Application of a water infiltration model for simulating water
repellency of humus soil
Abstract
Taking hydrophilic and water-repellent soils from the Guishui River
Basin as the research object, one-dimensional infiltration experiments
were conducted to study the effects of soil water repellency on
cumulative infiltration (CI) and the infiltration rate (IR). The test
results show that, for the hydrophilic soil (HS) sample, the CI
increases monotonously with time and the IR decreases monotonously. For
the water-repellent soil (W-RS), however, the following characteristics
were observed: (1) There is an inflection point in the CI and a sudden
increase in IR. Larger values of the initial soil water content produce
an earlier and more significant inflection point in CI, and a larger
peak value of IR. (2) The post-peak stable IR is greater than that the
pre-peak value, ignoring the beginning of rapid infiltration, and the
overall IR presents a single peak. The applicability of various water
infiltration models was analyzed for the two soil types. Numerical
analysis suggests the following conclusions: (1) For both HS and W-RS,
the Kostiakov function, Gamma function, and Beta function (BF) models
exhibit good applicability. (2) For W-RS, the Gauss function model not
only reflects the monotonous decrease in IR, but also produces a steady
IR in the initial stage, a gradual increase before the peak value, and a
gradual decrease after the peak value. Similarly, the BF model reflects
the monotonous decrease in IR. A piecewise BF can also reflect the
U-shaped change in rapid infiltration before the inflection point, as
well as the gradual increase and right-skewed distribution curve of W-RS
infiltration before and after the inflection point. The BF model
achieves the best simulation accuracy and has the widest applicability.