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Fig. 4. Comparison of moisture content in the right and central coarse sand inclusions in Fig. 3 during drainage. "Height of WT" refers to height of the water in the reservoirs relative to the base of the tank. "Pressure Head" refers to the equivalent pressure head at the measurement point assuming hydrostatic conditions. Within the right sand inclusion, free movement of the air phase allows sequential desaturation at the four TDR locations. In the center sand inclusion, prevention of the invasion of the air phase (due to overlying fine sand) leads to delayed drainage of the upper TDR locations until air penetration of the overlying fine sand. (After Dunn and Silliman, 2003.)
