WATER DROP ENERGY AND SOIL SEAL PROPERTIES

Rain properties (depth, drop size, and impact velocity) affect the inf iltration 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 o f this study was: to find a unique function of rain properties that de termines 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 hei ghts of 0.4, 1.0, 2.0, 6.0, and 10.0 m on two soil samples: Ruppin ham ra (sandy loam, mixed, Typic Rhodoxeralf), and Ruhama loess (silty loa m, mixed, Calcic Haploxeralf). The FIR of the two soils decreased with increasing kinetic energy (RE) of the drops. The sandy loam was less stable than the silty loam, and seal formation in it was more suscepti ble to the RE of the drops. The infiltration decay process was better correlated with rain momentum than with rain depth or KE. Thus, predic tion of infiltration rate decay for a given soil exposed to rains of v arious drop sizes and velocities is best based on drop momentum and th e soil stability constant.