Well A3 in Kawai Nui Marsh

The PVC mat penetration device, Well A3A at Sta. A3, located just north of circle of papyrus east of the ponds restoration site at Na Pohaku o Hauwahine. The vegetation in this area is dominated by para grass and a large, circular patch of papyrus is located close by. Cattails are scattered about. Well A3 is hidden in the grasses just to the right of Well A3A.

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. Vertical line III marks the point that a second well (A3A) was installed approximately 3 ft. away (see Discussion, below). Blue line is height of water above the "solid" bottom; the thin blue line representing converted values from measurements made at Well 2. The green line represents "top of mat" calculated from tape reading from solid bottom to pipe lip. The dashed brown line represents the boundary between a darker, root zone, and deeper muck based upon a single measurement. It is assumed that this layer does not change in thickness, although this may not be a correct, still requiring further investigation.
Elevations are approximated to Mean Sea Level (MSL)

Sta. GPS:
Date installed:
Re-installed:
Pipe length:
Ext. above mat:
Mat thickness:
Under mat:
Clay layer at:
---
June 2002
Oct. 12, 2002
2.44 ft.
0.98 ft.
0.55 ft.
mud
+1.25 ft. (7)

DISCUSSION Station A3 is in an area generally similar to Station A2, but further out into the marsh. This is an area of the marsh possibly near the boundary between the "wet meadow" and floating mat. Presently, it is uncertain if water occurs between the vegetation mat and the underlaying sediment (pending aditional coring). Initially, this location showed a considerable "depth of water" (over 3 ft in Well A3). However, this seemed suspicious given other considerations. A second penetration, Well A3A, was installed nearby, revealing the bogus nature of the measurements being taken at Well A3. Apparently, the first well was accidentally installed over the geological bore hole. Measurements from Well A3 were recovered (transferred to represent the new well) by monitoring the water level in both wells for a period of time to establishing an average conversion value.

In this area, the marsh sediment consists of an upper organic or O horizon with conspicuous root development and a lower, clay horizon. The new well was established just before the rainfall of Oct. 15-17 which delivered over 2 in of rain at Na Pohaku o Hauwahine and effected a water level rise of 0.46 ft in the ponds. Measurements at Well A3A suggest that a rise in water level after rainfall input is not accompanied by a rise in the surface of the mat; in fact the elevation of the mat has remained very constant throughout the wet season. The water level, on the other hand, follows the marsh water level rather closely. The difference between drop-line measurements and the rod measurements is small, suggesting that between the bottom of the mat and the clay layer is a relatively thin muck material. However, as was the case with the initial Well A3, the drop-line penetration may be aided by the boring made to install the well pipe. Stability of the mat may be conferred by the large papyrus growth nearby. However, a short distance further out the vegetation mat lies on an extremely plastic layer (see Well A4), located even closer to the same papyrus stand.

The change in water level represented by measurements made between July 31 and October 12, 2002 (dry season WL decline) was -0.010 ft/day (-3.0 mm/day).

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