Assessment of the preferential flow characteristics and flow types on a
slope in a small headwater catchment
Abstract
Preferential flow plays an important role in soil water retention,
movement, and solute transport. Heterogeneity, uncertainty, and the
scale of preferential flow are the focus of the current research. The
multi-index method and preferential flow classification method were used
to identify and quantify preferential characteristics and flow types at
three points on a slope in the upstream portion of a drinking water
supply area. Results show that the infiltration depth of the
preferential flow on the hillslope is about 400 mm. The preferential
flow fraction of the stain profile ranges from 56.6 to 74.8%. The
result of multi-index evaluation indicates that the weight of the peak
value of the stained area and coefficient of variation are the two
indexes that have a greater influence on the preferential flow.
Regarding the difference in preferential flow at different slope
positions, the peak value of the stained area at mid-slope is higher and
the coefficient of variation is lower, indicating that the preferential
flow at mid-slope is more developed than upslope and downslope. The
results of the quantitative analysis of preferential flow types indicate
that the dyeing depth can be divided into three parts with dividing
points at 100 and 275 mm due to the distribution of the stain width. The
main flow type is macropore flow, especially macropore flow with mixed
interaction, accounting for 49.8, 52.2, and 61.3% of the flow types at
upslope, mid-slope, and downslope locations, respectively. The
interaction between macropores gradually decreases with increasing soil
depth and increasing elevation. As for the factors influencing
preferential flow type, correlation analysis found that the higher the
soil moisture content, the stronger the interaction between macropores.
Influenced by bulk density, saturated conductivity, and porosity, matrix
flow in the soil is relatively stable with a depth of approximately 10
cm. The study results can provide a reference for subsequent research on
the preferential infiltration mechanism at different slope positions and
the transport characteristics of water and nutrients.