15 392.96 637.32 782.51 795.01 823.60 844.60

8/23/93 169.52 406.45 642.47 792.01 791.11 832.10 849.66

9/7/93 177.31 414.12 664.18 795.84 799.50 826.93 852.98

9/8/93 169.45 414.71 650.43 796.22 801.67 832.56 852.09

9/10/93 173.84 417.51 661.64 797.31 805.03 819.09 854.94

9/13/93 174.46 411.79 659.08 783.18 794.06 835.72 852.94

9/15/93 160.45 411.26 635.39 780.80 784.80 815.49 837.72

9/21/93 171.69 419.40 647.47 784.04 791.18 818.40 840.72

9/27/93 176.61 196.19 648.41 781.50 790.84 809.98 831.35

10/6/93 194.87 421.91 656.15 798.23 783.39 822.95 837.34

10/21/93 219.48 493.43 662.02 789.35 783.52 811.32 852.12

10/22/93 205.91 523.73 650.69 780.75 774.53 816.26 834.01

10/25/93 212.31 549.93 660.22 786.66 790.70 820.74 842.26

10/27/93 236.49 553.56 668.74 782.14 788.36 801.26 830.16

10/29/93 218.41 542.75 657.07 772.27 770.50 804.17 836.96

11/1/93 239.66 560.24 658.43 788.01 793.83 813.56 842.71

11/5/93 250.37 565.50 650.71 786.86 797.68 817.97 836.91

11/18/93 402.92 571.43 643.08 780.63 784.61 809.38 829.29

11/30/93 455.29 567.23 644.35 784.05 791.10 807.41 825.03

2/23/94 540.13 580.48 649.22 789.37 814.20 815.97 827.51

3/4/94 548.79 572.87 652.69 810.98 819.01 820.35 832.83

3/16/94 494.03 576.30 652.37 781.08 801.42 819.11 831.50

4/11/94 416.39 572.06 654.99 802.23 805.77 809.32 819.52

4/29/94 315.75 453.41 661.91 795.11 801.80 820.51 824.07

5/11/94 348.94 482.59 667.54 800.75 815.15 825.95 834.05

5/20/94 340.99 480.43 657.98 801.46 811.32 831.05 844.95

6/22/94 245.73 428.04 669.04 796.26 799.39 829.41 833.89

6/23/94 239.64 412.32 648.02 785.18 793.17 824.25 824.25

6/24/94 248.65 417.82 651.44 802.26 803.15 827.32 831.35

6/27/94 250.07 422.01 656.15 772.55 762.78 805.43 832.53

6/29/94 240.59 416.92 665.76 769.14 794.20 814.79 829.56

7/1/94 242.82 428.86 670.26 780.07 767.36 830.44 839.97

7/27/94 239.90 420.88 655.60 771.62 755.05 823.13 831.65

8/15/94 224.20 424.64 668.29 803.91 815.87 838.39 843.45

8/16/94 222.29 411.12 672.79 779.34 803.17 826.55 835.09

8/17/94 220.28 422.36 658.35 779.05 803.47 835.57 835.11

8/22/94 212.75 412.70 653.71 780.91 779.58 815.28 829.56

9/8/94 210.07 410.47 648.80 776.90 801.00 820.19 813.94

10/26/94 206.89 427.11 645.55 782.90 788.67 801.96 825.00

4/6/95 540.45 595.49 — — — — —

4/12/95 522.00 588.32 651.53 800.64 812.21 821.56 822.89

4/17/95 520.18 585.88 647.58 790.95 805.16 826.47 821.14

5/17/95 507.79 586.84 676.23 799.31 819.97 824.01 831.20

6/28/95 338.44 504.19 673.98 811.88 824.01 832.54 826.26

7/14/95 301.83 455.95 656.53 790.99 814.67 815.56 813.33
Tables 11

Table 3. Moisture content of soil cores collected at pond M, Twitchell Island, California

Date

Moisture content, in kilograms per cubic meter

0.5 feet 1.0 feet 1.5 feet 2.0 feet 2.5 feet 3.0 feet 3.5 feet

07/26/93 230.44 468.97 684.98 752.95 746.70 764.63 791.32

07/27/93 558.54 576.87 683.53 748.94 743.52 773.52 790.18

07/28/93 471.39 577.41 686.71 740.96 754.93 752.46 780.82

07/29/93 393.03 564.77 679.00 738.96 740.60 744.68 767.11

07/30/93 361.01 552.48 685.65 743.14 748.10 755.13 790.70

07/31/93 365.50 563.67 551.52 693.54 682.65 757.64 756.80

08/02/93 358.42 547.60 686.27 741.32 747.12 765.33 791.41

08/04/93 326.97 536.01 677.16 742.15 745.05 763.68 785.61

08/12/93 293.87 531.80 668.22 729.04 728.22 756.16 786.98

08/23/93 248.94 509.97 674.87 728.32 729.97 746.96 785.91

09/07/93 245.28 494.22 693.97 724.67 743.17 760.41 792.79

09/08/93 602.25 596.82 696.67 729.25 726.33 763.09 789.00

09/10/93 484.83 590.85 690.19 716.49 736.52 747.37 787.86

09/13/93 369.81 580.62 673.53 693.94 728.94 746.02 786.02

09/15/93 341.29 563.00 662.81 678.35 711.07 735.62 765.89

09/21/93 308.40 549.39 666.81 673.79 715.66 747.27 771.09

09/27/93 283.04 528.69 675.27 722.76 712.93 743.64 761.25

10/06/93 282.43 528.08 677.79 722.87 725.35 748.10 778.29

04/29/94 501.70 594.73 674.23 723.81 705.37 742.26 761.93

05/11/94 348.90 579.06 677.99 692.89 722.28 741.74 776.92

05/20/94 329.12 555.13 676.80 685.05 712.68 735.78 769.60

06/20/94 214.93 442.58 680.12 720.05 706.88 739.81 767.39

06/22/94 448.33 569.47 686.08 726.47 717.81 734.29 772.20

06/23/94 411.74 563.23 680.82 722.47 708.18 737.17 769.02

06/24/94 371.37 551.27 686.71 722.11 708.94 742.69 769.04

06/27/94 287.46 496.70 683.88 676.11 701.45 730.47 761.12

06/29/94 264.74 478.81 681.77 719.64 713.88 739.40 771.92

07/01/94 253.18 464.80 688.10 725.25 728.59 741.53 781.18

07/27/94 220.47 449.16 681.55 725.23 712.87 737.18 777.15

08/15/94 227.12 454.21 691.45 742.19 727.81 747.69 789.13

08/16/94 545.87 571.09 682.76 737.76 717.08 744.38 772.50

08/17/94 451.50 570.01 696.43 734.28 716.39 751.74 773.78

08/22/94 339.60 542.00 668.45 693.08 706.63 739.06 766.16

09/08/94 277.20 480.01 669.68 702.94 703.35 732.08 771.50

10/26/94 283.86 502.32 681.25 691.85 703.67 738.72 759.50

04/17/95 604.88 594.67 660.82 679.60 706.55 735.95 765.75

05/17/95 599.92 599.51 676.77 694.54 709.83 744.95 773.87

06/28/95 523.07 592.48 675.12 691.24 714.79 736.27 768.50

07/14/95 591.38 588.92 680.14 736.44 716.30 733.97 763.97
12 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 4. Moisture content of soil cores collected at control site MF, Twitchell Island, California

[Missing data are denoted as —]

Date Moisture content, in kilograms per cubic meter

0.5 feet 1.0 feet 1.5 feet 2.0 feet 2.5 feet 3.0 feet 3.5 feet

07/26/93 132.12 377.32 709.83 801.22 822.48 838.31 850.98

07/27/93 160.58 413.78 764.48 845.41 869.54 887.53 921.13

07/28/93 150.32 409.39 758.56 833.25 865.46 887.86 906.07

07/29/93 139.22 418.66 750.00 833.88 855.66 894.59 899.68

07/30/93 173.68 447.57 758.57 839.85 855.82 881.66 902.33

07/31/93 173.23 446.88 774.79 856.17 876.16 893.29 918.04

08/02/93 171.93 417.86 771.47 842.95 863.17 883.39 905.96

08/04/93 165.35 430.56 756.43 837.78 872.57 877.75 910.19

08/12/93 157.79 421.06 740.82 828.58 847.25 877.13 891.60

08/23/93 156.06 427.17 751.45 832.41 855.00 882.30 906.77

09/07/93 155.63 420.75 738.42 840.64 857.36 886.50 907.04

09/08/93 158.58 458.05 774.13 835.35 864.77 884.71 915.55

09/10/93 160.83 470.45 773.91 835.07 850.72 881.06 904.77

09/13/93 158.21 465.37 750.75 834.52 856.76 873.80 905.98

09/15/93 144.18 461.55 737.57 818.42 836.55 870.47 875.12

09/21/93 152.07 481.80 746.70 819.92 847.43 862.36 895.00

09/27/93 169.87 330.79 749.85 831.24 855.42 858.21 887.98

10/06/93 175.09 475.76 757.64 829.98 840.79 870.86 898.57

10/21/93 206.53 524.65 764.99 910.70 387.84 877.90 896.64

10/22/93 220.03 535.44 754.37 808.17 829.97 861.98 886.10

10/25/93 208.41 576.65 757.03 818.87 845.11 874.16 896.18

10/27/93 212.49 585.16 757.55 810.06 837.48 862.57 889.52

10/29/93 214.12 565.07 743.33 811.39 836.85 860.46 886.39

11/01/93 221.06 647.87 769.21 830.58 846.04 869.00 893.83

11/05/93 245.22 673.45 759.19 827.97 851.05 875.08 25.22

11/18/93 583.05 685.65 762.83 814.59 837.23 864.96 883.45

11/30/93 625.71 684.19 745.89 810.36 825.10 857.80 889.11

04/11/94 617.46 682.34 757.88 815.81 832.03 868.17 885.78

04/29/94 359.47 554.99 767.73 824.99 843.61 860.83 896.21

05/11/94 215.66 547.65 774.30 828.84 847.65 392.00 888.09

05/20/94 355.99 537.30 775.30 827.30 846.98 861.04 882.59

06/20/94 231.92 454.06 771.59 821.63 840.80 863.72 884.76

06/22/94 232.11 525.13 767.12 828.91 849.04 862.61 901.93

06/23/94 239.51 505.75 771.07 817.45 841.11 860.59 883.31

06/24/94 241.27 492.87 773.46 833.32 851.09 868.86 881.02

06/27/94 232.74 461.16 762.92 820.03 840.92 864.13 885.95

06/29/94 234.73 463.41 766.91 825.84 858.11 860.91 891.78

07/01/94 245.23 476.14 769.16 836.49 855.93 885.33 895.29

07/27/94 233.52 459.60 760.57 833.59 849.04 861.68 893.04

08/15/94 240.91 453.24 766.45 852.92 863.97 892.80 900.00

08/16/94 242.74 580.52 767.97 838.91 851.59 864.28 888.24

08/17/94 243.00 560.45 774.45 828.77 851.92 868.46 900.11

08/22/94 246.75 478.07 740.63 811.99 838.57 864.22 882.88

09/08/94 232.76 452.88 748.10 823.65 845.57 860.03 882.88

10/26/94 325.70 — — — — — —

04/12/95 682.41 689.85 766.12 822.87 836.82 854.96 873.56

04/17/95 669.49 684.79 757.15 823.02 837.40 863.37 887.49

05/17/95 660.74 687.97 778.08 825.49 846.14 860.69 887.45

06/28/95 353.78 532.14 768.23 833.47 848.96 859.29 879.94

07/14/95 324.44 615.72 774.90 831.85 839.78 854.25 885.53
Tables 13

Table 5. Bulk density and percent carbon content of soil on July 26, 1993, Twitchell Island, California

Pond Depth (feet) Bulk density Percent carbon

S 0.50 0.92 12.59

S 1.00 1.00 11.11

S 1.50 1.02 13.13

S 2.08 0.25 76.43

S 2.58 0.22 65.08

S 3.21 0.19 59.47

SM 0.50 0.80 12.25

SM 1.00 0.97 12.73

SM 1.50 0.38 48.61

SM 2.00 0.23 45.63

SM 2.50 0.18 71.83

SM 3.00 0.16 66.75

M 0.39 0.74 15.94

M 0.98 0.91 16.20

M 1.15 0.82 19.64

M 1.57 0.29 22.50

M 2.23 0.14 54.47

M 3.08 No data 76.23

MF 0.50 0.82 No sample

MF 1.00 0.96 No sample

MF 1.50 0.56 No sample

MF 2.00 0.21 No sample

MF 2.50 0.18 No sample

MF 3.00 0.18 No sample
14 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 6. Daily mean water levels at pond S, 1993, Twitchell Island, California

[Missing data are denoted by —. Data collection started on May 11, 1993. Water levels are relative to land surface: Positive values signify measurements that 

are below land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 — — — — — — — — 0.96 1.17 0.91 0.76

2 — — — — — — — — 1.00 1.17 .95 .75

3 — — — — — — — — 1.06 1.17 1.08 .75

4 — — — — — — — — 1.00 1.17 1.10 .72

5 — — — — — — — — .92 1.18 1.09 .64

6 — — — — — — — — .94 1.57 1.05 .62

7 — — — — — — — — .93 1.61 1.01 .68

8 — — — — — — — — .91 1.62 1.00 .67

9 — — — — — — — — .95 1.61 1.01 .66

10 — — — — — — — — .97 1.61 1.04 .68

11 — — — — — — — 0.86 .97 1.60 1.04 .75

12 — — — — — — — .88 1.00 1.60 .99 .78

13 — — — — — — — .88 1.09 1.61 .89 .80

14 — — — — — — — .88 1.13 1.64 .82 .84

15 — — — — — — — .90 1.14 1.64 .77 .80

16 — — — — — — — .93 1.15 1.64 .78 .76

17 — — — — — — — .98 1.16 1.65 .85 .74

18 — — — — — — — 1.03 1.16 1.66 .87 .73

19 — — — — — — — 1.05 1.16 1.67 .88 .71

20 — — — — — — — 1.06 1.17 1.66 .88 .71

21 — — — — — — — 1.09 1.17 1.65 .87 .73

22 — — — — — — — 1.10 1.17 1.64 .87 .71

23 — — — — — — — 1.13 1.17 1.59 .89 .69

24 — — — — — — — 1.15 1.17 1.44 .91 .68

25 — — — — — — — 1.06 1.16 1.32 .92 .66

26 — — — — — — — .98 1.16 1.18 .85 .66

27 — — — — — — — .95 1.16 1.03 .80 .67

28 — — — — — — — .96 1.16 .87 .76 .66

29 — — — — — — — 1.00 1.17 .83 .79 .64

30 — — — — — — — .99 1.17 .88 .84 .69

31 — — — — — — — .93 — .89 .85 —
Tables 15

Table 7. Daily mean water levels at pond S, 1994, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface] 

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

 1 0.78 -0.11 -0.34 -0.46 -0.61 -0.44 -0.10 — 0.48 0.72 1.14 0.93

2 .77 -.30 -.46 -.47 -.58 -.42 -.10 — .51 .72 1.13 .90

3 .75 -.14 -.39 -.51 -.56 -.41 -.09 — .57 .72 1.06 .88

4 .70 -.04 -.36 -.53 -.58 -.38 -.07 — .63 .73 .91 .86

5 .66 -.11 -.32 -.62 -.62 -.37 -.05 — .62 .73 .81 .86

6 .62 -.30 -.25 -.69 -.56 -.35 -.03 — .61 .73 .73 .88

7 .61 -.21 -.21 -.67 -.59 -.32 -.03 — .63 .74 .67 .90

8 .60 -.09 -.19 -.67 -.57 -.31 — — .64 .74 .65 .91

9 .61 -.18 -.21 -.67 -.49 -.31 — — .63 .74 .62 .93

10 .60 -.37 -.24 -.67 -.49 -.31 — — .63 .75 .60 .99

11 .59 -.34 -.31 -.66 -.48 -.30 — — .65 .75 .56 1.05

12 .58 -.27 -.30 -.66 -.45 -.25 — — .65 .75 .59 .98

13 .55 -.18 -.32 -.66 -.45 -.24 — — .66 .76 .74 .99

14 .54 -.08 -.36 -.66 -.46 -.24 — — .67 .76 .76 1.00

15 .50 -.03 -.36 -.66 -.47 -.22 — — .67 .75 .68 .99

16 .47 -.08 -.36 -.66 -.49 -.19 — — .67 .76 .62 1.00

17 .46 -.13 -.36 -.65 -.54 -.17 — .18 .68 .77 .61 1.04

18 .45 -.15 -.36 -.64 -.54 -.20 — .15 .68 .86 .64 1.04

19 .44 -.33 -.36 -.66 -.54 -.17 — .15 .68 .95 .76 1.01

20 .32 -.33 -.36 -.66 -.56 -.14 — .14 .69 .95 .90 1.03

21 .07 -.30 -.41 -.66 -.54 -.13 — .15 .69 .97 .96 1.03

22 -.03 -.27 -.51 -.65 -.50 -.14 — .18 .69 .93 .96 1.04

23 .01 -.20 -.46 -.66 -.56 -.14 — .22 .69 .90 .97 1.03

24 .03 -.15 -.40 -.66 -.65 -.17 — .26 .70 .90 .94 .98

25 -.01 -.14 -.39 -.66 -.60 -.16 — .27 .70 .93 .92 .97

26 -.05 -.14 -.40 -.66 -.55 -.15 — .29 .70 .95 .91 .95

27 -.01 -.15 -.37 -.66 -.52 -.14 — .30 .71 1.02 .87 .91

28 -.03 -.19 -.34 -.66 -.47 -.14 — .33 .71 1.04 .92 .87

29 -.04 -.23 -.34 -.66 — -.12 — .36 .71 1.09 .92 .85

30 -.18 -.27 -.41 -.67 — -.11 — .39 .72 1.15 .90 .84

31 -.07 — -.44 -.66 — -.10 — .42 — 1.15 .92 —
16 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 8. Daily mean water levels at pond S, 1995, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.84 0.20 0.06 0.11 -0.34 -0.31 -0.49 -0.22 0.16 0.20 0.87 0.61

2 .81 .13 .06 -.15 -.34 -.31 -.49 -.22 .15 .19 .90 .63

3 .78 .20 .06 -.19 -.33 -.30 -.49 -.21 .16 .19 1.11 .64

4 .72 .22 .04 -.24 -.33 -.28 -.50 -.20 .17 .19 1.19 .64

5 .64 .18 .02 -.24 -.31 -.29 -.51 -.13 .18 .18 1.08 .65

6 .58 .05 .02 -.24 -.31 -.29 -.52 -.09 .18 .18 .80 .65

7 .54 .06 .04 -.28 -.30 -.30 -.52 -.09 .19 .17 .68 .65

8 .53 .08 -.01 -.30 -.30 -.32 -.53 -.08 .19 .16 .59 .64

9 .52 .09 -.02 -.34 -.29 -.36 -.53 -.09 .20 .15 .38 .65

10 .54 .08 .00 -.42 -.30 -.38 -.54 -.08 .20 .14 .24 .65

11 .58 .10 .03 -.38 -.30 -.39 -.54 -.07 .08 .13 .19 .65

12 .59 .11 .01 -.38 -.31 -.39 -.41 -.06 -.01 .12 .12 .65

13 .58 .15 .01 -.37 -.31 -.40 -.24 -.06 .09 .11 .12 .67

14 .59 .15 .01 -.37 -.32 -.41 -.20 -.06 .20 .10 .13 .66

15 .62 .12 .02 -.38 -.31 -.41 -.21 -.06 .20 .09 .14 .66

16 .65 -.03 .02 -.38 -.31 -.44 -.25 -.05 .20 .08 .16 .66

17 .67 -.07 .03 -.38 -.30 -.44 -.29 -.06 .20 .07 .17 .67

18 .64 .01 .05 -.38 -.30 -.43 -.36 -.05 .21 .07 .18 .84

19 .63 .03 .06 -.36 -.30 -.44 -.37 -.05 .21 .74 .18 .84

20 .64 .03 .01 -.36 -.29 -.44 -.40 -.03 .21 .77 .26 .85

21 .62 .03 -.04 -.36 -.29 -.44 -.40 -.03 .21 .79 .40 .85

22 .59 .04 .00 -.35 -.29 -.52 -.35 -.03 .22 .80 .42 .85

23 .59 .02 .01 -.35 -.30 -.56 -.32 -.03 .23 .81 .59 .85

24 .61 .01 .03 -.35 -.30 -.54 -.30 -.02 .22 .82 .58 .85

25 .59 .00 .05 -.36 -.30 -.54 -.27 -.02 .22 .82 .45 .85

26 .38 .02 .07 -.35 -.30 -.55 -.25 -.02 .23 .79 .44 .85

27 .09 .04 .08 -.35 -.30 -.53 -.24 -.02 .23 .80 .47 .84

28 .18 .04 .02 -.35 -.30 -.50 -.24 .00 .23 .81 .54 .84

29 .17 .05 -.07 -.35 — -.48 -.23 .00 .22 .86 .56 .85

30 .24 .06 -.08 -.35 — -.48 -.22 .00 .21 .86 .57 .85

31 .25 — -.10 -.34 — -.49 — .08 — .87 .57 —
Tables 17

Table 9. Daily mean water levels at pond M, 1993, Twitchell Island, California

[Missing data are denoted by —. Data collection started on May 11, 1993. Water levels are relative to land surface: Positive values signify measurements that 

are below land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 — — — — — — — — 1.03 1.54 0.95 0.90

2 — — — — — — — — 1.07 1.56 .96 .88

3 — — — — — — — — 1.10 1.59 1.02 .88

4 — — — — — — — — 1.08 1.57 1.14 .85

5 — — — — — — — — 1.02 1.57 1.13 .82

6 — — — — — — — — 1.02 1.59 1.09 .81

7 — — — — — — — — 1.01 1.61 1.06 .76

8 — — — — — — — — .99 1.59 1.05 .35

9 — — — — — — — — 1.01 1.58 1.06 .28

10 — — — — — — — — 1.02 1.57 1.07 .47

11 — — — — — — — 0.92 1.02 1.57 1.06 .71

12 — — — — — — — .93 1.05 1.58 1.04 .86

13 — — — — — — — .94 1.09 1.59 .97 .91

14 — — — — — — — .94 1.15 1.60 .92 .93

15 — — — — — — — .95 1.17 1.60 .89 .90

16 — — — — — — — .97 1.19 1.63 .88 .87

17 — — — — — — — 1.02 1.22 1.63 .90 .86

18 — — — — — — — 1.04 1.24 1.63 .93 .85

19 — — — — — — — 1.05 1.26 1.62 .99 .84

20 — — — — — — — 1.07 1.29 1.61 .99 .83

21 — — — — — — — 1.09 1.30 1.61 .97 .85

22 — — — — — — — 1.12 1.34 1.60 .96 .84

23 — — — — — — — 1.15 1.34 1.59 .98 .84

24 — — — — — — — 1.18 1.39 1.57 1.06 .83

25 — — — — — — — 1.10 1.43 1.49 1.08 .81

26 — — — — — — — 1.04 1.44 1.34 1.04 .81

27 — — — — — — — 1.03 1.47 1.11 .97 .81

28 — — — — — — — 1.04 1.49 .89 .93 .79

29 — — — — — — — 1.06 1.51 .89 .93 .78

30 — — — — — — — 1.06 1.53 .94 .95 .82

31 — — — — — — — 1.02 — .95 .94 —
18 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 10. Daily mean water levels at pond M, 1994, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.84 -0.04 -0.24 0-.32 -0.52 0-.58 -0.19 — 0.40 1.11 1.12 1.00

2 .84 -.05 -.26 -.32 -.50 -.57 -.19 — .40 1.13 1.12 1.00

3 .83 -.05 -.27 -.33 -.48 -.57 -.20 — .40 1.15 1.11 .99

4 .79 -.04 -.27 -.34 -.46 -.56 -.19 — .40 1.16 1.08 .98

5 .76 -.03 -.27 -.34 -.45 -.56 -.19 — .40 1.17 1.03 .97

6 .72 -.05 -.25 -.34 -.47 -.54 -.19 — .41 1.18 .97 .98

7 .68 -.05 -.23 -.34 -.52 -.54 -.20 — .41 1.21 .93 1.00

8 .64 -.04 -.23 -.35 -.49 -.52 — — .41 1.26 .92 1.01

9 .62 -.08 -.24 -.35 -.44 -.32 — — .42 1.28 .90 1.01

10 .62 -.20 -.26 -.35 -.45 -.19 — — .42 1.26 .88 1.00

11 .61 -.24 -.30 -.35 -.44 -.18 — — .52 1.21 .84 1.01

12 .58 -.23 -.28 -.34 -.43 -.17 — — .80 1.16 .83 1.01

13 .56 -.21 -.29 -.34 -.43 -.17 — — .81 1.06 .88 1.01

14 .56 -.18 -.31 -.35 -.44 -.16 — — .84 1.01 .90 1.02

15 .52 -.14 -.31 -.35 -.43 -.16 — — .88 .99 .82 1.02

16 .50 -.17 -.30 -.35 -.44 -.15 — — .90 .99 .60 1.02

17 .48 -.19 -.30 -.49 -.46 -.15 — 0.27 .89 .99 .63 1.04

18 .48 -.17 -.31 -.52 -.45 -.16 — .26 .89 1.00 .68 1.04

19 .47 -.18 -.31 -.52 -.46 -.16 — .27 .92 1.00 .76 1.02

20 .34 -.20 -.31 -.53 -.48 -.16 — .28 .97 1.00 .85 1.03

21 .09 -.21 -.31 -.52 -.45 -.16 — .29 .87 1.00 .90 1.04

22 .01 -.21 -.31 -.53 -.44 -.17 — .31 .72 .98 .93 1.05

23 -.01 -.20 -.32 -.57 -.53 -.17 — .34 .80 .96 .95 1.05

24 .00 -.20 -.31 -.58 -.60 -.17 — .36 .88 .96 .96 1.02

25 .02 -.20 -.31 -.58 -.60 -.17 — .37 .91 .97 .96 1.02

26 .02 -.19 -.32 -.57 -.59 -.18 — .38 .94 .99 .95 1.00

27 .00 -.20 -.30 -.57 -.59 -.18 — .40 .99 1.03 .95 .98

28 -.05 -.21 -.29 -.56 -.58 -.18 — .40 1.03 1.06 .96 .95

29 -.05 -.22 -.29 -.54 — -.18 — .40 1.07 1.08 .97 .92

30 -.05 -.24 -.31 -.55 — -.19 — .40 1.10 1.11 .97 .91

31 -.05 — -.31 -.55 — -.19 — .40 — 1.12 .99 —
Tables 19

Table 11. Daily mean water levels at pond M, 1995, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.91 0.03 -0.22 -0.38 -0.44 -0.35 -0.37 -0.20 0.12 0.37 0.59 0.45

2 .90 .04 -.22 -.40 -.43 -.35 -.37 -.19 .13 .39 .59 .45

3 .87 .05 -.23 -.42 -.42 -.34 -.37 -.19 .14 .40 .58 .45

4 .84 .05 -.25 -.43 -.41 -.34 -.36 -.18 .15 .42 .58 .45

5 .77 .04 -.25 -.43 -.40 -.34 -.36 -.18 .16 .43 .58 .45

6 .73 -.03 -.24 -.44 -.39 -.33 -.36 -.17 .17 .45 .57 .45

7 .68 -.04 -.23 -.45 -.39 -.33 -.36 -.16 .17 .46 .57 .45

8 .65 -.04 -.25 -.45 -.37 -.33 -.35 -.15 .18 .48 .60 .45

9 .62 -.06 -.28 -.46 -.37 -.35 -.33 -.15 .19 .49 .59 .45

10 .61 -.10 -.28 -.47 -.37 -.41 -.32 -.15 .20 .50 .53 .45

11 .62 -.10 -.27 -.46 -.37 -.44 -.31 -.15 .20 .52 .53 .45

12 .62 -.10 -.28 -.46 -.37 -.43 -.30 -.15 .21 .53 .52 .45

13 .62 -.05 -.29 -.46 -.37 -.42 -.30 -.14 .22 .55 .52 .45

14 .61 -.03 -.29 -.47 -.36 -.42 -.29 -.14 .23 .56 .52 .45

15 .64 -.05 -.29 -.47 -.41 -.42 -.29 -.14 .23 .58 .52 .45

16 .67 -.07 -.29 -.47 -.42 -.44 -.29 -.13 .24 .59 .51 .45

17 .67 -.10 -.29 -.47 -.42 -.45 -.27 -.09 .25 .61 .52 .45

18 .66 -.09 -.29 -.47 -.41 -.45 -.27 -.02 .26 .62 .51 .45

19 .64 -.07 -.29 -.47 -.41 -.44 -.26 .00 .26 .64 .51 .45

20 .63 -.07 -.31 -.47 -.40 -.45 -.25 .01 .27 .65 .51 .45

21 .62 -.07 -.37 -.47 -.40 -.45 -.25 .02 .28 .64 .50 .45

22 .59 -.06 -.36 -.47 -.39 -.48 -.25 .03 .29 .64 .50 .45

23 .58 -.11 -.37 -.47 -.38 -.51 -.25 .03 .29 .64 .49 .45

24 .57 -.27 -.36 -.48 -.37 -.50 -.24 .05 .30 .63 .49 .45

25 .56 -.27 -.34 -.48 -.37 -.49 -.22 .06 .31 .62 .48 .45

26 .48 -.26 -.33 -.47 -.36 -.48 -.21 .06 .32 .62 .48 .45

27 .22 -.24 -.32 -.46 -.35 -.47 -.21 .06 .32 .62 .47 .45

28 .12 -.23 -.34 -.46 -.35 -.45 -.21 .07 .33 .61 .47 .45

29 .00 -.23 -.36 -.45 — -.40 -.20 .09 .33 .61 .46 .45

30 .02 -.23 -.36 -.45 — -.38 -.20 .10 .35 .60 .46 .45

31 .03 — -.37 -.45 — -.38 — .10 — .60 .45 —
20 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 12. Daily mean water levels at pond F, 1993, Twitchell Island, California

[Missing data are denoted by —. Data collection started on May 11, 1993. Water levels are relative to land surface: Positive values signify measurements that 

are below land surface; negative values signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 — — — — — — — — -0.68 -0.23 -0.23 -0.10

2 — — — — — — — — -.68 -.18 -.17 -.10

3 — — — — — — — — -.68 -.16 -.15 -.10

4 — — — — — — — — -.68 -.14 -.15 -.10

5 — — — — — — — — -.68 -.12 -.15 -.10

6 — — — — — — — — -.68 -.10 -.14 -.11

7 — — — — — — — — -.68 -.08 -.13 -.16

8 — — — — — — — — -.68 -.23 -.11 -.26

9 — — — — — — — — -.68 -.58 -.10 -.24

10 — — — — — — — — -.47 -.46 -.09 -.21

11 — — — — — — — -0.55 -.34 -.37 -.08 -.20

12 — — — — — — — -.59 -.45 -.34 -.08 -.19

13 — — — — — — — -.60 -.43 -.34 -.10 -.18

14 — — — — — — — -.60 -.44 -.33 -.12 -.17

15 — — — — — — — -.61 -.47 -.30 -.12 -.19

16 — — — — — — — -.61 -.44 -.27 -.12 -.20

17 — — — — — — — -.62 -.41 -.21 -.11 -.21

18 — — — — — — — -.63 -.40 -.16 -.11 -.23

19 — — — — — — — -.64 -.42 -.13 -.10 -.24

20 — — — — — — — -.64 -.41 -.11 -.09 -.24

21 — — — — — — — -.64 -.38 -.10 -.09 -.30

22 — — — — — — — -.65 -.37 -.08 -.08 -.40

23 — — — — — — — -.65 -.34 -.06 -.11 -.38

24 — — — — — — — -.65 -.30 -.05 -.18 -.37

25 — — — — — — — -.65 -.28 -.05 -.15 -.36

26 — — — — — — — -.65 -.25 -.17 -.14 -.35

27 — — — — — — — -.65 -.19 -.32 -.12 -.37

28 — — — — — — — -.65 -.17 -.31 -.11 -.41

29 — — — — — — — -.66 -.20 -.29 -.10 -.40

30 — — — — — — — -.67 -.24 -.27 -.09 -.38

31 — — — — — — — -.67 — -.26 -.09 —
Tables 21

Table 13. Daily mean water levels at pond F, 1994, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 -0.37 -0.62 -0.77 -0.89 -0.83 -0.81 — — -0.33 -0.30 -0.19 -0.06

2 -.35 -.62 -.77 -.88 -.83 -.80 — — -.31 -.34 -.17 -.20

3 -.35 -.63 -.77 -.88 -.83 -.80 — — -.25 -.27 -.14 -.41

4 -.34 -.65 -.77 -.88 -.83 -.79 — — -.22 -.23 -.11 -.39

5 -.35 -.66 -.77 -.87 -.83 -.79 — — -.22 -.20 -.09 -.32

6 -.36 -.68 -.76 -.87 -.83 -.78 — — -.32 -.18 -.01 -.25

7 -.36 -.69 -.76 -.86 -.83 -.78 — — -.45 -.15 .06 -.21

8 -.36 -.70 -.76 -.86 -.83 -.77 — — -.43 -.13 .18 -.42

9 -.36 -.71 -.77 -.86 -.83 -.76 — — -.39 -.08 .32 -.78

10 -.36 -.74 -.77 -.85 -.83 -.76 — — -.36 .01 .42 -.71

11 -.36 -.78 -.81 -.85 -.83 -.75 — — -.31 .01 .48 -.63

12 -.36 -.80 -.80 -.85 -.83 -.75 — — -.26 -.14 .31 -.52

13 -.36 -.80 -.81 -.84 -.83 -.74 — — -.24 -.13 -.12 -.42

14 -.37 -.80 -.84 -.84 -.83 -.73 — — -.22 -.18 -.12 -.39

15 -.39 -.80 -.84 -.83 -.84 -.73 — — -.19 -.32 -.22 -.34

16 -.40 -.80 -.84 -.83 -.84 -.71 — — -.17 -.28 -.33 -.32

17 -.51 -.80 -.84 -.83 -.84 -.71 — -0.54 -.16 -.24 -.26 -.24

18 -.52 -.79 -.84 -.82 -.84 -.72 — -.53 -.14 -.25 -.22 -.20

19 -.53 -.79 -.84 -.82 -.84 -.72 — -.51 -.15 -.32 -.18 -.19

20 -.54 -.79 -.84 -.81 -.84 -.73 — -.61 -.26 -.28 -.14 -.16

21 -.55 -.80 -.87 -.81 -.84 -.73 — -.71 -.46 -.25 -.11 -.14

22 -.57 -.80 -.93 -.82 -.84 -.74 — -.69 -.46 -.22 -.21 -.14

23 -.57 -.78 -.92 -.82 -.84 -.74 — -.66 -.42 -.20 -.42 -.13

24 -.57 -.78 -.92 -.82 -.84 -.75 — -.61 -.37 -.18 -.38 -.12

25 -.58 -.78 -.91 -.82 -.83 -.75 — -.53 -.32 -.14 -.32 -.11

26 -.58 -.77 -.91 -.82 -.82 -.76 — -.45 -.25 -.11 -.26 -.10

27 -.58 -.77 -.91 -.82 -.82 -.76 — -.43 -.32 -.13 -.21 -.07

28 -.58 -.77 -.90 -.82 -.81 — — -.41 -.41 -.36 -.18 -.05

29 -.61 -.78 -.90 -.82 — — — -.38 -.35 -.31 -.15 -.02

30 -.61 -.78 -.90 -.83 — — — -.37 -.27 -.26 -.12 -.01

31 -.61 — -.89 -.83 — — — -.35 — -.23 -.09 —
22 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 14. Daily mean water levels at pond F, 1995, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.00 -0.46 -0.65 -0.72 -0.97 0-.81 -0.98 -0.77 -0.23 -0.30 0.00 0.04

2 .01 -.46 -.65 -.72 -.97 -.83 -.98 -.77 -.30 -.28 .08 -.16

3 .04 -.46 -.65 -.73 -.96 -.87 -.98 -.77 -.37 -.26 .13 -.15

4 -.05 -.45 -.65 -.77 -.97 -.86 -.98 -.75 -.35 -.22 .23 -.13

5 -.28 -.46 -.65 -.77 -.97 -.86 -.97 -.72 -.32 -.17 .26 -.12

6 -.31 -.62 -.65 -.77 -.96 -.85 -.97 -.71 -.31 -.14 .27 -.19

7 -.34 -.63 -.65 -.77 -.96 -.84 -.97 -.70 -.28 -.12 .34 -.57

8 -.34 -.63 -.66 -.77 -.95 -.84 -.96 -.68 -.23 -.11 .13 -.73

9 -.35 -.64 -.69 -.81 -.95 -.87 -.88 -.69 -.18 -.10 -.05 -.62

10 -.36 -.64 -.69 -.98 -.95 -.92 -.82 -.68 -.16 -.09 -.06 -.57

11 -.36 -.65 -.69 -.96 -.96 -.93 -.80 -.66 -.14 -.08 -.05 -.49

12 -.36 -.65 -.69 -.93 -.96 -.92 -.77 -.65 -.12 -.07 -.06 -.34

13 -.36 -.65 -.69 -.93 -.94 -.92 -.76 -.66 -.10 -.07 -.05 -.30

14 -.34 -.65 -.70 -.94 -.92 -.92 -.74 -.66 -.09 -.09 -.04 -.28

15 -.31 -.65 -.71 -.95 -.91 -.93 -.74 -.67 -.10 -.12 -.04 -.25

16 -.28 -.66 -.71 -.96 -.91 -.94 -.73 -.67 -.14 -.11 -.02 -.22

17 -.27 -.66 -.70 -.96 -.90 -.95 -.74 -.66 -.14 -.24 .00 -.19

18 -.27 -.66 -.70 -.96 -.90 -.95 -.75 -.64 -.13 -.47 .01 -.15

19 -.27 -.66 -.70 -.96 -.89 -.97 -.75 -.63 -.13 -.42 .02 -.13

20 -.26 -.66 -.72 -.96 -.89 -1.00 -.74 -.59 -.12 -.36 .11 -.10

21 -.26 -.66 -.78 -.96 -.88 -1.00 -.74 -.54 -.10 -.29 .14 -.16

22 -.26 -.66 -.78 -.97 -.85 -1.04 -.73 -.50 -.07 -.25 .17 -.48

23 -.26 -.66 -.77 -.98 -.84 -1.04 -.72 -.46 -.06 -.23 .21 -.80

24 -.26 -.66 -.77 -.97 -.84 -1.03 -.72 -.44 -.05 -.21 .30 -.76

25 -.26 -.66 -.75 -.97 -.84 -1.02 -.68 -.42 -.03 -.19 .32 -.73

26 -.35 -.66 -.73 -.97 -.83 -1.01 -.73 -.40 -.01 -.18 .33 -.75

27 -.47 -.66 -.73 -.98 -.83 -.99 -.79 -.38 .01 -.16 .35 -.81

28 -.47 -.65 -.72 -.99 -.82 -.99 -.78 -.35 -.15 -.14 .44 -.78

29 -.47 -.65 -.72 -.97 — -.99 -.78 -.33 -.37 -.11 .47 -.75

30 -.46 -.65 -.72 -.97 — -.99 -.77 -.30 -.33 -.09 .43 -.71

31 -.46 — -.72 -.97 — -.98 — -.28 — -.06 .21 —
Tables 23

Table 15. Daily mean water levels at the extensometer, 1993, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 — — — — — -0.42 -0.43 -0.20 -0.23 -0.23 -0.18 -0.25

2 — — — — — -.40 -.43 -.19 -.23 -.23 -.18 -.24

3 — — — — — -.39 -.43 -.21 -.24 -.23 -.18 -.23

4 — — — — — -.37 -.42 -.22 -.26 -.23 -.19 -.24

5 — — — — — -.36 -.41 -.21 -.28 -.24 -.19 -.24

6 — — — — — -.35 -.40 -.22 -.29 -.24 -.19 -.24

7 — — — — — -.34 -.39 -.21 -.31 -.24 -.19 -.24

8 — — — — — -.34 -.38 -.20 -.30 -.24 -.18 -.24

9 — — — — — -.34 -.38 -.19 -.28 -.23 -.17 -.24

10 — — — — — -.34 -.37 -.19 -.29 -.22 -.16 -.25

11 — — — — — -.34 -.35 -.19 -.34 -.22 -.17 -.24

12 — — — — -0.38 -.34 -.33 -.19 -.33 -.21 -.18 -.24

13 — — — — -.45 -.33 -.32 -.19 -.31 -.21 -.21 -.24

14 — — — — -.43 -.34 -.31 -.18 -.37 -.20 -.23 -.24

15 — — — — -.42 -.33 -.30 -.16 -.40 -.20 -.24 -.26

16 — — — — -.42 -.33 -.28 -.16 -.40 -.19 -.24 -.26

17 — — — — -.42 -.35 -.31 -.15 -.38 -.18 -.22 -.27

18 — — — — -.44 -.35 -.30 -.15 -.38 -.16 -.21 -.27

19 — — — — -.47 -.36 -.30 -.16 -.37 -.17 -.21 -.28

20 — — — — -.48 -.35 -.29 -.18 -.37 -.17 -.20 -.29

21 — — — — -.49 -.35 -.29 -.19 -.37 -.16 -.19 -.30

22 — — — — -.49 -.35 -.29 -.19 -.35 -.15 -.18 -.30

23 — — — — -.49 -.37 -.29 -.19 -.33 -.15 -.17 -.31

24 — — — — -.47 -.39 -.30 -.22 -.29 -.16 -.17 -.30

25 — — — — -.46 -.39 -.30 -.24 -.26 -.18 -.18 -.29

26 — — — — -.47 -.41 -.30 -.25 -.25 -.21 -.19 -.28

27 — — — — -.45 -.42 -.28 -.25 -.24 -.22 -.20 -.27

28 — — — — -.44 -.43 -.27 -.24 -.24 -.24 -.21 -.28

29 — — — — — -.43 -.24 -.23 -.23 -.24 -.21 -.28

30 — — — — — -.43 -.22 -.22 -.22 -.22 -.23 -.29

31 — — — — — -.42 — -.23 — -.19 -.24 —
24 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 16. Daily mean water levels at the extensometer, 1994, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface, in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 -0.29 -0.45 -0.49 -0.48 -0.42 -0.34 -0.24 -0.20 -0.15 -0.01 -0.02 0.01

2 -.30 -.45 -.47 -.47 -.41 -.33 -.23 -.19 -.14 .00 -.02 .00

3 -.30 -.45 -.46 -.46 -.40 -.32 -.23 -.17 -.12 .00 -.01 .00

4 -.31 -.46 -.46 -.46 -.40 -.31 -.22 -.16 -.12 -.02 -.01 .00

5 -.32 -.46 -.44 -.45 -.39 -.31 -.21 -.16 -.12 -.05 -.01 .01

6 -.33 -.46 -.44 -.44 -.40 -.31 -.21 -.18 -.12 -.06 -.01 .00

7 -.34 -.46 -.44 -.44 -.45 -.30 -.20 -.21 -.12 -.06 -.01 -.01

8 -.34 -.46 -.44 -.46 -.44 -.30 -.20 -.21 -.11 -.08 -.01 -.01

9 -.34 -.47 -.46 -.48 -.43 -.30 -.22 -.21 -.11 -.09 -.01 -.01

10 -.35 -.48 -.47 -.49 -.43 -.30 -.22 -.22 -.11 -.09 .00 -.01

11 -.36 -.50 -.51 -.49 -.42 -.29 -.21 -.22 -.12 -.09 .01 -.01

12 -.36 -.50 -.52 -.48 -.40 -.27 -.21 -.21 -.13 -.09 .03 -.02

13 -.36 -.49 -.51 -.48 -.39 -.25 -.21 -.20 -.13 -.08 .06 -.03

14 -.37 -.47 -.54 -.49 -.39 -.25 -.21 -.20 -.12 -.07 .06 -.03

15 -.38 -.46 -.54 -.50 -.38 -.25 -.21 -.19 -.10 -.06 .07 -.02

16 -.40 -.46 -.52 -.50 -.39 -.25 -.20 -.19 -.09 -.06 .07 -.03

17 -.41 -.46 -.51 -.49 -.43 -.24 -.19 -.20 -.08 -.05 .06 -.04

18 -.42 -.46 -.50 -.47 -.43 -.25 -.19 -.21 -.07 -.06 .02 -.05

19 -.43 -.44 -.49 -.48 -.42 -.25 -.18 -.21 -.06 -.08 .02 -.06

20 -.42 -.44 -.47 -.49 -.43 -.24 -.17 -.20 -.07 -.08 .03 -.07

21 -.41 -.44 -.46 -.48 -.41 -.23 -.16 -.19 -.08 -.08 .02 -.08

22 -.42 -.45 -.44 -.48 -.39 -.23 -.15 -.19 -.08 -.09 .02 -.09

23 -.41 -.45 -.44 -.50 -.37 -.23 -.16 -.18 -.08 -.10 .02 -.11

24 -.41 -.44 -.42 -.51 -.37 -.24 -.17 -.19 -.08 -.08 .02 -.12

25 -.40 -.44 -.43 -.50 -.36 -.25 -.18 -.19 -.07 -.07 .02 -.14

26 -.40 -.44 -.44 -.49 -.37 -.25 -.20 -.21 -.06 -.05 .02 -.15

27 -.41 -.45 -.45 -.48 -.36 -.25 -.20 -.21 -.05 -.04 .03 -.17

28 -.42 -.47 -.45 -.47 -.35 -.26 -.21 -.21 -.04 -.03 .03 -.17

29 -.43 -.50 -.45 -.45 — -.26 -.21 -.18 -.02 -.02 .03 -.17

30 -.43 -.51 -.47 -.45 — -.25 -.21 -.17 -.02 -.01 .03 -.17

31 -.44 — -.48 -.44 — -.24 — -.17 — -.01 .02 —
Tables 25

Table 17. Daily mean water levels at the extensometer, 1995, Twitchell Island, California

[Missing data are denoted by —. Water levels are relative to land surface: Positive values signify measurements that are below land surface; negative values 

signify measurements that are above land surface]

Day

Depth of water level below land surface , in feet

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 -0.18 -0.30 -0.31 -0.33 -0.43 -0.27 -0.42 -0.31 -0.17 -0.17 -0.03 -0.14

2 -.19 -.32 -.32 -.34 -.41 -.30 -.39 -.31 -.17 -.17 -.03 -.15

3 -.20 -.32 -.34 -.37 -.38 -.32 -.38 -.31 -.16 -.15 -.03 -.15

4 -.23 -.32 -.35 -.39 -.37 -.31 -.36 -.30 -.14 -.14 -.03 -.15

5 -.25 -.35 -.35 -.40 -.36 -.32 -.36 -.30 -.13 -.12 -.05 -.15

6 -.27 -.36 -.36 -.40 -.35 -.32 -.36 -.28 -.10 -.10 -.08 -.15

7 -.27 -.36 -.36 -.41 -.35 -.33 -.36 -.27 -.07 -.08 -.10 -.15

8 -.26 -.35 -.34 -.44 -.35 -.34 -.36 -.26 -.06 -.07 -.10 -.16

9 -.25 -.36 -.33 -.49 -.35 -.39 -.34 -.25 -.05 -.08 -.12 -.17

10 -.26 -.36 -.32 -.56 -.36 -.45 -.32 -.25 -.05 -.09 -.15 -.17

11 -.25 -.36 -.31 -.51 -.38 -.47 -.31 -.25 -.06 -.09 -.17 -.17

12 -.25 -.36 -.33 -.52 -.39 -.47 -.31 -.26 -.07 -.10 -.18 -.17

13 -.26 -.35 -.33 -.53 -.41 -.49 -.31 -.28 -.08 -.09 -.17 -.18

14 -.27 -.34 -.34 -.54 -.41 -.51 -.30 -.30 -.10 -.09 -.17 -.17

15 -.26 -.35 -.34 -.53 -.39 -.52 -.30 -.31 -.14 -.09 -.17 -.17

16 -.25 -.36 -.33 -.52 -.37 -.53 -.32 -.31 -.17 -.08 -.18 -.17

17 -.24 -.36 -.33 -.49 -.35 -.52 -.33 -.32 -.17 -.10 -.18 -.16

18 -.24 -.35 -.32 -.45 -.34 -.52 -.34 -.30 -.18 -.09 -.16 -.15

19 -.26 -.34 -.31 -.43 -.32 -.50 -.34 -.29 -.18 -.09 -.15 -.15

20 -.27 -.34 -.30 -.43 -.32 -.50 -.34 -.28 -.16 -.11 -.13 -.15

21 -.27 -.34 -.28 -.42 -.32 -.51 -.33 -.27 -.15 -.12 -.13 -.16

22 -.28 -.34 -.28 -.43 -.32 -.56 -.30 -.26 -.14 -.11 -.13 -.17

23 -.29 -.33 -.28 -.45 -.31 -.56 -.29 -.24 -.14 -.10 -.13 -.18

24 -.29 -.33 -.28 -.47 -.31 -.54 -.28 -.23 -.13 -.09 -.13 -.18

25 -.30 -.34 -.27 -.46 -.30 -.52 -.28 -.22 -.13 -.09 -.15 -.18

26 -.30 -.33 -.26 -.46 -.29 -.48 -.27 -.22 -.13 -.09 -.16 -.19

27 -.30 -.32 -.26 -.49 -.28 -.47 -.27 -.21 -.15 -.09 -.14 -.19

28 -.30 -.31 -.28 -.48 -.27 -.46 -.28 -.20 -.16 -.07 -.13 -.19

29 -.29 -.31 -.30 -.48 — -.43 -.29 -.20 -.17 -.07 -.13 -.19

30 -.29 -.30 -.31 -.45 — -.42 -.30 -.19 -.17 -.06 -.12 -.15

31 -.28 — -.32 -.44 — -.42 — -.18 — -.04 -.13 — 
26 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 18. Mean spirit levels at pond S, Twitchell Island, California

[Missing data are denoted by —. See fig. 2 for location of leveling points. Levels are in feet below sea level]

Date

Leveling point

S1L S1H S2L S2H S3L S3H S4L S4H

11/15/92 -7.63 — -7.33 — -7.37 -4.52 -7.41 -4.51

12/3/92 -7.58 -4.73 -7.29 -4.40 -7.32 -4.48 -7.37 -4.47

1/27/93 -7.59 -4.73 -7.28 -4.39 -7.31 -4.46 -7.35 -4.45

2/22/93 -7.57 -4.71 -7.28 -4.39 -7.31 -4.46 -7.37 -4.46

3/24/93 -7.60 -4.73 -7.31 -4.42 -7.34 -4.49 -7.40 -4.49

4/12/93 -7.61 -4.74 -7.32 -4.43 -7.35 -4.49 -7.41 -4.50

4/29/93 -7.64 -4.77 -7.36 -4.47 -7.38 -4.53 -7.45 -4.54

5/6/93 -7.65 -4.78 -7.37 -4.48 -7.40 -4.58 -7.47 -4.56

6/7/93 -7.66 -4.79 -7.38 -4.49 -7.41 -4.55 -7.48 -4.56

6/29/93 -7.68 -4.80 -7.39 -4.50 -7.42 -4.56 -7.48 -4.57

7/13/93 -7.69 -4.82 -7.40 -4.51 -7.43 -4.57 -7.49 -4.58

7/26/93 -7.67 -4.80 -7.39 -4.50 -7.40 -4.56 -7.48 -4.57

8/12/93 -7.66 -4.79 -7.38 -4.49 -7.41 -4.54 -7.47 -4.56

8/23/93 -7.65 -4.78 -7.37 -4.48 -7.40 -4.54 -7.46 -4.55

9/8/93 -7.63 -4.76 -7.34 -4.45 -7.38 -4.52 -7.44 -4.53

9/21/93 -7.62 -4.75 -7.34 -4.45 -7.37 -4.51 -7.44 -4.52

10/20/93 -7.59 -4.72 -7.31 -4.42 -7.34 -4.48 -7.41 -4.49

11/19/93 -7.60 -4.74 -7.32 -4.43 -7.34 -4.49 -7.41 -4.49

12/1/93 -7.57 -4.70 -7.29 -4.40 -7.32 -4.47 -7.39 -4.48

1/5/94 -7.53 -4.66 -7.25 -4.36 -7.28 -4.43 -7.35 -4.44

1/21/94 -7.54 -4.67 -7.25 -4.36 -7.31 -4.43 -7.35 -4.44

2/4/94 -7.53 -4.66 -7.24 -4.36 -7.28 -4.42 -7.35 -4.44

2/16/94 -7.52 -4.65 -7.24 -4.35 -7.27 -4.42 -7.35 -4.44

3/2/94 -7.53 -4.66 -7.25 -4.36 -7.28 -4.43 -7.35 -4.44

3/14/94 -7.54 -4.67 -7.26 -4.37 -7.29 -4.44 -7.37 -4.45

3/28/94 -7.54 -4.67 -7.27 -4.38 -7.31 -4.45 -7.38 -4.47

4/13/94 -7.56 -4.69 -7.29 -4.40 -7.33 -4.47 -7.41 -4.49

5/2/94 -7.57 -4.70 -7.31 -4.42 -7.34 -4.48 -7.42 -4.50

5/26/94 -7.57 -4.70 -7.31 -4.42 -7.35 -4.49 -7.43 -4.51

6/8/94 -7.59 -4.72 -7.33 -4.44 -7.37 -4.51 -7.45 -4.53

7/1/94 -7.64 -4.76 -7.37 -4.47 -7.41 -4.54 -7.49 -4.57

7/13/94 -7.62 -4.75 -7.36 -4.46 -7.40 -4.53 -7.48 -4.56

7/29/94 -7.64 -4.76 -7.37 -4.48 -7.41 -4.54 -7.49 -4.57

8/23/94 -7.63 -4.76 -7.36 -4.47 -7.40 -4.54 -7.49 -4.57

9/9/94 -7.63 -4.76 -7.37 -4.48 -7.41 -4.55 -7.49 -4.57

11/1/94 -7.61 -4.74 -7.33 -4.44 — — -7.45 -4.53

12/5/94 -7.57 -4.70 -7.30 -4.41 -7.34 -4.49 -7.42 -4.51

1/23/95 -7.53 -4.66 -7.25 -4.37 -7.29 -4.44 -7.38 -4.46

2/22/95 -7.52 -4.65 -7.25 -4.37 -7.29 -4.44 -7.38 -4.46

4/12/95 -7.52 -4.65 -7.24 -4.36 -7.28 -4.43 -7.38 -4.46

5/16/95 -7.59 -4.72 -7.31 -4.43 -7.35 -4.50 -7.43 -4.52

6/27/95 -7.59 -4.71 -7.32 -4.43 -7.36 -4.50 -7.48 -4.54

7/25/95 -7.62 -4.74 -7.35 -4.47 -7.39 -4.54 -7.49 -4.57

8/30/95 -7.65 -4.69 -7.38 -4.43 -7.49 -4.60 -7.38 -4.47
Tables 27

Table 19. Mean spirit levels at pond M, Twitchell Island, California

[Missing data are denoted by —. See fig. 2 for location of leveling points. Levels are in feet below sea level]

Date Leveling point

M1L M1H M2L M2H M3L M3H M4L M4H

11/15/92 -7.49 -4.56 -7.61 -4.74 -7.49 -4.58 -7.48 -4.58

12/3/92 -7.45 -4.63 -7.57 -4.71 -7.47 -4.56 -7.45 -4.57

1/27/93 -7.48 -4.54 -7.62 -4.75 -7.52 -4.61 -7.50 -4.61

2/22/93 -7.47 -4.55 -7.61 -4.75 -7.51 -4.61 -7.50 -4.60

3/24/93 -7.48 -4.56 -7.62 -4.76 -7.53 -4.62 -7.52 -4.62

4/12/93 -7.50 -4.57 -7.64 -4.77 -7.54 -4.63 -7.54 -4.64

4/29/93 -7.55 -4.62 -7.68 -4.81 -7.59 -4.68 -7.59 -4.69

5/6/93 -7.57 -4.65 -7.71 -4.84 -7.62 -4.71 -7.62 -4.71

6/7/93 -7.57 -4.64 -7.70 -4.84 -7.61 -4.70 -7.61 -4.70

6/29/93 -7.59 -4.66 -7.73 -4.86 -7.64 -4.72 -7.63 -4.72

7/13/93 -7.60 -4.67 -7.74 -4.87 -7.64 -4.73 -7.63 -4.73

7/26/93 -7.59 -4.66 -7.72 -4.85 -7.62 -4.71 -7.62 -4.71

7/27/93 -7.58 -4.65 -7.72 -4.86 -7.63 -4.72 -7.62 -4.71

7/28/93 -7.57 -4.64 -7.71 -4.84 -7.62 -4.70 -7.61 -4.70

7/29/93 -7.56 -4.64 -7.70 -4.84 -7.61 -4.70 -7.60 -4.70

7/30/93 -7.57 -4.64 -7.71 -4.84 -7.61 -4.70 -7.61 -4.70

7/31/93 -7.57 -4.64 -7.70 -4.83 -7.61 -4.70 -7.60 -4.69

8/2/93 -7.57 -4.64 -7.70 -4.83 -7.61 -4.70 -7.60 -4.70

8/4/93 -7.57 -4.64 -7.71 -4.84 -7.61 -4.70 -7.61 -4.70

8/12/93 -7.57 -4.64 -7.71 -4.84 -7.62 -4.70 -7.61 -4.70

8/23/93 -7.56 -4.63 -7.70 -4.83 -7.60 -4.69 -7.60 -4.69

9/7/93 -7.53 -4.60 -7.67 -4.80 -7.57 -4.66 -7.57 -4.66

9/8/93 -7.55 -4.62 -7.70 -4.83 -7.60 -4.69 — -4.69

9/21/93 -7.53 -4.60 -7.67 -4.80 -7.57 -4.66 — -4.66

10/20/93 -7.49 -4.56 -7.62 -4.75 -7.52 -4.61 — -4.61

11/19/93 -7.51 -4.59 -7.66 -4.79 -7.56 -4.65 — -4.65

12/1/93 -7.50 -4.58 -7.65 -4.78 -7.55 -4.64 — -4.64

1/5/94 -7.47 -4.54 -7.60 -4.74 -7.51 -4.60 — -4.60

1/21/94 -7.45 -4.53 -7.59 -4.72 -7.49 -4.58 — -4.58

2/4/94 -7.46 -4.54 -7.60 -4.73 -7.50 -4.59 — -4.60

2/16/94 -7.47 -4.55 -7.61 -4.75 -7.52 -4.61 — -4.61

3/2/94 -7.48 -4.56 -7.63 -4.76 -7.53 -4.62 — -4.62

3/14/94 -7.48 -4.56 -7.63 -4.76 -7.53 -4.62 — -4.63

3/28/94 -7.50 -4.58 -7.64 -4.78 -7.55 -4.64 — -4.64

4/13/94 -7.52 -4.60 -7.66 -4.80 -7.57 -4.66 — -4.66

5/2/94 -7.51 -4.59 -7.65 -4.79 -7.56 -4.64 — -4.65

5/26/94 -7.53 -4.61 -7.66 -4.78 -7.56 -4.65 — -4.66

6/8/94 -7.55 -4.63 -7.69 -4.81 -7.59 -4.68 — -4.69

7/1/94 -7.60 -4.68 -7.76 -4.88 -7.66 -4.74 — -4.75

7/13/94 -7.60 -4.67 -7.75 -4.87 -7.65 -4.73 — -4.73

7/29/94 -7.60 -4.67 -7.75 -4.87 -7.65 -4.73 — -4.73

8/23/94 -7.60 -4.68 -7.75 -4.88 -7.66 -4.74 — -4.74

9/9/94 -7.61 -4.68 -7.75 -4.88 -7.66 -4.74 — -4.74

11/1/94 -7.57 -4.64 -7.72 -4.85 -7.62 -4.71 — -4.70

12/5/94 -7.55 -4.63 -7.70 -4.83 -7.60 -4.69 — -4.68

1/23/95 -7.54 -4.62 -7.69 -4.82 -7.60 -4.69 — -4.68

2/22/95 -7.55 -4.63 -7.70 -4.84 -7.61 -4.70 — -4.69

4/12/95 -7.53 -4.61 -7.69 -4.82 -7.59 -4.68 — -4.68

5/16/95 -7.56 -4.65 -7.72 -4.86 -7.63 -4.72 — -4.72

6/27/95 -7.56 -4.65 -7.72 -4.85 -7.63 -4.72 — -4.72

7/25/95 -7.60 -4.69 -7.76 -4.89 -7.67 -4.76 — -4.76

8/30/95 -7.63 -4.71 -7.79 -4.92 -7.70 -4.79 — —
28 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 20. Mean spirit levels at pond F, Twitchell Island, California

[See fig. 2 for location of leveling points. Levels are in feet below sea level]

Date

Leveling point

F1L F1H F2L F2H F3L F3H F4L F4H

11/15/92 -7.63 -4.60 -7.52 -4.63 -7.45 -4.54 -7.52 -4.61

12/3/92 -7.58 -4.64 -7.54 -4.67 -7.46 -4.57 -7.54 -4.64

1/27/93 -7.56 -4.64 -7.54 -4.67 -7.46 -4.57 -7.54 -4.64

2/22/93 -7.57 -4.65 -7.55 -4.68 -7.48 -4.57 -7.55 -4.64

3/24/93 -7.59 -4.67 -7.56 -4.69 -7.48 -4.59 -7.55 -4.65

4/12/93 -7.59 -4.67 -7.57 -4.69 -7.48 -4.59 -7.55 -4.66

4/29/93 -7.62 -4.70 -7.59 -4.72 -7.51 -4.61 -7.57 -4.68

5/6/93 -7.67 -4.75 -7.65 -4.77 -7.55 -4.66 -7.62 -4.72

6/7/93 -7.59 -4.67 -7.56 -4.69 -7.48 -4.59 -7.56 -4.66

6/29/93 -7.61 -4.69 -7.59 -4.71 -7.52 -4.61 -7.57 -4.67

7/13/93 -7.65 -4.72 -7.63 -4.75 -7.55 -4.65 -7.60 -4.70

7/26/93 -7.66 -4.73 -7.64 -4.76 -7.56 -4.66 -7.61 -4.71

8/12/93 -7.62 -4.69 -7.60 -4.72 -7.54 -4.62 -7.58 -4.68

8/23/93 -7.61 -4.67 -7.58 -4.70 -7.53 -4.60 -7.56 -4.67

9/8/93 -7.62 -4.68 -7.60 -4.71 -7.52 -4.61 -7.58 -4.67

9/21/93 -7.60 -4.65 -7.57 -4.68 -7.51 -4.58 -7.55 -4.65

10/20/93 -7.56 -4.62 -7.54 -4.65 -7.47 -4.56 -7.53 -4.63

11/19/93 -7.55 -4.61 -7.53 -4.64 -7.45 -4.54 -7.51 -4.61

12/1/93 -7.56 -4.62 -7.54 -4.65 -7.46 -4.56 -7.53 -4.62

1/5/94 -7.57 -4.63 -7.55 -4.66 -7.47 -4.57 -7.54 -4.63

1/21/94 -7.56 -4.62 -7.55 -4.66 -7.47 -4.56 -7.53 -4.63

2/4/94 -7.57 -4.63 -7.56 -4.67 -7.48 -4.57 -7.54 -4.64

2/16/94 -7.58 -4.64 -7.57 -4.68 -7.49 -4.59 -7.55 -4.65

3/2/94 -7.60 -4.65 -7.59 -4.70 -7.51 -4.60 -7.57 -4.66

3/14/94 -7.61 -4.67 -7.59 -4.70 -7.52 -4.61 -7.57 -4.67

3/28/94 -7.60 -4.66 -7.59 -4.69 -7.50 -4.60 -7.57 -4.66

4/13/94 -7.60 -4.66 -7.59 -4.69 -7.51 -4.60 -7.57 -4.66

5/2/94 -7.60 -4.66 -7.58 -4.69 -7.50 -4.59 -7.56 -4.65

5/26/94 -7.63 -4.69 -7.62 -4.73 -7.54 -4.63 -7.59 -4.69

6/8/94 -7.65 -4.71 -7.64 -4.75 -7.56 -4.65 -7.61 -4.70

7/1/94 -7.68 -4.74 -7.66 -4.77 -7.58 -4.67 -7.62 -4.72

7/13/94 -7.65 -4.71 -7.63 -4.74 -7.55 -4.64 -7.61 -4.70

7/29/94 -7.67 -4.72 -7.65 -4.76 -7.57 -4.66 -7.63 -4.72

8/23/94 -7.68 -4.73 -7.66 -4.77 -7.58 -4.68 -7.64 -4.73

9/9/94 -7.69 -4.75 -7.68 -4.79 -7.60 -4.69 -7.64 -4.74

11/1/94 -7.61 -4.66 -7.57 -4.70 -7.52 -4.61 -7.58 -4.67

12/5/94 -7.59 -4.64 -7.55 -4.69 -7.50 -4.60 -7.56 -4.66

1/23/95 -7.60 -4.65 -7.56 -4.69 -7.50 -4.60 -7.55 -4.65

2/22/95 -7.64 -4.69 -7.61 -4.74 -7.55 -4.65 -7.60 -4.70

4/12/95 -7.64 -4.69 -7.61 -4.74 -7.55 -4.64 -7.60 -4.69

5/16/95 -7.66 -4.70 -7.62 -4.75 -7.56 -4.65 -7.61 -4.71

6/27/95 -7.68 -4.73 -7.64 -4.77 -7.58 -4.67 -7.64 -4.73

7/25/95 -7.70 -4.77 -7.66 -4.79 -7.60 -4.69 -7.66 -4.74

8/30/95 -7.70 -4.77 -7.66 -4.79 -7.60 -4.69 -7.67 -4.75
Tables 29

Table 21. Mean spirit levels at the control sites and extensometer, Twitchell Island, California

[Missing data are denoted by —. See fig. 2 for location of control sites and extensometer. Levels are in feet below sea level]

Date

Control site Extensometer

SM MF Plate Table

11/15/92 — — — —

12/03/92 — — — —

01/27/93 — — — —

02/22/93 — — -7.14 -6.91

03/24/93 — — -7.15 -6.90

04/12/93 — — -7.15 -6.90

04/29/93 — — -7.16 -6.90

05/06/93 -7.53 -7.59 -7.17 -6.90

06/07/93 -7.54 -7.60 -7.17 -6.90

06/29/93 -7.55 -7.62 -7.17 -6.91

07/13/93 -7.56 -7.62 -7.18 -6.91

07/26/93 -7.54 -7.62 -7.20 -6.91

07/27/93 -7.54 -7.61 -7.20 -6.91

07/28/93 -7.54 -7.61 -7.20 -6.91

07/29/93 -7.52 -7.60 -7.20 -6.92

07/30/93 -7.53 -7.60 -7.20 -6.92

07/31/93 -7.54 -7.59 — —

08/02/93 -7.54 -7.59 -7.20 -6.92

08/04/93 -7.55 -7.60 -7.20 -6.92

08/12/93 -7.55 -7.60 -7.20 -6.92

08/23/93 -7.54 -7.59 -7.20 -6.92

09/07/93 -7.51 -7.56 -7.20 -6.92

09/08/93 -7.51 -7.57 -7.20 -6.93

09/21/93 -7.51 -7.55 -7.18 -6.92

10/20/93 -7.46 -7.49 -7.14 -6.92

11/19/93 -7.43 -7.45 -7.12 -6.92

12/01/93 -7.44 -7.45 -7.12 -6.92

01/05/94 -7.43 -7.43 -7.11 -6.92

01/21/94 -7.42 -7.42 -7.11 -6.92

02/04/94 -7.42 -7.41 -7.11 -6.92

02/16/94 -7.43 -7.42 -7.11 -6.92

03/02/94 -7.44 -7.43 -7.11 -6.92

03/14/94 -7.46 -7.45 -7.13 -6.92

03/28/94 -7.52 -7.46 -7.13 -6.92

04/13/94 -7.56 -7.48 -7.14 -6.92

05/02/94 -7.58 -7.51 -7.14 -6.92

05/26/94 -7.60 -7.53 -7.14 -6.92

06/08/94 -7.62 -7.56 -7.14 -6.91

07/01/94 -7.67 -7.63 -7.16 -6.92

07/13/94 -7.66 -7.63 -7.17 -6.92

07/29/94 -7.67 -7.62 -7.19 -6.92

08/23/94 -7.66 -7.63 -7.21 -6.93

09/09/94 -7.65 -7.62 -7.21 -6.93

11/01/94 -7.59 -7.52 -7.15 -6.92

12/05/94 -7.58 -7.50 -7.13 -6.92

01/23/95 -7.53 -7.45 -7.11 -6.92

02/22/95 -7.55 -7.47 -7.12 -6.93

04/12/95 -7.54 -7.46 -7.12 -6.92

05/16/95 -7.58 -7.49 -7.13 -6.93

06/27/95 -7.61 -7.59 -7.15 -6.93

07/25/95 -7.66 -7.62 -7.17 -6.92

08/30/95 -7.67 -7.63 -7.18 -6.93
30 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 22. Daily mean elevation change relative to established datum as measured by extensometer, 1993, Twitchell Island, California

[Missing data are denoted by —. Values are in feet]

Day Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 — — — — 0.04 0.03 0.03 0.00 -0.01 0.00 -0.01 -0.01

2 — — — — .03 .02 .03 .00 -.01 .00 -.01 -.01

3 — — — — .03 .02 .03 .00 .00 .00 -.02 -.01

4 — — — — .03 .02 .03 .00 .00 .00 -.02 -.01

5 — — — — .03 .02 .03 .00 .00 .00 -.02 -.01

6 — — — — .03 .02 .03 .00 .00 .00 -.02 -.01

7 — — — — .03 .01 .03 .00 .00 .00 -.02 -.01

8 — — — — .03 .01 .03 .00 .00 .00 -.02 -.01

9 — — — — .03 .01 .03 .00 .00 .00 -.02 -.01

10 — — — — .03 .01 .02 -.01 .00 .00 -.02 -.01

11 — — — — .03 .01 .02 -.01 .01 .00 -.02 -.01

12 — — — — .03 .01 .02 -.01 .02 .00 -.02 -.01

13 — — — — .03 .01 .02 -.01 .01 -.01 -.01 -.01

14 — — — — .03 .01 .02 -.01 .02 -.01 -.01 -.01

15 — — — — .03 .01 .01 -.01 .03 -.01 -.01 .00

16 — — — — .02 .01 .01 -.01 .02 -.01 -.01 .00

17 — — — — .02 .02 .01 -.01 .02 -.01 -.01 .00

18 — — — — .02 .02 .01 -.01 .02 -.01 -.01 .00

19 — — — — .03 .02 .01 -.01 .02 -.01 -.01 .00

20 — — — — .03 .02 .01 -.01 .02 -.01 -.01 .00

21 — — — — .03 .02 .01 -.01 .02 -.01 -.01 .01

22 — — — — .03 .02 .01 -.01 .02 -.01 -.01 .01

23 — — — — .03 .02 .01 -.01 .01 -.02 -.01 .01

24 — — — — .03 .02 .01 -.01 .01 -.02 -.02 .01

25 — — — — .03 .02 .01 -.01 .01 -.02 -.02 .01

26 — — — — .03 .03 .01 -.01 .01 -.01 -.02 .01

27 — — — — .03 .03 .01 .00 .00 -.01 -.01 .01

28 — — — -0.05 .03 .03 .01 .00 .00 -.01 -.01 .01

29 — — — -.01 — .03 .00 -.01 .00 -.01 -.01 .01

30 — — — .04 — .03 .00 -.01 .00 -.01 -.01 .01

31 — — — .04 — .03 — -.01 — -.01 -.01 —
Tables 31

Table 23. Daily mean elevation change relative to established datum as measured by extensometer, 1994, Twitchell Island, California

[Missing data are denoted by —. Values are in feet]

Day Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.01 0.05 0.06 0.06 0.07 0.06 0.05 0.04 0.04 0.02 0.00 -0.02

2 .01 .05 .06 .06 .06 .06 .05 .04 .04 .02 .00 -.02

3 .01 .05 .06 .06 .06 .06 .05 .04 .03 .01 .00 -.02

4 .01 .05 .06 .06 .06 .06 .04 .04 .03 .01 .00 -.01

5 .02 .05 .06 .06 .06 .06 .04 .04 .03 .01 .00 -.02

6 .02 .05 .06 .06 .06 .06 .04 .04 .03 .01 .00 -.02

7 .02 .05 .06 .06 .06 .06 .04 .04 .03 .01 .00 -.02

8 .02 .06 .06 .06 .07 .05 .04 .04 .03 .01 .00 -.02

9 .02 .05 .06 .06 .07 .05 .04 .04 .03 .01 .00 -.02

10 .02 .06 .06 .06 .07 .05 .04 .04 .03 .01 -.01 -.02

11 .02 .06 .06 .06 .07 .05 .04 .04 .03 .01 -.01 -.02

12 .03 .06 .06 .06 .06 .05 .04 .04 .03 .01 -.01 -.01

13 .03 .06 .06 .06 .06 .05 .04 .04 .03 .01 -.01 -.01

14 .03 .06 .06 .06 .06 .05 .04 .04 .03 .01 -.01 -.01

15 .03 .06 .07 .06 .06 .05 .04 .04 .03 .01 -.02 -.01

16 .03 .06 .07 .06 .06 .05 .04 .04 .03 .01 -.02 -.01

17 .04 .06 .07 .06 .06 .05 .04 .04 .03 .01 -.02 -.01

18 .04 .06 .07 .06 .06 .05 .04 .04 .03 .01 -.02 -.01

19 .04 .06 .07 .06 .06 .05 .04 .04 .02 .01 -.02 -.01

20 .04 .06 .06 .06 .06 .05 .04 .04 .02 .01 -.02 -.01

21 .04 .06 .06 .06 .06 .05 .04 .04 .02 .01 -.02 -.01

22 .04 .06 .06 .06 .06 .05 .04 .04 .03 .01 -.02 -.01

23 .04 .06 .06 .07 .06 .05 .04 .04 .03 .01 -.02 .00

24 .04 .06 .06 .07 .06 .05 .04 .04 .03 .01 -.02 .00

25 .04 .06 .06 .07 .06 .05 .04 .04 .02 .01 -.02 .00

26 .04 .06 .06 .07 .06 .05 .04 .04 .02 .01 -.02 .00

27 .04 .06 .06 .07 .06 .05 .04 .04 .02 .01 -.02 .01

28 .04 .06 .06 .07 .06 .05 .04 .04 .02 .01 -.02 .01

29 .04 .06 .06 .07 — .05 .04 .04 .02 .00 -.02 .01

30 .05 .06 .06 .07 — .05 .04 .04 .02 .00 -.02 .01

31 .05 — .06 .07 — .05 — .04 — .00 -.02 —
32 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 24. Daily mean elevation change relative to established datum as measured by extensometer, 1995, Twitchell Island, California

[Missing data are denoted by —. Values are in feet]

Day Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1 0.01 0.03 0.04 0.05 0.06 0.05 0.07 0.06 0.05 0.03 0.01 0.01

2 .01 .03 .04 .05 .06 .05 .07 .06 .04 .03 .00 .01

3 .01 .04 .04 .05 .06 .05 .07 .06 .04 .03 .00 .01

4 .02 .04 .05 .05 .06 .05 .07 .06 .04 .03 .00 .01

5 .02 .04 .05 .05 .06 .05 .07 .06 .04 .03 .00 .01

6 .02 .04 .05 .05 .06 .05 .07 .06 .04 .03 .00 .01

7 .02 .04 .05 .05 .06 .05 .07 .06 .03 .03 .00 .01

8 .02 .04 .05 .06 .06 .06 .07 .06 .03 .02 .00 .01

9 .02 .04 .05 .06 .06 .06 .07 .05 .03 .02 .00 .01

10 .02 .04 .04 .06 .06 .06 .07 .05 .03 .02 .01 .01

11 .02 .04 .04 .06 .06 .07 .07 .05 .03 .02 .01 .01

12 .02 .04 .04 .06 .06 .07 .07 .05 .03 .02 .02 .01

13 .02 .04 .05 .06 .06 .07 .06 .05 .03 .02 .02 .01

14 .02 .04 .05 .06 .06 .07 .06 .05 .02 .02 .02 .01

15 .02 .04 .05 .06 .06 .07 .06 .05 .03 .02 .02 .01

16 .02 .04 .05 .06 .06 .07 .06 .06 .03 .02 .02 .01

17 .02 .04 .05 .06 .06 .07 .06 .06 .03 .02 .02 .01

18 .02 .04 .05 .06 .06 .07 .06 .06 .03 .02 .02 .01

19 .02 .04 .05 .06 .06 .07 .06 .06 .03 .02 .02 .01

20 .02 .04 .04 .06 .06 .07 .06 .06 .03 .02 .02 .01

21 .03 .04 .04 .06 .06 .07 .06 .06 .03 .01 .02 .01

22 .03 .04 .04 .06 .06 .07 .06 .06 .03 .01 .02 .01

23 .03 .04 .04 .06 .06 .07 .06 .05 .03 .01 .02 .01

24 .03 .04 .04 .06 .06 .07 .06 .05 .03 .01 .01 .01

25 .03 .04 .04 .06 .05 .07 .06 .05 .03 .01 .02 .02

26 .03 .04 .04 .06 .05 .07 .06 .05 .03 .01 .02 .02

27 .03 .04 .04 .06 .05 .07 .06 .05 .03 .01 .02 .02

28 .03 .04 .04 .06 .05 .07 .06 .05 .03 .01 .02 .02

29 .03 .04 .04 .06 — .07 .06 .05 .03 .01 .02 .02

30 .03 .04 .04 .06 — .07 .06 .05 .03 .01 .01 .02

31 .03 — .04 .06 — .07 — .05 — .01 .01 —
Tables 33

Table 25. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

S1, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 31.58 22.8 0.000 46.489 7.358 0.986 — —

07/28/93 25.48 21.3 0.000 27.739 8.190 0.989 — —

08/12/93 28.66 21.6 0.000 27.978 3.017 0.856 — —

08/23/93 27.54 21.7 0.000 28.351 6.900 0.663 — —

09/08/93 34.60 20.9 0.000 28.138 2.763 0.998 — —

09/27/93 28.18 18.2 0.000 27.420 0.738 0.728 — —

10/06/93 21.30 17.1 0.000 27.978 2.395 0.953 — —

10/19/93 22.98 17.8 0.000 48.324 2.554 0.979 0.007 0.214

10/21/93 23.64 16.6 9.842 41.382 0.299 0.090 0.000 -0.331

10/22/93 20.90 — 17.264 36.648 0.276 0.861 0.005 -0.383

10/25/93 23.96 — 0.000 48.457 2.800 0.990 -0.001 -0.327

10/27/93 23.04 — 12.383 40.319 -0.260 0.127 0.004 0.072

10/29/93 22.98 — 0.000 48.085 2.835 0.930 -0.034 0.362

11/01/93 25.94 — 0.000 27.659 3.269 0.740 0.001 -0.284

11/05/93 23.74 — 0.000 48.139 2.410 0.953 0.007 0.969

11/18/93 16.64 9.1 0.000 48.350 0.785 0.986 0.003 0.315

11/30/93 14.70 9.0 0.000 48.936 0.866 0.419 -0.004 -0.100

01/10/94 9.96 — 14.605 38.404 0.300 0.835 -0.001 -0.113

01/20/94 14.46 — 10.160 41.489 — — -0.001 -0.173

02/02/94 11.78 — 7.779 22.872 — — 0.000 -0.059

02/04/94 13.00 — 5.398 27.255 0.010 -0.332 — —

02/16/94 18.74 — 0.000 27.659 — — 0.002 0.953

02/23/94 14.23 8.2 1.270 27.021 0.242 0.991 — —

03/02/94 20.82 — 0.000 27.766 — — 0.005 0.931

03/04/94 18.84 11.8 0.000 28.085 -0.079 0.234 — —

03/14/94 22.72 — 0.000 27.978 — — 0.002 0.988

03/16/94 17.12 11.1 0.000 27.659 2.054 0.978 — —

03/28/94 25.38 — 0.000 27.978 — — 0.003 0.973

04/11/94 19.18 11.9 0.000 27.553 -0.408 0.411 — —

04/13/94 27.98 — 0.000 27.819 — — 0.001 0.520

04/29/94 19.32 13.9 0.000 27.553 1.856 0.946 — —

05/02/94 25.06 — 0.000 30.531 — — 0.002 0.881

05/11/94 25.70 15.7 0.000 28.005 5.300 0.998 — —

05/18/94 26.90 — 0.000 27.659 — — 0.000 -0.138

05/20/94 24.44 15.6 0.000 27.446 4.548 0.987 — —

06/06/94 25.84 18.6 0.000 27.500 6.909 0.995 — —

06/08/94 29.80 — 0.000 27.712 — — -0.005 0.292

06/27/94 34.56 21.7 0.000 27.819 3.894 0.974 -0.004 0.036

07/14/94 31.00 23.6 0.000 27.978 7.421 0.998 0.001 -0.151

07/27/94 33.90 19.6 0.000 27.181 5.126 0.988 — —

07/29/94 36.64 — 0.000 27.340 — — -0.003 0.406

08/22/94 24.94 19.5 0.000 27.374 2.681 0.987 — —

09/08/94 26.44 19.6 0.000 27.234 2.761 0.994 — —

10/24/94 22.84 — 0.000 27.288 — — 0.000 0.340

10/26/94 23.62 14.3 0.000 27.234 2.918 0.987 — —

10/28/94 19.82 — 0.000 28.085 2.760 0.999 -0.001 0.154

11/01/94 19.78 — 6.350 22.978 2.732 0.986 -0.001 -0.241

11/23/94 12.12 6.8 6.191 23.191 0.987 0.902 — —

11/28/94 11.60 — 11.910 19.574 — — 0.000 -0.482

03/27/95 17.46 — 11.748 20.851 -0.068 -0.311 0.003 0.563

05/17/95 23.60 — 12.065 12.659 0.527 0.991 0.003 0.980

07/11/95 25.36 — 0.000 20.851 5.883 0.987 0.040 0.764

07/11/95 25.36 — 0.000 20.851 5.883 0.987 0.040 0.764
34 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 26. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

S2, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 31.12 22.80 0.00 45.851 1.264 0.958 -0.003 -0.100

07/28/93 25.70 21.70 0.00 27.659 2.061 0.999 — —

08/12/93 30.00 21.50 0.00 27.074 1.912 0.957 — —

08/23/93 33.32 22.60 0.00 27.207 1.942 0.918 — —

09/08/93 35.74 21.50 0.00 27.393 1.670 0.924 — —

09/27/93 28.76 19.90 0.00 26.835 2.907 0.540 — —

10/06/93 20.92 17.40 0.00 26.861 2.026 0.968 — —

10/19/93 25.08 17.40 0.00 47.686 1.346 0.936 -0.001 -0.256

10/21/93 23.32 16.90 2.30 46.276 0.511 0.341 -0.001 0.544

10/22/93 21.48 — 9.80 40.558 0.274 0.332 -0.004 0.202

10/25/93 25.14 — 0.00 47.606 2.837 0.908 0.013 0.256

10/27/93 25.16 — 4.29 44.574 0.143 0.467 -0.004 0.103

10/29/93 23.62 — 0.00 47.340 4.239 0.997 -0.014 -0.123

11/05/93 24.50 — 0.00 47.394 5.546 0.983 -0.001 -0.170

11/18/93 16.20 9.20 0.00 47.819 1.075 0.916 -0.003 -0.132

11/30/93 14.94 8.80 0.00 47.553 0.826 0.940 0.001 -0.315

01/10/94 10.63 6.00 6.67 42.340 0.706 0.446 0.001 -0.308

01/20/94 14.66 — 1.67 44.946 0.000 — 0.002 -0.386

02/02/94 12.12 — 0.00 27.340 0.000 — -0.001 0.775

02/04/94 14.78 — 0.00 27.340 0.015 -0.315 — —

02/16/94 17.84 — 0.00 26.702 0.000 — -0.001 0.395

02/23/94 15.20 7.90 0.00 26.595 0.451 0.999 — —

03/02/94 20.64 — 0.00 27.021 0.000 0.000 -0.319

03/04/94 19.62 12.40 0.00 27.606 0.269 0.202 — —

03/14/94 24.73 — 0.00 26.915 0.000 — 0.000 0.748

03/16/94 16.46 11.30 0.00 26.595 0.453 0.402 — —

03/28/94 24.36 — 0.00 26.808 0.000 — 0.000 0.469

04/11/94 21.20 13.70 0.00 26.702 0.555 0.973 — —

04/13/94 25.06 — 0.00 26.595 0.000 — 0.000 0.366

04/29/94 20.04 14.40 0.00 26.569 1.130 0.933

05/02/94 25.48 — 0.00 27.287 — — 0.004 0.755

05/11/94 25.96 16.90 0.00 26.782 3.337 0.975 — —

05/18/94 27.22 0.00 26.810 — — 0.004 0.726

05/20/94 25.82 16.40 0.00 26.622 2.715 0.985 — —

06/06/94 26.82 20.10 0.00 26.649 2.996 0.973 — —

06/08/94 24.62 — 0.00 26.968 — — 0.003 -0.192

06/27/94 33.48 24.00 0.00 27.234 2.149 0.972 0.001 -0.202

07/14/94 36.50 23.90 0.00 26.808 4.948 0.993 -0.002 0.803

07/27/94 36.90 23.40 0.00 26.915 2.482 0.982 — —

07/29/94 36.56 — 0.00 27.074 — — -0.003 0.673

08/22/94 26.74 21.70 0.00 26.276 0.872 0.936 — —

09/08/94 27.22 20.60 0.00 26.489 3.033 0.942 — —

10/24/94 23.84 — 0.00 26.649 — — 0.000 -0.198

10/26/94 24.72 14.20 0.00 26.542 1.742 0.950 — —

10/28/94 22.64 — 0.00 27.606 4.033 0.987 0.000 -0.185

11/01/94 20.02 — 0.00 26.808 2.550 0.983 -0.003 -0.226

11/23/94 13.54 7.30 0.00 26.861 1.151 0.996 — —

11/28/94 11.46 — 5.40 22.978 — — -0.001 0.339

12/20/94 9.88 — 0.00 26.861 1.047 0.982 — —

02/24/95 14.60 — 7.62 21.489 0.042 -0.228 0.001 0.286

03/27/95 19.02 — 3.33 24.149 -0.118 -0.228 0.001 0.411

04/17/95 15.48 — 10.64 19.574 -0.894 0.952 -0.001 0.501

05/17/95 22.82 — 4.45 16.170 1.406 0.994 0.003 0.621

06/22/95 34.54 — 0.00 18.936 6.193 0.994 0.015 0.986

07/11/95 26.38 — 0.00 19.042 3.061 0.996 0.007 0.990

09/07/95 32.56 — 0.00 22.127 1.203 0.891 — —
Tables 35

Table 27. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

S3, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/28/93 24.90 21.20 0.00 28.218 0.321 0.993 — —

08/12/93 31.42 21.10 0.00 27.606 1.504 0.941 — —

08/23/93 33.32 22.80 0.00 28.324 2.227 0.947 — —

09/08/93 35.38 21.90 0.00 28.165 2.222 0.976 — —

09/27/93 30.70 19.20 0.00 27.978 0.403 0.774 — —

10/06/93 21.84 17.80 0.00 27.978 0.901 0.943 — —

10/19/93 25.34 17.00 0.00 48.936 1.940 0.890 -0.005 0.770

10/21/93 22.84 16.70 3.97 45.957 0.561 0.286 0.000 -0.055

10/22/93 22.00 — 11.19 40.425 0.052 -0.226 -0.007 0.060

10/25/93 25.58 — 0.00 49.042 5.952 0.988 0.002 -0.320

10/27/93 24.74 — 6.99 44.733 0.507 0.786 -0.002 0.255

10/29/93 24.76 — 0.00 48.563 4.403 0.996 0.018 -0.202

11/05/93 24.74 — 0.00 48.297 5.987 0.991 -0.001 -0.290

11/18/93 17.26 9.50 0.00 48.616 1.199 0.822 0.000 -0.078

11/30/93 15.32 8.20 0.00 48.510 1.644 0.966 0.001 -0.163

01/10/94 11.20 — 9.21 42.446 0.045 -0.263 -0.001 -0.196

01/20/94 14.14 — 4.13 45.531 — — -0.001 0.123

02/02/94 12.78 — 2.22 26.489 — — 0.001 0.407

02/04/94 15.48 — 0.00 28.085 -0.038 -0.039 — —

02/16/94 18.84 — 0.00 28.085 — 0.002 0.801

02/23/94 15.73 8.00 0.00 28.191 0.302 0.978 — —

03/02/94 21.60 — 0.00 27.872 — 0.000 -0.117

03/04/94 20.74 13.00 0.00 28.085 0.349 0.452 — —

03/14/94 22.78 — 0.00 27.978 — 0.001 0.930

03/16/94 16.56 11.50 0.00 27.234 1.403 0.981 — —

03/28/94 24.62 — 0.00 27.872 — — 0.000 -0.268

04/11/94 22.32 13.20 0.00 27.393 1.234 0.950 — —

04/13/94 25.08 — 0.00 27.766 — — -0.001 0.214

04/29/94 19.92 14.50 0.00 27.579 4.019 0.998 — —

05/02/94 21.46 — 0.00 27.765 — — -0.001 0.599

05/11/94 24.96 16.70 0.00 27.367 5.041 0.997 — —

05/18/94 23.28 — 0.00 27.579 — — 0.000 -0.187

05/20/94 29.86 16.30 0.00 27.473 5.433 0.998 — —

06/06/94 27.12 19.80 0.00 27.553 7.742 0.996 — —

06/08/94 32.18 — 0.00 27.340 — — 0.000 -0.271

06/27/94 35.10 21.20 0.00 27.446 7.450 0.999 0.000 -0.332

07/14/94 39.76 25.50 0.00 27.234 6.531 0.999 -0.003 0.628

07/27/94 36.48 23.60 0.00 27.393 6.900 1.000 — —

07/29/94 40.44 — 0.00 27.925 — — -0.001 -0.038

08/22/94 27.04 23.00 0.00 27.446 2.897 0.997 — —

09/08/94 27.64 21.10 0.00 27.074 5.979 0.995 — —

10/24/94 23.24 — 0.00 27.021 — -0.001 0.666

10/26/94 24.22 14.90 0.00 27.367 2.040 0.995 — —

10/28/94 22.98 — 0.00 28.085 5.307 0.982 0.001 0.482

11/23/94 14.38 7.50 0.95 26.808 1.564 0.990 — —

11/28/94 11.38 — 7.62 22.127 — — 0.000 0.697

12/20/94 9.22 — 0.00 27.127 1.377 0.999 — —

02/24/95 14.98 — 10.16 20.638 0.055 0.165 0.001 0.114

04/17/95 15.74 — 12.38 18.404 -0.473 0.875 0.000 -0.237

06/22/95 33.46 — 0.00 20.213 8.875 0.993 0.161 0.966

09/07/95 33.88 — 0.00 22.021 0.754 0.948 — —
36 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

]

Table 28. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control site 

SM—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 — — — — — — — —

07/26/93 — — — — — — — —

07/27/93 27.94 23.50 0.00 28.750 2.745 0.998 -0.002 -0.136

07/28/93 22.50 22.60 0.00 28.750 4.485 0.978 0.000 -0.327

07/29/93 23.20 — 0.00 28.514 3.217 0.960 — —

07/30/93 28.54 23.50 0.00 28.298 3.345 0.987 — —

07/31/93 37.52 23.60 0.00 28.431 2.606 0.958 — —

08/02/93 35.40 25.10 0.00 28.563 4.189 0.978 — —

08/04/93 26.42 24.40 0.00 28.351 4.282 0.978 — —

08/12/93 29.84 23.60 0.00 28.377 -0.560 0.713 — —

08/23/93 35.70 25.20 0.00 28.457 6.710 0.827 — —

09/07/93 32.84 24.10 0.00 28.537 3.480 0.999 — —

09/08/93 28.62 23.80 0.00 28.484 2.875 0.980 — —

09/10/93 27.44 23.40 0.00 30.691 3.200 0.931 — —

09/13/93 29.24 22.50 0.00 30.372 3.233 0.978 — —

09/15/93 21.72 21.60 0.00 30.638 1.322 0.845 — —

09/27/93 32.30 21.60 0.00 28.457 1.569 0.985 — —

10/06/93 24.76 19.20 0.00 28.298 1.692 0.953 — —

10/19/93 25.90 17.80 0.00 28.457 2.099 0.989 0.099 0.988

10/21/93 23.38 17.20 0.00 27.978 1.216 0.913 0.005 0.984

10/22/93 25.06 17.00 0.00 28.271 0.879 0.883 0.017 0.691

10/25/93 27.24 17.20 0.00 28.138 1.124 0.964 0.040 0.997

10/27/93 27.34 17.10 0.00 28.457 0.859 0.964 0.043 0.988

10/29/93 25.80 16.70 0.00 28.085 0.999 0.970 0.121 0.975

11/01/93 25.06 — 0.00 28.244 0.733 0.870 0.059 0.987

11/05/93 25.12 — 0.00 28.112 1.604 0.870 0.150 0.905

11/18/93 20.16 10.40 0.00 28.191 1.852 0.992 0.000 0.743

11/30/93 14.12 8.50 0.00 28.244 2.593 0.930 -0.001 -0.100

01/10/94 10.46 6.50 0.71 27.500 0.018 -0.332 0.001 0.771

01/20/94 25.78 — 1.27 27.234 — — 0.002 0.096

02/02/94 11.54 — 0.40 27.924 — — 0.114 0.715

02/04/94 18.94 7.80 0.32 27.234 0.339 0.831 — —

02/16/94 20.32 — 0.00 28.298 — — 0.027 0.994

02/23/94 16.30 8.30 1.03 27.181 -0.102 0.267 — —

03/02/94 25.60 — 0.00 27.872 — — 0.087 0.990

03/04/94 22.36 13.10 0.00 28.085 0.484 0.162 — —

03/14/94 31.38 — 0.00 27.978 — — 0.016 0.952

03/16/94 16.80 13.20 0.00 27.446 -0.009 -0.332 — —

03/28/94 29.46 — 0.00 27.659 — — 0.012 0.976

04/11/94 23.42 14.20 0.00 27.287 3.642 0.875 — —

04/13/94 30.08 — 0.00 27.766 — — -0.022 -0.124

04/29/94 25.48 16.20 0.00 27.686 15.150 0.996 — —

05/11/94 25.38 17.30 0.00 27.633 7.071 0.971 — —

05/20/94 31.30 16.80 0.00 27.553 9.966 0.978 — —

Table 28. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control site 

SM, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]
Tables 37

06/06/94 30.48 20.70 0.00 27.500 16.370 0.999 — —

06/09/94 19.74 — 0.00 27.553 — — -0.006 0.244

06/20/94 33.18 21.00 0.00 27.633 3.299 0.971 0.001 0.456

06/22/94 35.30 21.40 0.00 27.633 3.339 0.997 0.000 -0.332

06/23/94 37.98 20.50 0.00 27.659 4.092 0.999 0.000 -0.321

06/24/94 37.30 21.10 0.00 27.766 4.436 0.986 0.000 -0.265

06/27/94 38.88 23.00 0.00 27.340 3.837 0.964 0.000 -0.333

06/29/94 28.08 23.00 0.00 27.606 3.619 0.988 0.001 0.098

07/01/94 38.04 21.40 0.00 27.500 3.884 0.947 — —

07/14/94 38.02 23.90 0.00 28.191 4.991 0.988 -0.001 -0.228

07/27/94 35.76 24.40 0.00 27.633 3.742 0.968 — —

07/29/94 28.70 — 0.00 27.446 — — 0.001 0.356

08/15/94 44.54 24.00 0.00 27.553 3.083 0.991 -0.001 0.396

08/16/94 37.96 22.00 0.00 27.606 2.302 0.988 -0.001 0.900

08/17/94 36.70 23.90 0.00 27.712 3.191 0.998 -0.001 0.583

08/22/94 34.86 23.00 0.00 27.606 2.605 0.972 — —

08/23/94 31.94 — 0.00 27.500 — — 0.000 -0.217

09/08/94 32.06 22.30 0.00 27.473 1.877 0.956 — —

09/15/94 34.00 — 0.00 27.553 — — 0.087 0.979

10/24/94 26.08 — 0.00 27.713 — — 0.002 0.633

10/26/94 27.68 16.40 0.00 27.712 0.794 0.982 — —

10/28/94 26.22 — 0.00 28.085 1.195 0.982 0.000 -0.218

11/01/94 18.28 — 0.00 27.872 1.082 0.811 0.012 0.706

11/23/94 15.40 7.90 0.00 27.659 1.209 0.979 0.000 —

11/28/94 8.40 — 0.00 27.766 — — -0.002 0.672

12/20/94 7.40 — 0.00 27.446 0.905 0.984 — —

02/24/95 13.66 — 0.63 27.340 0.966 0.977 -0.010 0.886

03/27/95 21.30 22.90 2.54 26.170 1.716 0.840 0.012 0.999

04/17/95 16.54 13.00 0.00 27.925 1.517 0.982 0.012 0.991

05/17/95 31.34 16.20 0.00 20.000 6.063 0.999 0.012 0.986

06/22/95 33.16 18.80 0.00 20.000 7.020 0.999 0.000 -0.262

07/11/95 29.74 21.10 0.00 19.893 2.702 0.942 0.011 0.875

09/07/95 30.28 — 0.00 19.893 3.087 0.988 — —

Table 28. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control site 

SM—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)
38 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 29. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M1—Continued]

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/26/93 29.92 20.10 0.00 28.484 7.245 0.959 — —

07/27/93 29.98 — 0.00 47.553 0.377 -0.105 0.000 -0.333

07/28/93 23.78 — 0.00 47.659 -1.658 0.984 -0.002 -0.287

07/29/93 22.70 19.10 0.00 28.453 1.973 0.877 — —

07/30/93 27.94 19.60 0.00 28.617 2.250 0.955 — —

07/31/93 34.20 20.10 0.00 27.792 4.625 0.928 — —

08/02/93 35.86 22.10 0.00 28.510 3.897 0.946 — —

08/04/93 27.20 20.60 0.00 28.377 4.086 0.955 — —

08/12/93 30.72 19.50 0.00 28.324 4.110 0.962 — —

08/23/93 34.88 20.30 0.00 28.298 3.156 0.992 — —

09/07/93 30.86 20.00 0.00 28.032 3.493 0.927 — —

09/08/93 28.12 19.90 21.95 30.239 -0.061 -0.301 — —

09/10/93 26.16 19.00 0.00 30.239 1.796 0.968 -0.001 -0.009

09/13/93 28.04 18.50 0.00 29.920 3.570 0.997 — —

09/14/93 28.04 — 0.00 29.920 — — 0.004 0.476

09/15/93 20.32 16.70 0.00 28.936 2.237 0.986 — —

09/27/93 31.70 17.20 0.00 28.032 2.891 0.977 — —

10/06/93 23.12 16.00 0.00 28.404 1.780 0.982 — —

10/19/93 25.16 15.80 0.00 48.217 2.668 0.973 -0.001 0.033

10/21/93 22.62 — 17.94 36.781 0.342 0.772 0.001 -0.201

10/22/93 24.58 — 17.15 37.526 0.215 0.102 0.001 -0.319

10/25/93 28.40 — 11.75 48.723 3.978 0.931 -0.026 0.436

10/27/93 26.42 — 12.54 40.691 2.130 0.899 -0.002 0.732

10/29/93 25.32 — 16.83 36.968 1.915 0.979 -0.005 -0.242

11/01/93 22.64 — 12.94 19.122 0.811 0.459 -0.006 -0.049

11/05/93 23.78 — 10.40 41.702 1.020 0.919 0.005 0.741

11/18/93 16.88 9.30 17.46 36.489 0.667 0.878 0.001 0.914

11/30/93 16.42 7.60 15.32 28.563 0.106 0.018 0.002 -0.148

01/10/94 6.02 — 9.84 42.234 -0.174 0.845 0.006 0.891

01/20/94 15.94 — 10.80 42.127 — — 0.014 0.374

02/02/94 14.22 — 12.70 19.787 — — -0.001 -0.150

02/04/94 15.36 — 11.75 19.787 0.082 0.499 — —

02/16/94 19.02 — 10.80 20.213 — — 0.007 0.934

02/23/94 15.78 — 15.88 17.021 0.421 0.910 — —

03/02/94 22.92 — 14.92 17.872 — — 0.021 0.661

03/04/94 21.90 — 13.65 18.723 0.264 0.780 — —

03/14/94 25.02 — 7.86 22.181 — — 0.030 0.415

03/16/94 14.94 10.80 7.78 22.659 0.396 0.867 — —

03/28/94 25.28 — 6.91 23.191 — — 0.044 0.521

04/11/94 21.96 11.40 0.00 27.446 0.457 0.747 — —

04/13/94 25.95 — 10.95 20.638 — — 0.005 0.916

04/29/94 19.28 12.90 0.00 27.712 2.461 0.961 — —

05/02/94 25.88 — 0.00 27.712 — — 0.011 0.974

05/11/94 25.58 15.60 0.00 27.792 4.132 0.994 — —

Table 29. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M1, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]
Tables 39

05/18/94 26.22 — 0.00 27.500 — — 0.000 -0.270

05/20/94 28.28 15.40 0.00 27.500 2.830 0.992 — —

06/06/94 26.98 17.40 0.00 27.553 4.245 0.965 — —

06/08/94 17.98 — 0.00 27.819 — — 0.003 0.995

06/20/94 31.50 17.90 0.00 27.686 3.398 0.946 0.005 0.620

06/22/94 32.74 18.00 0.00 27.553 2.921 0.998 -0.001 -0.083

06/23/94 27.30 18.50 0.00 27.872 2.788 0.996 0.000 -0.004

06/24/94 28.50 27.70 0.00 27.553 2.918 0.941 0.000 -0.321

06/27/94 32.52 18.70 0.00 27.553 5.802 0.998 0.059 0.977

06/29/94 27.78 18.30 0.00 27.653 6.623 0.994 0.004 0.657

07/01/94 33.82 19.30 0.00 27.579 6.527 0.975 — —

07/14/94 34.18 20.30 0.00 28.032 7.041 0.960 0.009 0.753

07/27/94 30.02 19.20 0.00 27.579 6.291 0.997 — —

07/29/94 32.66 — 0.00 28.191 — — 0.004 0.989

08/15/94 33.20 22.40 0.00 27.872 5.710 0.981 0.004 0.686

08/16/94 31.68 22.40 2.06 26.595 2.243 0.996 -0.001 0.527

08/17/94 29.24 17.70 0.00 27.659 3.627 0.988 0.000 0.085

08/22/94 26.94 19.20 0.00 27.819 3.240 0.982 — —

08/23/94 28.44 — 0.00 27.819 — — 0.112 0.976

09/08/94 26.92 18.20 0.00 27.526 4.137 0.994 — —

09/15/94 24.55 — 0.00 27.500 — — 0.000 0.990

10/24/94 23.22 — 0.00 27.872 — — 0.000 -0.255

10/26/94 24.40 14.20 0.00 27.526 0.968 0.899 — —

10/28/94 22.36 — 13.65 18.723 1.209 0.999 -0.001 0.748

11/01/94 15.18 — 16.03 16.915 1.785 0.983 -0.014 0.514

11/23/94 12.48 6.70 5.48 23.830 0.567 0.904 — —

11/28/94 11.26 — 20.96 13.617 — — 0.002 0.903

12/20/94 8.38 — 17.54 15.904 1.206 0.998 — —

03/27/95 18.44 — 27.94 8.830 0.220 0.877 -0.003 0.071

05/17/95 25.82 — 18.57 7.979 0.329 0.884 0.008 0.678

07/11/95 26.48 — 1.27 19.361 0.960 0.918 0.035 0.630

Table 29. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M1—Continued]

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)
40 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

]

Table 30. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M2—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 30.50 20.10 0.00 46.569 6.779 0.988 0.008 -0.052

07/26/93 29.32 20.10 0.00 28.138 5.580 0.968 0.000 -0.481

07/27/93 29.02 — 0.00 46.595 0.759 0.494 0.007 0.908

07/28/93 24.98 — 0.00 47.127 2.599 0.981 -0.004 -0.085

07/29/93 23.60 19.40 0.00 27.602 3.138 0.915 — —

07/30/93 28.60 19.50 0.00 27.234 3.603 0.982 — —

07/31/93 34.64 19.60 0.00 27.207 5.895 0.961 — —

08/02/93 36.10 21.20 0.00 27.872 5.192 0.975 — —

08/04/93 28.02 20.80 0.00 27.686 5.296 0.975 — —

08/12/93 33.40 — 0.00 27.500 5.436 0.992 — —

08/23/93 34.44 20.40 0.00 27.446 4.680 0.998 — —

09/07/93 31.10 20.00 0.00 27.447 3.453 0.998 — —

09/08/93 29.90 19.80 23.73 29.228 1.305 0.957 — —

09/10/93 26.50 19.40 0.00 27.127 3.355 0.947 0.001 -0.248

09/13/93 28.62 18.90 0.00 29.202 3.727 0.983 — —

09/14/93 28.62 — — 29.202 — — 0.003 0.113

09/15/93 20.40 17.90 0.00 29.255 2.679 0.938 — —

09/27/93 31.64 16.90 0.00 27.872 2.813 0.982 — —

10/06/93 22.82 16.40 0.00 27.712 2.750 0.923 — —

10/19/93 24.92 16.20 0.00 39.148 1.929 0.834 0.006 0.739

10/21/93 22.54 — 15.08 38.218 -1.079 0.354 0.000 -0.329

10/22/93 25.56 — 15.91 39.148 0.628 0.806 0.002 -0.248

10/25/93 28.26 — 11.59 40.319 1.455 0.801 0.007 -0.067

10/27/93 26.82 — 9.69 42.287 0.526 0.728 0.001 0.004

10/29/93 25.54 — 14.13 39.468 0.891 0.945 0.003 -0.269

11/05/93 23.78 — 7.03 43.407 1.542 0.906 -0.002 0.086

11/18/93 15.62 8.00 18.65 35.053 0.333 0.794 0.000 -0.265

11/30/93 15.06 7.60 12.22 32.234 0.342 0.759 0.000 -0.298

01/10/94 7.18 5.80 7.14 43.829 0.045 -0.125 0.005 0.473

01/20/94 15.58 — 7.14 43.936 — — 0.000 -0.333

02/02/94 13.78 — 8.73 20.957 — — 0.008 0.931

02/04/94 14.68 — 9.05 21.489 0.004 -0.332 — —

02/16/94 18.18 — 14.13 18.298 — — 0.003 0.947

02/23/94 17.70 — 13.81 18.085 0.149 0.902 — —

03/02/94 23.34 — 12.14 19.361 — — 0.003 0.438

03/04/94 22.08 — 11.59 19.468 0.051 -0.058 — —

03/14/94 23.84 — 6.35 23.191 — — 0.004 0.936

03/16/94 15.64 10.90 4.45 24.255 0.015 -0.324 — —

03/28/94 25.44 — 6.35 23.191 — — 0.000 0.860

04/11/94 24.78 11.50 0.00 27.287 0.335 0.438 — —

04/13/94 25.80 — 7.78 22.127 — — 0.018 0.909

04/29/94 19.36 13.10 0.00 27.181 4.381 0.993 — —

05/02/94 25.30 — 0.00 27.287 — — 0.031 0.987

05/11/94 24.30 15.40 0.00 27.074 3.091 0.969 — —

Table 30. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M2, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]
Tables 41

05/18/94 27.10 — 0.00 27.207 — — 0.003 0.993

05/20/94 27.40 15.20 0.00 27.127 3.885 0.969 — —

06/06/94 26.78 17.20 0.00 27.074 6.473 0.993 — —

06/08/94 17.64 — 0.00 27.446 — — 0.007 0.972

06/20/94 30.14 18.20 0.00 27.127 7.160 0.930 0.008 0.968

06/22/94 30.98 19.00 0.00 27.154 5.777 0.989 0.009 0.983

06/23/94 28.38 18.00 0.00 27.181 4.811 0.955 0.012 0.915

06/24/94 28.30 17.80 0.00 27.181 5.898 0.994 0.008 0.975

06/27/94 37.68 18.60 0.00 27.234 4.404 0.979 0.003 -0.124

06/29/94 28.40 18.60 0.00 27.446 3.553 0.992 0.003 0.974

07/01/94 34.66 19.70 0.00 27.181 6.268 0.995 — —

07/14/94 34.30 21.40 0.00 27.606 8.468 0.996 0.007 0.953

07/27/94 28.88 18.90 0.00 27.234 6.481 0.989 — —

07/29/94 32.16 — 0.00 — — — 0.006 0.994

08/15/94 36.82 19.20 0.00 27.287 8.958 0.994 0.002 -0.163

08/16/94 33.96 21.20 0.00 27.287 5.126 0.998 0.007 0.896

08/17/94 32.12 19.50 0.00 27.181 5.182 0.988 0.008 0.986

08/22/94 30.96 20.40 0.00 26.968 3.778 0.995 — —

08/23/94 31.70 — 0.00 26.915 — — 0.005 0.951

09/08/94 26.02 18.70 0.00 26.941 5.243 0.999 — —

09/15/94 26.06 — 0.00 27.127 — — 0.005 0.993

10/24/94 24.28 — 0.00 27.127 — — 0.004 0.997

10/26/94 22.34 14.20 0.00 27.074 3.198 0.971 — —

10/28/94 22.66 — 11.59 19.468 1.471 0.950 0.003 0.605

11/23/94 12.26 7.00 2.30 25.532 1.536 0.996 — —

11/28/94 12.14 — 17.46 15.319 — — 0.005 0.977

02/24/95 14.68 — 19.69 14.042 0.445 0.862 0.052 0.626

03/27/95 20.66 — 25.40 10.106 0.350 0.642 0.008 0.850

04/17/95 13.36 — 13.02 18.298 0.695 0.930 0.022 0.740

05/17/95 28.74 — 15.88 9.149 1.943 0.998 0.032 0.952

06/22/95 34.34 — 5.08 16.702 8.358 1.000 0.038 0.965

07/11/95 27.12 — 0.00 19.787 2.666 0.997 0.048 0.996

09/06/95 34.64 — 0.00 19.787 1.988 0.990 0.339 0.994

Table 30. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M2—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)
42 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 31. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M3—Continued

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 29.82 19.80 0.00 46.329 8.219 0.999 0.012 -0.014

07/26/93 27.62 19.70 0.00 28.191 16.810 0.998 0.003 -0.072

07/27/93 28.66 — 0.00 46.489 0.493 0.083 0.000 -0.113

07/28/93 25.74 — 0.00 46.063 0.815 0.962 0.008 0.240

07/29/93 25.30 19.20 0.00 28.453 2.055 0.864 — —

07/30/93 29.88 19.30 0.00 27.819 5.608 0.986 — —

07/31/93 36.44 19.50 0.00 27.260 4.294 0.996 — —

08/02/93 36.58 21.20 0.00 27.553 4.888 0.982 — —

08/04/93 28.62 20.80 0.00 27.181 4.949 0.982 — —

08/12/93 30.00 — 0.00 27.234 4.965 0.893 — —

08/23/93 33.52 20.40 0.00 27.526 6.168 0.972 — —

09/07/93 31.96 19.60 0.00 27.287 2.733 0.998 — —

09/08/93 31.20 20.40 24.33 29.468 3.918 0.969 — —

09/10/93 27.04 19.60 0.00 29.095 4.548 0.935 -0.004 0.619

09/13/93 29.16 18.90 0.00 29.228 5.915 0.988 — —

09/14/93 29.16 — 0.00 29.228 — — 0.006 0.526

09/15/93 20.24 18.00 0.00 27.712 4.808 0.896 — —

09/27/93 30.88 17.00 0.00 27.420 2.015 0.991 — —

10/06/93 22.80 16.40 0.00 27.500 3.450 0.977 — —

10/19/93 24.64 16.10 0.00 38.936 2.435 0.965 0.008 0.965

10/21/93 23.50 — 15.32 38.085 0.630 0.961 0.001 -0.113

10/22/93 25.60 — 13.93 38.617 0.970 0.944 -0.005 -0.040

10/25/93 29.12 — 14.29 39.361 2.415 0.936 0.001 -0.294

10/27/93 26.98 — 9.68 41.914 1.845 0.872 0.003 0.783

10/29/93 24.72 — 13.34 38.829 2.194 0.929 -0.025 0.258

11/05/93 21.42 — 6.15 43.083 1.126 0.718 0.005 0.415

11/18/93 15.26 8.20 17.15 37.234 0.568 0.963 0.001 0.116

11/30/93 14.48 7.60 11.75 32.446 0.296 0.706 0.003 0.463

01/10/94 7.60 — 7.14 43.404 0.100 -0.289 0.001 -0.074

01/20/94 16.12 — 6.67 43.404 — — 0.039 0.415

02/02/94 13.96 — 8.89 20.851 — — 0.000 0.808

02/04/94 15.28 — 8.89 21.064 0.198 0.709 — —

02/16/94 18.52 — 8.81 20.957 — — 0.036 0.756

02/23/94 16.68 — 13.33 18.510 0.422 0.918 — —

03/02/94 24.28 — 11.43 19.574 — — 0.008 0.616

03/04/94 21.94 — 10.00 20.425 0.280 0.993 — —

03/14/94 24.18 — 5.72 23.404 — — 0.028 0.413

03/16/94 16.12 11.00 5.40 23.617 0.423 0.882 — —

03/28/94 24.78 — 5.72 23.191 — — 0.003 0.529

04/11/94 24.30 12.00 0.00 27.074 1.130 0.925 — —

04/13/94 25.20 — 8.62 22.234 — — 0.002 0.952

04/29/94 17.86 12.80 0.00 26.861 5.140 0.956 — —

05/02/94 25.62 — 0.00 27.021 — — -0.001 0.597

Table 31. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M3, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]
Tables 43

05/11/94 21.10 14.90 0.00 26.968 5.597 0.989 — —

05/18/94 30.14 — 0.00 27.101 — — 0.002 0.978

05/20/94 26.90 15.00 0.00 26.968 4.442 0.992 — —

06/06/94 27.16 17.40 0.00 26.994 3.404 0.956 — —

06/08/94 16.42 — 0.00 27.127 — — 0.010 0.856

06/20/94 31.58 20.00 0.00 27.021 2.883 0.999 0.009 0.973

06/22/94 30.34 19.70 0.00 26.968 3.388 0.998 0.001 -0.021

06/23/94 29.54 18.30 0.00 27.127 2.227 0.954 0.002 0.937

06/24/94 29.54 17.70 0.00 27.074 1.950 0.868 0.001 -0.050

06/27/94 36.42 18.80 0.00 27.234 5.190 0.987 0.009 0.959

06/29/94 29.42 18.30 0.00 26.968 2.890 0.943 0.007 0.984

07/01/94 34.78 19.20 0.00 26.702 3.923 0.992 — —

07/14/94 31.68 20.00 0.00 27.606 5.862 0.988 0.006 0.890

07/27/94 24.62 18.80 0.00 26.968 5.449 0.988 — —

07/29/94 32.50 — 0.00 27.340 — — 0.007 0.995

08/15/94 34.36 17.30 0.00 27.234 4.176 0.982 0.037 0.878

08/16/94 33.72 22.20 0.00 27.127 2.816 0.998 0.001 0.773

08/17/94 31.48 20.60 0.00 27.181 3.683 0.982 0.002 0.948

08/22/94 28.92 20.40 0.00 27.500 2.955 0.972 — —

08/23/94 28.58 — 0.00 27.021 — — 0.004 0.993

09/08/94 25.16 18.10 0.00 26.861 3.774 0.938 — —

09/15/94 24.30 — 0.00 26.808 — — 0.002 0.901

10/24/94 23.30 — 0.00 26.649 — — 0.002 0.963

10/26/94 22.62 14.00 0.00 26.941 1.844 0.938 — —

10/28/94 22.56 — 10.00 20.425 0.719 0.889 0.001 0.526

11/01/94 14.32 — 13.34 18.191 1.090 0.940 0.000 -0.272

11/23/94 11.60 6.60 1.98 25.532 0.547 0.773 — —

11/28/94 11.76 19.05 14.47 17.393 — — 0.007 0.970

12/20/94 8.60 — 14.29 17.393 0.939 0.996 — —

02/24/95 14.56 — 19.05 14.468 0.477 0.982 0.043 0.808

04/17/95 14.34 — 13.34 18.298 0.540 0.940 0.037 0.957

06/22/95 34.48 — 4.13 17.127 0.589 0.897 0.050 0.685

09/06/95 34.14 — 0.00 19.681 1.486 0.802 1.069 0.864

Table 31. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

M3—Continued

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2

/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2

/day)

CH4 adjusted R2 

(g C/m2/day)
44 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 32. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control site 

MF—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/27/93 28.66 22.40 0.00 28.484 6.089 0.999 0.002 0.344

07/28/93 26.04 21.90 0.00 28.590 4.691 0.989 0.002 -0.231

07/29/93 25.40 — 0.00 28.406 2.803 0.888 — —

07/30/93 33.64 21.80 0.00 29.149 6.151 0.965 — —

07/31/93 38.60 22.00 0.00 29.893 5.129 0.998 — —

08/02/93 39.34 24.20 0.00 30.000 6.166 0.982 — —

08/04/93 30.88 23.30 0.00 29.441 6.220 0.982 — —

08/12/93 33.26 23.10 0.00 29.282 4.961 0.996 — —

08/23/93 35.55 — 0.00 30.000 — — 0.038 0.970

09/07/93 30.34 23.30 0.00 29.734 4.264 0.990 — —

09/08/93 36.06 22.50 0.00 29.574 3.741 0.990 — —

09/10/93 30.88 23.20 0.00 31.755 3.986 0.981 — —

09/13/93 35.02 22.10 0.00 31.595 4.894 0.991 — —

09/15/93 24.88 21.00 0.00 30.319 4.412 0.990 — —

09/27/93 34.26 20.50 0.00 29.548 3.238 0.983 — —

10/06/93 24.36 19.40 0.00 28.803 3.200 0.996 — —

10/19/93 24.58 18.50 0.00 29.441 3.180 0.954 0.012 0.976

10/21/93 25.98 18.50 0.00 29.707 2.309 0.991 -0.014 0.280

10/22/93 30.00 17.50 0.00 29.681 1.610 0.975 0.009 0.611

10/25/93 30.26 17.40 0.00 29.521 4.103 0.966 0.018 0.976

10/27/93 29.62 17.40 0.00 29.521 3.250 0.558 0.014 0.958

10/29/93 26.08 16.60 0.00 30.000 1.828 0.987 0.008 -0.059

11/01/93 22.52 — 0.00 29.734 1.060 0.937 0.035 0.985

11/05/93 15.10 — 0.00 29.335 1.539 0.947 0.007 0.971

11/18/93 14.48 9.90 0.00 29.415 2.793 0.993 0.000 -0.330

11/30/93 12.02 8.10 1.75 26.702 0.445 0.702 -0.002 0.480

01/10/94 11.66 7.00 3.18 26.064 1.202 0.985 0.001 0.654

01/20/94 20.58 — 2.06 27.553 — — 0.010 0.945

02/02/94 13.40 — 1.11 28.404 — — 0.001 0.796

02/04/94 17.36 6.60 1.27 27.978 0.110 -0.173 — —

02/16/94 20.44 — 1.51 26.968 — — -0.001 -0.303

02/23/94 17.22 9.00 1.11 27.340 0.102 0.050 — —

03/02/94 26.52 — 0.00 28.085 — — 0.003 0.719

03/04/94 23.30 13.20 0.64 27.340 0.489 0.767 — —

03/14/94 28.64 — 0.00 28.191 — — -0.004 -0.074

03/16/94 16.88 12.70 0.79 27.553 -0.832 0.568 — —

03/28/94 25.80 — 0.79 27.659 — — 0.000 -0.276

04/11/94 25.04 13.90 0.00 27.872 4.793 0.959 — —

04/13/94 25.44 — 0.00 27.234 — — 0.011 0.934

04/29/94 19.28 14.60 0.00 27.101 7.225 0.996 — —

05/11/94 17.54 16.10 0.00 27.473 7.284 0.993 — —

05/20/94 25.26 16.20 0.00 27.367 7.010 0.998 — —

06/06/94 23.00 18.70 0.00 27.446 5.687 0.999 — —

06/09/94 19.36 — 0.00 27.659 — — -0.010 0.503

Table 32. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control 

site MF, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]
Tables 45

06/20/94 32.92 22.30 0.00 26.861 4.418 0.998 -0.002 0.737

06/22/94 39.58 19.70 0.00 27.048 2.717 0.997 0.000 -0.313

06/23/94 33.68 19.80 0.00 27.181 4.749 0.999 0.001 0.463

06/24/94 35.22 22.30 0.00 27.234 5.246 0.992 0.003 0.709

06/27/94 37.26 20.40 0.00 27.127 5.581 0.981 0.000 -0.331

06/29/94 34.22 20.30 0.00 27.340 10.860 0.997 0.000 -0.327

07/01/94 31.76 20.90 0.00 28.085 9.002 0.997 — —

07/14/94 31.36 26.70 0.00 27.606 14.830 0.993 -0.001 -0.256

07/27/94 22.44 21.00 0.00 26.941 12.230 0.999 — —

07/29/94 28.10 — 0.00 27.021 — — 0.000 -0.065

08/15/94 35.42 22.50 0.00 27.127 14.450 0.998 0.000 -0.333

08/16/94 37.70 24.30 0.00 27.340 8.671 0.994 0.001 0.535

08/17/94 39.30 23.40 0.00 26.702 8.870 0.999 0.001 0.161

08/22/94 32.14 18.40 0.00 26.595 9.745 1.000 — —

08/23/94 35.36 — 0.00 26.755 — — 0.004 0.727

09/08/94 22.20 20.60 0.00 27.234 7.522 0.997 — —

09/15/94 42.08 — 0.00 27.021 — — 0.002 0.986

10/24/94 29.76 — 0.00 26.276 — — 0.008 0.942

10/26/94 20.84 15.40 0.00 26.542 7.868 0.993 — —

10/28/94 26.40 — 0.64 27.553 5.868 0.996 0.007 0.803

11/23/94 10.42 7.30 0.00 26.915 2.610 0.995 — —

11/28/94 9.20 — 3.02 25.106 — — 0.000 -0.307

12/20/94 7.80 — 0.95 27.500 2.315 0.909 — —

02/24/95 16.36 — 0.64 27.021 1.939 0.991 -0.004 0.904

03/27/95 24.42 22.30 3.02 25.638 2.149 0.951 0.073 0.997

04/17/95 16.18 13.00 0.00 27.021 1.525 0.384 0.035 0.874

05/17/95 32.52 — 0.00 19.787 2.696 0.987 0.004 0.988

06/22/95 37.34 34.10 0.00 19.574 10.172 0.999 0.009 0.986

07/11/95 28.24 20.70 0.00 20.425 7.985 0.999 0.007 0.988

09/06/95 35.10 — 0.00 20.213 7.424 0.993 0.014 0.938

Table 32. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at control site 

MF—Continued

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)
46 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 33. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

F1, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date Mean temperature (οC)

Soil temperature (οC)Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 28.43 — 27.94 49.467 — — 0.052 0.894

07/28/93 25.00 — 28.73 29.255 — — 1.291 0.811

08/12/93 26.84 — 14.29 38.936 2.636 0.328 3.546 0.551

08/23/93 30.40 — 11.11 41.276 — — 4.874 0.605

09/07/93 31.32 — 19.37 36.516 — — 0.610 0.956

09/21/93 23.04 — 12.94 31.246 — — 0.058 0.879

10/06/93 20.90 — 15.84 35.797 — — 1.412 0.928

10/19/93 21.30 — 16.35 39.255 — — 0.549 0.934

11/05/93 22.42 — 16.35 37.021 — — 0.044 -0.155

11/19/93 17.28 — 53.02 35.531 — — 0.019 0.969

12/01/93 16.86 — 52.71 35.319 — — 0.063 0.674

01/05/94 9.04 — 24.29 16.808 — — 0.023 0.273

01/20/94 15.92 — 25.72 33.617 — — 0.161 0.799

02/02/94 14.22 — 28.73 32.340 — — 0.230 0.475

02/16/94 19.52 — 27.62 31.701 — — 0.109 0.749

03/02/94 24.22 — 29.05 30.638 — — 0.055 0.870

03/14/94 27.66 — 26.99 32.766 — — 0.074 0.883

03/28/94 27.58 — 22.70 35.957 — — 0.016 0.656

04/13/94 25.78 — 16.99 38.457 — — 4.201 0.844

05/18/94 18.86 — 15.76 37.659 — — 2.389 0.747

06/09/94 18.00 — 22.30 34.946 — — 0.206 0.644

06/29/94 37.52 — 21.59 36.170 — — 0.523 0.688

07/14/94 39.64 — 6.11 45.053 — — 0.119 0.641

07/29/94 32.54 — 18.49 36.063 — — 1.030 0.816

08/23/94 29.96 — 21.75 32.978 — — 0.008 0.877

09/15/94 31.78 — 12.30 40.000 — — 0.666 0.956

10/24/94 22.90 — 4.84 44.255 — — 0.007 0.352

11/28/94 12.22 — 18.10 36.808 — — 0.013 0.311

12/08/94 12.04 — 15.56 36.063 0.301 0.023 — —

12/20/94 7.88 — 18.73 34.840 0.669 0.940 — —

03/27/95 18.84 — 34.29 24.149 0.058 -0.283 0.154 0.944

05/17/95 30.18 — 23.32 24.255 -0.086 0.000 0.252 0.868

07/11/95 28.80 28.80 8.26 34.468 3.250 0.964 0.101 0.270
Tables 47

Table 34. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

F2, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 28.56 — 25.40 51.489 — — 0.516 0.938

07/28/93 25.00 — 24.13 32.021 — — 0.134 0.980

08/12/93 27.32 — 11.27 41.648 -0.252 -0.267 0.126 0.928

08/23/93 30.45 — 8.26 36.808 — — 0.030 0.652

09/07/93 27.35 — 17.30 38.377 — — 0.545 0.965

09/21/93 23.00 — 11.43 34.149 — — 0.131 0.937

10/06/93 20.68 — 13.73 38.031 — — 0.004 0.984

10/19/93 21.40 — 15.40 39.787 — — 0.296 0.887

11/05/93 23.68 — 14.61 40.053 — — 0.027 0.970

11/19/93 16.98 — 57.15 38.297 — — 0.047 0.751

12/01/93 16.54 — 56.04 37.533 — — 0.028 0.736

01/05/94 8.98 — 22.86 20.904 — — 0.083 0.750

01/20/94 16.50 — 22.30 35.904 — — 0.190 0.931

02/02/94 13.28 — 24.29 34.787 — — 0.000 -0.333

02/16/94 19.42 — 26.35 33.617 — — 0.159 0.842

03/02/94 25.06 — 28.10 32.553 — — 0.019 0.726

03/14/94 28.02 — 20.96 37.021 — — 0.601 0.943

03/28/94 26.34 — 20.00 37.978 — — 0.042 0.659

04/13/94 26.98 — 15.24 40.851 — — 1.061 0.854

05/18/94 19.36 — 12.86 40.265 — — 0.309 0.818

06/09/94 18.22 — 20.72 37.659 — — 0.526 -0.167

06/29/94 37.52 — 16.67 38.723 — — 0.844 0.749

07/14/94 31.88 — 3.81 46.542 — — 0.075 0.079

07/29/94 43.40 — 16.19 37.872 — — 0.768 0.934

08/23/94 32.60 — 19.69 35.531 — — 0.141 0.653

09/15/94 32.58 — 8.18 42.606 — — 0.154 0.840

10/24/94 23.72 — 3.65 45.957 — — 0.011 0.842

11/28/94 13.86 — 13.34 39.574 — — 0.036 0.997

12/08/94 11.96 — 10.95 38.297 0.713 0.939 — —

02/24/95 13.80 — 27.31 29.787 0.910 0.997 0.045 0.523

03/27/95 15.58 — 29.69 26.489 0.556 0.044 0.171 0.962

04/17/95 15.62 — 20.96 33.297 0.454 0.843 0.211 0.314

05/17/95 27.70 — 22.23 26.808 0.934 0.920 0.071 0.963

06/22/95 37.38 — 11.11 33.829 7.550 0.975 0.523 0.934

07/11/95 27.48 — 5.24 36.808 4.410 0.981 0.148 0.950

09/06/95 35.43 — 7.46 35.425 1.830 0.989 0.010 0.865
48 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 35. Mean chamber temperature, soil temperature, water depth, head space, CO2 fluxes, CH4 fluxes, and adjusted R2 for flux regression at pond site 

F3, Twitchell Island, California

[Missing data are denoted by —. οC, degrees Celsius; g C/m2/day, grams of carbon per square meter per day]

Date

Mean 

temperature 

(

οC)

Soil 

temperature 

(

οC)

Water depth 

(centimeters)

Head space

 (liters)

CO2 flux

(g C/m2/day)

CO2 adjusted R2 

(g C/m2/day)

CH4 flux

 (g C/m2/day)

CH4 adjusted R2 

(g C/m2/day)

07/14/93 30.05 — 24.29 53.084 — — 1.537 0.963

07/28/93 25.00 — 22.70 33.829 — — -0.196 0.673

08/12/93 27.40 — 11.43 40.638 -0.465 -0.301 -0.015 0.303

08/23/93 30.90 — 8.41 35.797 — — 0.856 0.719

09/07/93 28.78 — 14.45 39.867 — — 0.114 0.866

09/21/93 23.80 — 11.43 42.978 — — 0.598 0.815

10/06/93 21.75 — 11.11 39.547 — — 0.001 0.996

10/19/93 22.58 — 15.00 41.010 — — 0.136 0.889

11/05/93 24.50 — 14.60 40.531 — — 0.880 0.590

11/19/93 17.54 — 56.99 38.191 — — 0.011 0.220

12/01/93 16.56 — 56.20 37.659 — — -0.001 -0.177

01/05/94 8.78 — 23.02 20.851 — — 0.141 0.626

01/20/94 17.72 — 22.07 36.276 — — 0.204 0.956

02/02/94 13.24 — 24.13 34.893 — — 0.055 -0.194

02/16/94 18.84 — 24.29 34.042 — — 0.020 0.031

03/02/94 25.04 — 26.65 33.191 — — 0.124 0.798

03/14/94 26.80 — 23.02 36.170 — — 0.031 0.518

03/28/94 26.10 — 17.78 38.723 — — 0.229 0.210

04/13/94 27.20 — 15.08 41.276 — — 0.246 0.696

05/18/94 18.94 — 11.03 40.425 — — 0.948 0.739

06/09/94 17.96 — 18.81 39.308 — — 0.316 0.932

06/29/94 41.16 — 16.99 39.148 — — 0.043 0.981

07/14/94 31.28 — 0.16 47.446 — — 0.153 0.976

07/29/94 32.70 — 13.97 38.297 — — 0.446 0.991

08/23/94 29.90 — 16.12 36.063 — — 0.281 0.983

09/15/94 31.00 — 6.83 42.127 — — 0.484 0.988

10/24/94 23.22 — 0.00 46.276 — — 0.417 0.990

11/28/94 12.50 — 9.84 39.893 — — 0.144 0.863

12/08/94 10.60 — 11.43 38.297 2.253 0.701 — —

12/20/94 8.10 — 13.85 37.287 0.984 0.974 — —

02/24/95 12.90 — 25.40 30.000 1.834 0.960 0.123 0.848

04/17/95 15.50 — 19.05 33.829 1.466 0.921 0.379 0.389

06/22/95 37.24 — 7.30 34.255 3.839 0.996 0.177 0.980

09/06/95 31.40 — 3.02 35.957 5.268 0.999 0.132 0.978
Tables 49

Table 36. Biomass measurements based on vegetation sampling on October 13, 1993, Twitchell Island, California

[Missing data are denoted by —]

1Grams carbon per square centimeter:

 S: Average = 0.061; standard deviation = 0.025

 M: Average = 0.070; standard deviation = 0.026

 F: Average = 0.071; standard deviation = 0.012

Sample

Grams 

corrected dry 

weight

Mean

Grams biomass 

per square

 centimeter

Percent carbon Average 

percent

carbon

Grams

 carbon

Grams carbon

per square 

centimeter1 Rep 1 Rep 2

S1 816.740 608.642 0.164 38.33 39.02 38.68 315.874 0.085

S2 688.080 608.642 — 27.27 34.78 31.03 213.477 0.057

S3 852.050 — — 37.53 39.10 38.32 326.463 0.088

S4 402.660 — — 40.12 39.54 39.83 160.379 0.043

S5 283.680 — — 42.43 41.62 42.03 119.217 0.032

M1 915.150 648.697 0.175 40.65 40.17 40.41 369.812 0.100

M2 540.700 — — 39.99 38.83 39.41 213.090 0.057

M3 541.000 — — 39.93 39.68 39.81 215.345 0.058

M4 466.430 — — 38.98 39.89 39.44 183.937 0.049

M5 960.000 — — 40.44 41.04 40.74 391.104 0.105

M6 468.900 — — 37.67 39.28 38.48 180.409 0.049

F1 650.100 629.800 0.169 — — — — —

F2 525.000 — — 42.14 42.56 42.35 222.338 0.060

F3 538.600 — — 42.88 42.77 42.83 230.655 0.062

F4 739.000 — — 41.70 41.52 41.61 307.498 0.083

F5 696.300 — — 43.39 42.83 43.11 300.175 0.081
50 Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, California, 1992-95

Table 37. Biomass measurements based on vegetation sampling on October 25, 1994, Twitchell Island, California

1Grams carbon per square centimeter:

 S: Average = 0.069; standard deviation = 0.014

 M: Average = 0.066

 F: Average = 0.160; standard deviation = 0.028

Table 38. Biomass measurements based on vegetation sampling on July 25, 1995 (pond S), and October 31, 1995 (ponds M and F), Twitchell Island, 

California

[Missing data are denoted by —]

1Grams carbon per square centimeter:

 Pond S: Average = 0.041; standard deviation = 0.007

 Pond M: Average = 0.140; standard deviation = 0.041

 Pond F: Average = 0.208; standard deviation = 0.039

Sample

Grams 

corrected dry 

weight

Percent carbon Average

percent

carbon

Grams

 carbon

Grams carbon

per square 

centimeter1 Rep 1 Rep 2 Rep 3

S1 736.7 41.37 40.61 42.29 41.42 305.2 0.082

S2 486.2 40.02 41.43 41.7 41.05 199.6 0.054

S3 609.3 41.86 43.5 43.13 42.83 261.0 0.070

M1 827.5 41.56 41.39 41.68 41.54 343.8 0.093

M2 585.2 38.57 39.5 39.59 39.22 229.5 0.062

M3 458.1 41.3 41.07 40.8 41.06 188.1 0.051

M4 566.6 40.16 39.7 39.78 39.88 226.0 0.061

F1 1275.2 42.57 43.32 43.41 43.10 549.6 0.148

F2 1192.8 43.12 43.59 43.54 43.42 517.9 0.139

F3 1589.8 44.58 45.17 44.94 44.90 713.8 0.192

Sample

Grams 

corrected 

dry 

weight

Mean

Grams 

biomass 

per 

square 

centimeter

Standard 

error Percent carbon

Average 

percent 

carbon

Grams 

carbon

Grams 

carbon 

per 

square 

centimeter Rep 1 Rep 2 Rep 3 Rep 4 Rep 5 Rep 6 Rep 7 Rep 8 Rep 9 1

S1 317.9 — — — 42.11 42.18 42.99 39.95 40.98 42.48 — — — 41.78 132.84 0.036

S2 409.3 352.8 949.3 76.764 43.78 44.1 44.67 — — — — — — 44.18 180.85 0.049

S3 331.1 — — — 42.24 41.62 41.81 — — — — — — 41.89 138.68 0.037

M1 1070.1 — — — 43.17 43.73 42.95 43.28 — — — — — 43.28 463.18 0.125

M2 1163.5 1333.3 3588.0 587.242 37.01 36.24 32.67 33.64 — — — — — 34.89 405.93 0.109

M3 1766.5 — — — 43.6 42.89 35.81 34.21 — — — — — 39.13 691.17 0.186

F1 1985.8 — — — 31.48 32.36 31.95 35.35 31.97 — — — — 32.62 647.82 0.174

F2 2356.5 2072.6 5577.3 391.489 42.03 42 41.05 41.1 40.59 37.85 39.05 36.58 36.17 39.60 933.22 0.251

F3 1875.4 — — — 44.95 45.29 41.66 41.91 33.44 35.55 32.81 38.58 39.27 736.55 0.198