PVC Well B1 at Na Pohaku o Hauwahine

The PVC mat penetration device, Well B1, is located at Station B1 just outside the open water ponds restoration site at Na Pohaku o Hauwahine.

The following legend applies to the graph above:
Vertical lines "I" and "II" mark changes in the water level measurement device: before I - two measurements of water or slurry thickness made at this station in April and June during augering and penetration device installation; I - first measuring tape device used (3 measurements); II - final tape device (see photo at right) with modified weight used. Fine dashed line is the water level recorded at the Na Pohaku wetland ponds, surveyed to the same base elevation. Heavy blue line is the measured height of water above "solid" bottom. The heavy green line represents "top of mat" calculated as tape reading from solid bottom to pipe lip minus pipe extension above mat with a correction factor to account for mat depression resulting when standing beside the well. The heavy brown line represents "bottom of mat" calculated as "top of mat" minus mat thickness. Vertical line representing the PVC casing is shown at a selected point in time, plotted from the measurement from solid bottom to pipe lip. The casing is attached (and moves with) the marsh "surface" (green line).
Sta. GPS:
Date installed:
Pipe length:
Ext.above mat:
Mat thickness:
Under mat:
June 2002
3.15 ft.
0.90 ft.
1.35 ft.
water
DISCUSSION Well B1 is located close to the wetland ponds restoration site at Na Pohaku o Hauwahine and water level measurements are made frequently, partly to provide assessment of variability in the measuring process itself. Consequently, this graph of water level may be less smooth that that generated for wells monitored less frequently. There is reasonably good agreement between the water level measured in Well B1 and water level in the pond (fine dashed line) located about 10 m away, after event "I."

Well B1 describes the "Floating Mat" Model of the marsh surface. The vegetation mat is clearly floating on a layer of water. This layer is typically 30 to 36 inches thick in this area, and about half or a little less of the water thickness saturates the vegetation mat itself; that is, the 15 to 16 inch thick mat is mostly below the water surface. The surface of the mat, however, remains a constant distance above the water surface, indicating that this organic layer or peat is floating unconstrained on the water. Note also that changes in water level in the well are not exaggerated relative to changes in water level in the nearby open pond, another indication that water level measurements are being made here in a covered body of surface water and not in an aquifer.

The 2002 dry season change in water level represented by measurements made between July 31 and October 14, 2002 averaged -0.008 ft/day (-2.6 mm/day). This dry season decline closely matches that of the ponds water level (-0.009 ft/day or -2.8 mm/day) between the same dates.

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