Soil Water Characteristic Curve ( ) K ( ) ae SWCC for Different Soils These curves depict drying soil. Wetting and Drying Soil In general, It is harder to drain pores than fill them. Small pores tend to fill first but drain last. Large pores tend to drain first but fill last. If a pore is isolated, it might not fill or drain at the same time as other pores of its size. The tension head ( ) changes more quickly when small pores are filling or draining. The changes more quickly when the large pores are filling or draining. Wetting vs. Drying Drying: ( ) decreases slowly and quickly as large pores begin draining. Wetting: increases slowly and ( ) quickly as small pores fill first. For any soil, wetting curves have a steeper slope until large pores fill. Example: <a href="/keyword/sandy-loam/" >sandy loam</a> soil Tension Head ( ) cm Dr yin g g tin et W K( ) vs. <a href="/keyword/sandy-loam/" >sandy loam</a> Clay nd Sa Clay Note: crossover point where clay K &gt; sandy K. At low , clay K is higher!! At crossover, the large pores in SL are mostly filled with air. BUT A lot of the small pores in the clay still have water in them. ay Cl nd Sa yL oam yL oam 0.5 0.25 0.05 0.0 Vol. Water Content (cm3/cm3) K( ) vs. At high water contents, coarse soils have a higher hydraulic conductivity than fine soils. At low water contents, fine...