Some moisture characteristics of a small column of sand
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Date
1996
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Publisher
University of New Brunswick
Abstract
Interest in soil-water relationships in the unsaturated zone has increased in the last
decade because of the concern that contaminants may have moved into the soil and the
water in that zone. Characterization of the soil-water relationships in the unsaturated zone
is complicated by hysteresis and the variation of soil moisture with depth. When
modelling the movement and storage of water in the unsaturated zone, it is necessary to
evaluate various parameters including: matric potential, soil moisture content, and most
importantly unsaturated hydraulic conductivity. Soil moisture retention curves developed
from soil moisture and matric potential data aid in the evaluation of unsaturated hydraulic
conductivity. The Brooks-Corey and the van Genuchten models are often employed to
estimate the unsaturated hydraulic conductivity as a function of volumetric soil moisture
content.
This report documents a series of experiments performed as part of a senior report
project. To demonstrate the variation of soil moisture content with depth, several short
stacked columns of sand were permitted to drain under the influence of gravity. An
outflow method was employed to measure the soil matric potential and soil moisture of a
sample of loose sand. Data collected from the outflow experiments was used to
numerically estimate the relative unsaturated hydraulic conductivity as a function of
moisture content. The van Genuchten model and the Brooks-Corey model were both
used to calculate the relative unsaturated hydraulic conductivity.
These experiments have demonstrated the complexity of processes associated with soil-water relationships in the unsaturated zone. However, the basic principles of the soil-moisture relationships for a sample of sand were characterized.