Assessment of the preferential flow characteristic 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 current research. The
multi-index method and preferential flow classification method were used
to identify and quantify preferential characteristic and flow types at
three points of a slope in the upstream of the drinking water supply
area. Results show that the infiltration depth of the preferential flow
on the hillside is about 400mm. The preferential flow fraction of the
staining profile ranges from 56.6 to 74.8%. The result of multi-index
evaluation shows that the weight of the peak value of the staining area
and coefficient of variation are the two indexes that have a greater
influence on the preferential flow. Regarding the difference of
preferential flow at different slope positions, the peak value of the
staining 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 at upslope and downslope. The results of the quantitative
analysis of preferential flow types show that the dyeing depth can be
divided into three parts with two dividing points at 100 and 275 mm due
to the distribution of stain width. The main type is macropore flow,
especially macropore flow with mixed interaction, accounting for 49.8,
52.2, and 61.3% 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 results can provide a reference for the
subsequent research on the preferential infiltration mechanism on
different slope positions and the transport characteristics of water and
nutrients.