Abstract:Soil
cracks significantly affect preferential flow; however, there are some
uncertainties associated with the effect of soil cracks on preferential
flow in karst areas in southwest China. In this study,
ground-penetrating radar (GPR) was
applied to pedons to investigate the soil crack properties (inclusion,
width, and configuration). Blue dye tracing experiments were designed,
based on geophysical detection results, to assess the influences of
inclusions (sand grains and rock fragments), crack width (1, 1.5, and 2
cm), and configuration (I-shape, V-shape, and Λ-shape) on the
preferential flow. Our results indicated that (1) GPR envelope can
describe the configuration of isolated soil cracks; (2) the Brilliant
Blue FCF (C.I. Food Blue 2) infiltration rate and depth were over 1.5
times slower and 1.2–3.8 times lower those of water, respectively,
during infiltration; (3) soil cracks can accelerate infiltration and
increase the maximum dye-penetration depth, cumulative infiltration, and
wetting front depth by at least an average of 5.2% and 63.2%,
respectively; and (4) the I- and Λ-shaped soil crack configurations
contributed to preferential flow, while the flow was not observed along
the V-shaped configuration crack pore paths. The I-shaped
configurations, with a width of 1.5 cm, were filled with rock fragments
and had higher preferential flow ratios (18.2%–52.3%) and length
indexes (4.0%–33.8%) than those of other configurations. Inclusions,
crack widths, and configurations had significant influences on
preferential flow (p < 0.05).
The
influence of soil crack properties on preferential flow cannot be
neglected during vegetation restoration and groundwater security
processes in karst areas.
KEYWORDS:crack, configuration, preferential flow, karst, ground-penetrating
radar, Brilliant Blue FCF