Water drop energy and soil seal properties

Rain properties (depth, drop size, and impact velocity) affect the infiltration rate (IR) curve and final IR (FIR) of soils. Because the IR is not a unique function of rain depth or rain energy, the objective of this study was to find a unique function of rain properties that determines the IR of the soil. Simulated rain of constant intensity (40 mm h⁻¹), with 2.53− and 3.37-mm-diameter drops, was applied from heights of 0.4, 1.0, 2.0, 6.0, and 10.0 m on two soil samples: Ruppin hamra (sandy loam, mixed, Typic Rhodoxeralf), and Ruhama loess (silty loam, mixed, Calcic Haploxeralf). The FIR of the two soils decreased with increasing kinetic energy (KE) of the drops. The sandy loam was less stable than the silty loam, and seal formation in it was more susceptible to the KE of the drops. The infiltration decay process was better correlated with rain momentum than with rain depth or KE. Thus, prediction of infiltration rate decay for a given soil exposed to rains of various drop sizes and velocities is best based on drop momentum and the soil stability constant.