Measurements of water table height in the Shad Creek marsh, Rowley, MA, located near the Shad Creek eddy flux tower. Measurements were taken every 5 minutes at each logger along a transect of water level loggers running perpendicular to the Shad creek stream bank, MAR-RO-Wtable-Shad for April-November 2018.
A transect of wells is established on the marsh platform, perpendicular to the marsh edge. A total of 4 wells are dug to the depth of the water table under the marsh platform. Wells S101 to S104 are spaced approximately evenly within the first 2m of marsh edge . A water level logger, referred to as the tide gauge, (Onset HOBO U20 series) is placed in the creek near the bottom slightly offset from the transect (~8m East and 0.5m from the creek edge). This offset is needed to protect the logger from boat traffic. Individual water level loggers (Onset HOBO U20 series) are used in each well and they measure water height in terms of absolute pressure. Barometric pressure is measured above ground with an additional Onset HOBO U20 series water level logger to tease out the atmospheric pressure from water column pressure. Prior to deployment, each water level logger is sealed in protective plastic whirl-pak bags filled with freshwater, and calibrated to known water depths. Once in the field, water height measurements, in terms of absolute pressure, are recorded every 5 minutes. Pressure readings are uploaded from the HOBO water level loggers using HOBOware software which compensates for temperature, fluid density, and barometric pressure, then are converted to absolute water height above the river bottom. Data is QA/QC'd to ensure that the loggers report the same flood water elevation on the marsh surface. The surface elevation of the marsh as measured by the marsh water level loggers must match that of the gps'd surface elevation. Any corrections made to a particular logger data field (logger # Dc (m)) are reported in the Offset corr field (Offset corr logger # (m)). Shad Creek is completely dry at low tide.
Well Location Information:
Logger Well Height of Marsh Surface Above Creek Bottom (m) Horizontal Distance Upland of Creek Edge (m)
tide gauge Nref 0 0.23
1 S101 1.109 0.00
2 S102 1.125 0.20
3 S103 1.095 0.56
4 S104 1.049 1.01
Logger 7 tide gauge located near river bottom.
Marsh wells S101, S102, S103 and S104 move from water edge into the marsh platform.
NOTES AND COMMENTS:
Due to occasional equipment malfunction, readings are not continuous throughout the field season. Times in EST.
The Shad ref logger fell from the holder during the Aug-Sept sampling period. Data from that deployment is not corrected back to the water depth of the creek. All 4 loggers have been corrected to each other with the water flowing over the marsh but not to the creek depth. Use data from this sampling with caution.