Air-entry pressure

25

5 cm

10 cm

e. Site 5--Intermittent pond.

f. Site 6--Mudflat.

h. Site 8--Mudflat.

g. Site 7--Mudflat.

Figure 24 (cont'd).

≥4.8 m (sites 410) (Fig. 25, Table 10).

closest to site 1 (sites 2 and 3) starting August 12

Air-entry pressure. Based on the moisture char-

and July 31, respectively. The remaining mudflat

acteristic curve for a sample collected from the

and intermittent ponded sites became unsaturat-

intermittent pond area (Fig. 28), the air-entry

ed at 5 cm deep in June but were rewetted by the

pressure was approximately 5 cbars for this fine-

flooding high tides of June 2325. Because of this

grained sediment. In the field a pressure of this

rewetting, most of these sites were saturated

magnitude can occur by a drop in water table

during the part of the summer when the poten-

such that the equivalent head pressure between

tial solar radiation is at its maximum. Unsaturat-

the surface of the sediment and the surface of the

ed conditions were detected again in July and

water table is 5 cbars. By expressing pressure in

persisted over the period monitored. Unsaturat-

units of "cm of water" (10.2 cm of water = 1 cbar),

ed conditions were detected later with increas-

we can estimate that a drop in the water table of

ing depth. Unsaturated conditions were detected

51 cm would result in air entry or desaturation of

down to 30 cm deep at sites with elevations of

21