BOREAS TGB-01/TGB-03 Water Table and Peat Temperature Data over the NSA

Summary

The BOREAS TGB-01 and TGB-03 teams collected several data sets that contributed 
to understanding the measured trace gas fluxes over sites in the NSA.  This data 
set contains continuous and manual measurements of water level, air and soil 
temperatures at the four subsites within the NSA Tower Fen site complex.  The 
measurements were taken to understand the thermal and hydrological gradients 
associated with each plant community present in the fen.  Measurements were 
taken from May to September 1994 and May to October 1996.  The data are provided 
in tabular ASCII files.

Table of Contents

   *  1 Data Set Overview
   *  2 Investigator(s)
   *  3 Theory of Measurements
   *  4 Equipment
   *  5 Data Acquisition Methods
   *  6 Observations
   *  7 Data Description
   *  8 Data Organization
   *  9 Data Manipulations
   *  10 Errors
   *  11 Notes
   *  12 Application of the Data Set
   *  13 Future Modifications and Plans
   *  14 Software
   *  15 Data Access
   *  16 Output Products and Availability
   *  17 References
   *  18 Glossary of Terms
   *  19 List of Acronyms
   *  20 Document Information

1. Data Set Overview

1.1 Data Set Identification

BOREAS TGB-01/TGB-03 Water Table and Peat Temperature Data over the NSA

1.2 Data Set Introduction

Trace Gas Biogeochemistry Teams 1 and 3 (TGB-01 and TGB-03) collected automated 
and manual water table, surface fluctuations, and thermal profile measurements 
at the Northern Study Area (NSA) Tower Fen (TF) site.  These measurements 
complement the Net Ecosystem Exchange (NEE) measurements to help understand the 
environmental controls on NEE. Measurements were made from the period of snow 
melt and thaw through the full growing season to the fall freeze.

1.3 Objective/Purpose

Continuous measurements of water level and air and soil temperatures were taken 
to understand the thermal and hydrological gradients associated with each plant 
community.  Measurements were taken at the four subsites within the fen in the 
NSA.  The locations represent the range of plant communities, water chemistry, 
and peatland types found in northern peatlands, including bog, rich fen, poor 
fen, and collapse scar (pH ranges from 3.8 to 7.2).  

1.4 Summary of Parameters and Variables

The water table level, surface fluctuations, and peat temperatures were measured 
at four locations in the NSA TF site.  The water table and peat temperatures 
were measured at multiple depths for each subsite studied.

1.5 Discussion

NEE was measured at four subsites in the NSA fen, designated as collapse bog 
(CB), collapse fen (CF), TF and Zoltai fen (ZF).  Each collar location is 
further designated by a spur (1, 2, 3, or 4) along the boardwalk at each subsite 
and by the microtopography or dominant ground cover of the collar location: 
pal=palsa, hk=hummock, hw=hollow, lwn=lawn, moat=open water at the edge of the 
collapse scars, b_moss=brown moss, sph=sphagnum, and lich=lichen. Continuous 
water table and temperatures were recorded at each of the subsites to accompany 
the NEE measurements.  Temperatures of the air, 5-cm, 10-cm, 20-cm, and 50-cm 
peat depth were measured at each subsite.  Temperatures correspond to the collar 
location at the subsite.  In cases where the continuous data were missing, 
manual soil temperatures were recorded.  Continuous water level measurements 
were taken at each subsite and are designated by the subsite abbreviation and 
the number of the spur (e.g., CBWL1=collapse bog, water level, spur 1).

1.6 Related Data Sets

BOREAS TGB-04 Substrate Water Table and Sediment Temperature
BOREAS TGB-01/TGB-03 NEE Data over the NSA Fen 

2. Investigator(s)

2.1 Investigator(s) Name and Title

Dr. Timothy R. Moore
Professor, Geography Department
McGill University

2.2 Title of Investigation

Carbon Dioxide and Methane Exchanges Between Wetland and Upland Soils and the 
Atmosphere.

2.3 Contact Information

Contact 1
---------
Dr. Tim R. Moore
Department of Geography
Montreal, Quebec  
(514) 398-4961
moore@felix.geog.mcgill.ca

Contact 2
---------
Dr. Jill Bubier
Institute for the Study of Earth, Oceans, and Space
Complex Systems Research Center
University of New Hampshire
Durham, NH
(603) 862-4208
(603) 862-0188 (fax)
jill.bubier@unh.edu

Contact 3
Sara Conrad
Raytheon STX Corporation
NASA GSFC
Greenelt, MD 
(301) 286-2624
(301) 286-0239
Sara.Golightly@gsfc.nasa.gov

3. Theory of Measurements

Water Table and Surface Fluctuation:  A potentiometer (variable resistor) 
attached to a float determines the voltage measured by the datalogging device.  
The potentiometer is calibrated for 1 mV = 1mm of float movement.  A datalogger 
measures this voltage. 

Temperature Profiles:  Copper-constantan thermocouple wire induces a current 
between the two dissimilar metals according to the temperature at the junction 
of the two wires.  By placing these junctions at known depths along a rod driven 
into the ground, a temperature profile can be measured by a datalogger, if the 
temperature of the opposite junction is known.  This temperature is known by a 
direct measurement from the datalogger.  To permit all temperatures to be 
measured by one datalogger, a multiplexer was used to make more measurements 
than the datalogger alone would allow. 

4. Equipment

4.1 Sensor/Instrument Description

Instrumentation at all four sites included Campbell Scientific CR10 dataloggers, 
Campbell Scientific AM416 multiplexers, and 20 turn potentiometers.  
Multiplexers were used to measure an array of thermocouple rods measuring 
temperature profiles at several locations within each site.  Potentiometers were 
attached to floats within wells dug into the wetlands to measure the 
fluctuations of water tables.  Surface level fluctuations (where made) used the 
same method, with the beaded cable connected to a bog shoe that sat on the 
wetland surface and moved up and down with the surface.  All data were collected 
every 1 minute and averaged and saved by the datalogger every 30 minutes.

Continuous water table measurements were made with a float and counter weight 
attached to a wheel and a potentiometer mounted on a platform that rested on top 
of a wooden post anchored in the clay below the peat.  The potentiometer was 
wired to either a CR10 or CR7 datalogger (Campbell Scientific, Inc., Logan, 
Utah) and recorded the change in water level in mV.  Wells were constructed of 
PVC tubing.   Peat temperatures were recorded with type T thermocouples (copper-
constantan) attached at four levels (5, 10, 20, and 50 cm) to wooden stakes and 
inserted into the peat during the fall of 1995.  The thermocouples were wired to 
either CR10 or CR7 dataloggers and calibrated to reference temperatures.

4.1.1 Collection Environment

Samples were collected under all environmental conditions.

4.1.2 Source/Platform

Ground-mounted datalogger and multiplexers.  Water level recorders and surface 
bog shoe supports were mounted on poles driven deeply into the peat to avoid 
vertical movement.  Thermocouple rods were driven into peat at assigned depths.

4.1.3 Source/Platform Mission Objectives

The objective was to collect continuous water table and surface fluctuations and 
thermal profile measurements of four sites near the NSA TF:  TF< ZF, CF, and CB.

4.1.4 Key Variables

Water table measurements referenced to the wetland surface.
Surface fluctuation measurements referenced to arbitrary datum.
Temperature profiles (four measurements) at various locations within each site.

4.1.5 Principles of Operation

Water Table and Surface Fluctuation:  A potentiometer (variable resistor) 
attached to a float determines the voltage measured by the datalogging device.  
The potentiometer is calibrated for 1 mV = 1mm of float movement.  A datalogger 
measures this voltage. 

Temperature Profiles:  Copper-constantan thermocouple wire induces a current 
between the two dissimilar metals according to the temperature at the junction 
of the two wires.  By placing these junctions at known depths along a rod driven 
into the ground, a temperature profile can be measured by a datalogger, if the 
temperature of the opposite junction is known.  This temperature is known by a 
direct measurement from the datalogger.  To permit all temperatures to be 
measured by one datalogger, a multiplexer was used to make more measurements 
than the datalogger alone would allow. 

4.1.6 Sensor/Instrument Measurement Geometry

Water Table:  Referenced to the average wetland surface height, so a measurement 
of 0 represents a water table at the wetland surface, and negative values 
indicate a water table below the wetland surface.  Regular manual measurements 
of water table depth were taken (weekly) for calibration of the electronic 
readings.

Surface Fluctuations:  Measured similarly to water table and referenced to an 
arbitrary datum below the surface determined at the beginning of the measurement 
period.  This was possible because the mounting poles for the water table and 
surface were sufficiently deep into the peat to prevent their movement as well.

Ground Temperatures:  Referenced to the average wetland surface height.  
Measurement depths were set at 5 cm, 10 cm, 20 cm, and 40 cm.

4.1.7 Manufacturer of Sensor/Instrument

Thermocouple wire:  Type T, Supplier Electrosonic

Dataloggers and Multiplexers:  
Campbell Scientific, Canada Corporation
11564-149th street, Edmunton, AB, Canada, T5M 1W7
(403) 454-2505
(403) 454-2655 (fax)

Water Table and Surface Measurement:
Bournes Precision Twenty turn potentiometers manufactured by 
Electrosonic, Inc.
110 Gordon Baker Road
Willowdale, ON, Canada  M2H 3b3

They were enclosed in PVC electrical boxes and connected to aluminum wheels upon 
which beaded cable and a float (or bog shoe) are attached.  The potentiometers 
are calibrated for 1 mV of voltage change = 1 mm of float height change.  These 
water level recorders were manufactured by TGB-04.

4.2 Calibration

Ground Temperatures:  No calibration was necessary becausethe principle of 
induced current from the contact of dissimilar metals applies.

Water Levels and Surface Fluctuations:  Potentiometers and machined aluminum 
wheels were calibrated from previous experiments.  Weekly manual measurements of 
water table depth were taken to ensure proper calibration of the electronic 
measurements. 

4.2.1 Specifications

Ground Temperatures:  Type T thermocouple rated at +/- 0.01 C maximum error.
Water and Surface Levels:  Maximum error of 1 mm. 

4.2.1.1 Tolerance

Ground Temperatures:  Range allowable:  +/-62.5 oC of datalogger temperature (0-
2.5 mV to datalogger).

Water and Surface Levels:  Range allowable:  largely dependent upon length of 
beaded cable (0-2.5 V to datalogger).

4.2.2 Frequency of Calibration

Instruments were calibrated once before field deployment.  Weekly manual 
measurements of ground temperatures and water and surface levels were also 
performed. 

4.2.3 Other Calibration Information

No corrections were required according to the calibration methods described 
above.

5. Data Acquisition Methods

Ground Temperatures:

Four thermocouples were affixed within each thermocouple rod and sealed in a 
waterproof epoxy. Thermocouple wires from each thermocouple rod were wired into 
the Campbell multiplexer to allow for approximately 16-20 separate measurements 
at each site.  The multiplexer was then connected to the CR10 datalogger and a 
reference thermocouple was run between the datalogger and multiplexer to measure 
the multiplexer temperature that served as a reference for all measurements.  
The datalogger was then instructed to use this multiplexer temperature as the 
basis for the calculation of all the temperatures found on the thermocouple rods 
(by differential voltage measurements).

Water Level and Surface Fluctuation Recorders:

The potentiometer varied the voltage measured by the datalogger as the float (or 
bog shoe) on the beaded cable rose and lowered due to water table changes.  The 
datalogger measured this changing voltage, which was easily converted into a 
height change since the potentiometers were calibrated to 1 mV of change being 
equal to 1 mm of vertical water change.

Temperature and water level were measured continuously and averaged every hour 
on the CR10 or CR7 dataloggers.  Manual measurements of air temperature, peat 
temperature, and water table position were made at the same time as the NEE 
measurements.

6. Observations

6.1 Data Notes

None.

6.2 Field Notes

Throughout the summer, there were no unusual occurrences that would interrupt 
the data other than standard maintenance, which could have affected the measured 
parameters for short periods of time (less than 30 minutes).

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

CB collars were located in a small, circular collapse scar (75 m diameter) 
almost completely surrounded by a permafrost peat plateau, behind the generator 
shed.  Three spurs were located perpendicular to the boardwalk.  Spur 1 was 
adjacent to the moat, or open water lagg area; spur 2 was in a hummock-hollow 
area; and spur 3 was in the center of the collapse scar.  In addition to the 
collars in the collapse scar, this subsite had two collars on the palsa (frozen 
peat plateau) adjacent to the collapse scar.  Collar designations were as 
follows:

CB1moat = collapse bog, spur 1, moat
CB2hk = collapse bog, spur 2, hummock
CB2hw = collapse bog, spur 2, hollow
CB3hk = collapse bog, spur 3, hummock
Cbpalmoss = collapse bog, palsa, moss
Cbpallich = collapse bog, palsa, lichen

CF collars were located in a small, linear collapse feature that was east of and 
accessed from the main trail to the tower hut.  Four spurs were located 
perpendicular to the main boardwalk.  Spur 1 was located adjacent to the moat 
spur 2 was in a uniform lawn of Sphagnum riparium spur 3 was in a small treed 
ridge and spur 4 was on the far edge of the collapse scar where the influence of 
groundwater was apparent.  Collar designations were as follows:

CF1moat = collapse fen, spur 1, moat
CF2lwn = collapse fen, spur 2, lawn
CF3hka = collapse fen, spur 3, hummock (a)
CF3hkb = collapse fen, spur 3, hummock (b)
CF4b_moss = collapse fen, spur 4, brown moss
CF4sph = collapse fen, spur 4, sphagnum

TF collars were located along the boardwalk to the micrometeorological tower in 
the NSA fen.  Four spurs were located perpendicular to the main boardwalk.  Spur 
1 was just beyond the moat at the beginning of the boardwalk in a treed area of 
tamarack (Larix laricina) spur 2 was in a tall shrub zone (Betula glandulosa),  
spur 3 was in a low shrub zone just before the hut and spur 4 was just beyond 
the hut in a mixed low shrub/sedge zone.  Collar designations were as follows:

TF1hk = tower fen, spur 1, hummock
TF2hk = tower fen, spur 2, hummock
TF2hw = tower fen, spur 2, hollow
TF3hk = tower fen, spur 3, hummock
TF3hw = tower fen, spur 3, hollow
TF4hw = tower fen, spur 4, hollow

ZF collars were located in a sedge-dominated (Carex spp.) fen area of the 
peatland complex, north of the fen tower, and accessed from Route 391.  Three 
spurs were located perpendicular to the main boardwalk.  Spur 1 was on a treed 
ridge; spur 2 was in a shrub-dominated hummock-hollow area; and spur 3 was in a 
wet, sedge-dominated area near the edge of a palsa.  Collar designations were as 
follows:

ZF1hk = Zoltai fen, spur 1, hummock
ZF2hk = Zoltai fen, spur 2, hummock
ZF2hw = Zoltai fen, spur 2, hollow
ZF3b_moss = Zoltai fen, spur 3, brown moss
ZF3hw = zoltai fen, spur 3, hollow (Sphagnum)
ZF3hk = Zoltai fen, spur 3, hummock (Sphagnum)

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

Measurements were taken at collar sites that spanned the full range of 
hydrologic, plant community, and water chemistry gradients found in the larger 
peatland complex.

7.1.4 Projection

Not applicable.

7.1.5 Grid Description

Not applicable.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

The first version of the data were collected during the summer of 1994 between 
26-May to 16-Sep.  Water table and temperature measurements were recorded 
continuously from approximately 04-May-96 to 23-October-96.

7.2.2 Temporal Coverage Map

Not applicable.

7.2.3 Temporal Resolution

The data were collected continuously at a frequency of 30 minutes.  The value 
represents the averaged data values for the previous 30 minutes.

7.3 Data Characteristics

Data characteristics are defined in the companion data definition file 
(tgb3wd.def).

7.4 Sample Data Record

Sample data format shown in the companion data definition file (tgb3wd.def).

8. Data Organization

8.1 Data Granularity

All of the Water Table and Peat Temperature Data are contained in one dataset.

8.2 Data Format(s)

The data files contain numerical and character fields of varying length 
separated by commas. The character fields are enclosed with single apostrophe 
marks. There are no spaces between the fields. Sample data records are shown in 
the companion data definition file (tgb3wd.def).

9. Data Manipulations

9.1 Formulae

None.

9.1.1 Derivation Techniques and Algorithms

Not applicable.

9.2 Data Processing Sequence

9.2.1 Processing Steps

Temperature and water table data from the CR10 and CR7 dataloggers were 
downloaded every 3-4 days and entered into spreadsheets back at the lab.

9.2.2 Processing Changes

Not applicable.

9.3 Calculations

If a 888 is present in the dataset, it represents a measurement that was taken, 
but discarded.  If a 999 is present, then no data were taken.

9.3.1 Special Corrections/Adjustments

Not applicable.

9.3.2 Calculated Variables

Not applicable.

9.4 Graphs and Plots

None given.

10. Errors

10.1 Sources of Error

Instrument error could be caused by wire disconnection or shorting, multiplexer 
or datalogger malfunction, or battery failure.

10.2 Quality Assessment

10.2.1 Data Validation by Source

All data were plotted to determine if there were any outlying data points that 
were obviously incorrect.

10.2.2 Confidence Level/Accuracy Judgment

The confidence level in the dataset is quite high, since no complicated 
calculations are required and the instrumentation has been used before on 
similar projects by the members of TGB-03 and TGB-04.  Accuracy of the 
electronically gathered data is also high when compared to manual measurements 
taken by field workers on a weekly basis.

10.2.3 Measurement Error for Parameters

Ground Temperatures:  Type T thermocouple rated at +/- 0.01 C maximum error.
Water and Surface Levels:  Maximum error of 1 mm. 

10.2.4 Additional Quality Assessments

None required.

10.2.5 Data Verification by Data Center

Data were examined for general consistency and clarity.

11. Notes

11.1 Limitations of the Data

None given.

11.2 Known Problems with the Data

None.

11.3 Usage Guidance

None required.

11.4 Other Relevant Information

None.

12. Application of the Data Set

The water table and peat temperature data can be used in connection with the 
chamber flux and tower flux data to determine the CO2 exchange between the 
atmosphere and the peatland soils. The remote sensing images, the chamber plant 
community data, and chamber NEE data, can be used to scale the CO2 fluxes from 
the plot scale to wetland landscape.

13. Future Modifications and Plans

These data are in draft format.

14. Software

14.1 Software Description

Not applicable.

14.2 Software Access

Not applicable.

15. Data Access

15.1 Contact Information

Ms. Beth Nelson
BOREAS Data Manager
NASA GSFC
Greenbelt, MD 
(301) 286-4005
(301) 286-0239 (fax)
Elizabeth.Nelson@gsfc.nasa.gov

15.2 Data Center Identification

See Section 15.1.

15.3 Procedures for Obtaining Data

Users may place requests by telephone, electronic mail, or fax.

15.4 Data Center Status/Plans

The TGB-01/TGB-03 water table data are available from the Earth Observing System 
Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) 
Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: 

ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov

16. Output Products and Availability

16.1  Tape Products

None.

16.2  Film Products

None.

16.3  Other Products

Comma-separated American Standard Code for Information Interchange (ASCII) files 
with text delimited by single quotes ().

17. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Campbell Scientific Corporation CR10 Manual.

Campbell Scientific Corporation AM416 Manual.

17.2 Journal Articles and Study Reports

Bubier, J.L., T.T. Moore,  L. Bellisario, N.T. Comer, P.M. Crill. 1995. 
Ecological Controls on Methane Emissions from a Northern Peatland Complex in the 
zone of discontinuous Permafrost, Manitoba, Canada.  Global Biogeochemical 
Cycles. Volume 9, Number 4, pp. 455-470.

Roulet, N., S. Hardill, N. Comer, N. 1991. Continuous Measurement of the Depth 
of Water Table (Inundation) in Wetlands with Fluctuation Surfaces.  Hydrological 
processes.  Volume 5, pp. 399-403. 

Sellers, P.and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment 
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). 

Sellers, P.and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment 
Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). 

Sellers, P.and F. Hall. 1997. BOREAS Overview Paper. JGR Special.

Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere 
Study: 1994 Operations. NASA BOREAS Report (OPSDOC 94). 

Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere 
Study: 1996 Operations. NASA BOREAS Report (OPSDOC 96). 

Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. 
Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. 
Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and 
early results from the 1994 field year. Bulletin of the American Meteorological 
Society. 76(9):1549-1577. 

17.3 Archive/DBMS Usage Documentation

None.

18. Glossary of Terms

None given.

19. List of Acronyms

    ASCII   - Amercan Standard Code for Information Interchange
    BOREAS  - BOReal Ecosystem-Atmosphere Study
    BORIS   - BOREAS Information System
    CB      - Collapse Bog
    CF      - Collapse Fen
    DAAC    - Distributed Active Archive Center
    EOS     - Earth Observing System
    EOSDIS  - EOS Data and Information System
    GSFC    - Goddard Space Flight Center
    NASA    - National Aeronautics and Space Administration
    NEE     - Net Ecosystem Exchange
    NSA     - Northern Study Area
    ORNL    - Oak Ridge National Laboratory
    PANP    - Prince Albert National Park
    SSA     - Southern Study Area
    TF      - Tower Fen
    TGB-03  - Trace Gas Biogeochemistry Team 3
    URL     - Uniform Resource Locator (a World Wide Web address)
    ZF      - Zoltai Fen

20. Document Information

20.1 Document Revision Date

Written:
Last updated:  05-Jun-98

20.2 Document Review Date(s)

BORIS Review:  12-Mar-98
Science Review:

20.3 Document

20.4 Citation

None given.

20.5 Document Curator

20.6 Document URL

Keywords
---------
Peat temperature
Water temperature
Bog Shoe

TGB01_TGB03_WaterTable.doc
06/11/98