Peatland water table elevation is measured in a well near the peatland
center of each of six research watersheds and within the Bog Lake
Peatland. All of the peatwell sites have Belfort model FW-1 strip
chart recorders with a float and pulley system to monitor water levels
(data resolution 0.3 cm).
The peatlands are vegetated with plants ranging from Sphagnum to low
shrubs to mature black spruce (Picea mariana) and tamarack (Larix
laricina) trees. The organic soils (peat) in the interior of the
peatlands range from 1.8 m to 9.1 m in depth. Water tables are at or
near the peat surface. The peat is not stable for data recorders.
Therefore, shelters for the recorders are mounted on four 3.2 cm pipes
anchored through the peat into the mineral soil below. A 0.3 m section
of spiral auger was welded to the end of each pipe. A recorder sits on
a wooden platform that is about 0.6 m x 0.9 m in dimension and 0.9-1.2
m above the peat surface. Peat below the platform was excavated to a
depth of about 1.2 m. A stilling well (~0.3 m diameter galvanized
pipe) was originally placed into the hole and secured to the pipes.
The stilling wells have been replaced with wooden enclosures that
extend into the subsurface to prevent peat from collapsing into the
excavations. A float rises and falls in the stilling well with water
table fluctuations and rotates the recorder pulley via a flat metal
tape that is connected to a counterweight.
Peatland wells are visited weekly and recorder stripcharts are changed
at that time. Every several years, elevations are measured relative to
known benchmarks to determine the platform elevation in feet above
mean sea level. During the weekly visits, the depth to water from the
platform is determined with a tape measure and subtracted from the
platform elevation. This value is the elevation of the water surface
and is used to set the pen position on the chart. If the stripchart
reading differed from the check value, the chart values were adjusted
and notated on the charts. The starting and ending date/time and water
table elevation are recorded on each stripchart. Propane lamp heaters
were added to the shelters incrementally between 1990 and 2005 to
maintain an unfrozen pool for year-round operation. Before heating,
ice was chipped from nearby satellite wells when the recording
peatland wells were frozen and daily water levels were extrapolated
from water-table recession curves. If the recorder malfunctions for
some reason the missing values were estimated with consideration of
stream runoff and precipitation for the same time period, and from
water levels in the other peatlands.
The peatland water tables may quickly rise with rain or snowmelt
events, but fall (recess) at a slower rate. Daily high values were
read from the chart and entered into Microsoft Excel spreadsheets. All
data entries were verified and data plots were observed to detect any
suspicious values. The daily entries were then converted to metric
units and stored in a summary spreadsheet.
Peatland water level data collection has been uninterupted since 1961
at the S1, S2 and S3 sites. Data are uninterupted since 1962 at S4 and
S5. The S6 data are from 1965 to June 1974 and from April 1976 to the
present. Bog Lake data are uninterupted since July 1990. All water
table elevation data is presented in meters above sea level.
Study areas and methods are described in detail in the following
publication: Sebestyen, S.D., C. Dorrance, D.M. Olson, E.S. Verry,
R.K. Kolka, A.E. Elling, and R. Kyllander (2011). Chapter 2: Long-Term
Monitoring Sites and Trends at the Marcell Experimental Forest. In
Randall K. Kolka, Stephen D. Sebestyen, Elon S. Verry, and Kenneth N.
Brooks (Ed.). Peatland Biogeochemistry and Watershed Hydrology at the
Marcell Experimental Forest (pp 15-71). CRC Press, Boca Raton, FL.
https://www.fs.usda.gov/treesearch/pubs/37979.
