1. Infiltration

2. Infiltration definitions
Infiltration rate: the volume of water flowing into the soil profile per unit of surface area per unit time
Infiltrability: the infiltration rate resulting when water at atmospheric pressure is made freely available at the soil surface
Supply controlled: when the rate of water delivery to the surface is less than the infiltrability
Soil controlled: when the rate of water delivery to the surface is greater than the infiltrability

3. Ponded infiltration

6. (deep sandy loam)

7. Green-Ampt model (1911)
a simplistic but elegant approximation of the ponded infiltration process
works best when:
wetting front is sharp
soil is coarse-textured
soil is initially dry
soil texture is homogeneous in the wetted region
air-entrapment and crusting are not significant

9. Set the ponded infiltration rate equal to the rainfall intensity.
Calculate the cumulative ponded infiltration for that rate.
Assume that “the maximum possible infiltration rate at time t (t > 0) is determined uniquely by the value of the cumulative infiltration in the interval up to time t.” (Mls, 1980)
Calculate time required for rainfall to supply the calculated cumulative infiltration.
Kutílek, M Constant-rainfall infiltration. Journal of Hydrology 45:

10. Green-Ampt-Kutílek
To estimate time of ponding (tp) for rainfall at a constant rate (r)
Let H0 = 0, solve for Lf

11. Example calculation Rainfall at 1.5 cm h-1 Silt loam soil
K = 0.65 cm h-1;
e = 0.49 m3 m-3
i = 0.15 m3 m-3
Hf = -17 cm of water
Estimate the time to ponding

12. Preferential flow
water flow through distinct pathways that constitute only a fraction of the soil's total volume
promoted by
fine over coarse layering
hydrophobicity
air entrapment
clay or sand lenses
macropores formed by:
animals, roots, shrink-swell cracks, etc…