3.3 Influence Range of Water Infiltration in Bioretention
Facilities
A water content map of the loess site was drawn based on data gathered
at different positions at different time points during the water
infiltration process (Fig. 8).
[Insert Figure 8]
In Bioretention I, 4 h into the process of infiltration, the vertical
diffusion velocity of water in the site was greater than that in the
horizontal direction. The shape of the soil infiltration range was
slender and pear-like. With an increase of infiltration time, the
horizontal diffusion of the soil accelerated and the vertical diffusion
decelerated until finally becoming stable. In Bioretention II, the
infiltration range in the initial stage has a round, flat pear shape.
The pear shape was gradually elongated as the infiltration progressed
because the vertical diffusion significantly increased over the
horizontal diffusion before becoming progressively stable.
In the initial stage of infiltration, water moving through Bioretention
I significantly influenced the site’s water content. After about 4 h of
infiltration, the influence range was smaller in Bioretention II than in
Bioretention I. The wetting front was located at the position where the
water content increased by 3%, so in Bioretention I, the wetting front
diffused to 1.5 m away from the centerline of the facility in the
horizontal direction at a depth more than 2.54 m. In Bioretention II,
the diffusion range was 2 m in the vertical direction and 1.5 m in the
radial direction. The water infiltration range increased over time and
was more intense in Bioretention II than elsewhere in the site. When the
infiltration time reached 24 h, the horizontal infiltration effect was 3
m within Bioretention II, which was 1.75 m greater than that in
Bioretention I.