Award Date

August 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Michael Nicholl

Second Committee Member

David Kreamer

Third Committee Member

Michael Moran

Fourth Committee Member

Dennis Bazylinski

Number of Pages

156

Abstract

Prediction of water movement in the vadose zone requires knowledge of either the unsaturated hydraulic conductivity, K(θ), or the hydraulic diffusivity, D(θ), of the soil as a function of the moisture content. However, both K(θ) and D(θ) are difficult to obtain for moderately dry soils because the tests are time consuming and expensive. In order to address this issue, Globus and Gee (1995) developed a “heat pipe” method that allowed for the direct estimation of D(θ) and K(θ) for moderately dry soils on relatively short time scales. They proposed that exposing a sealed horizontal soil column to a steady thermal gradient would induce a redistribution of soil moisture that would eventually reach steady-state. Subsequent measurements of moisture content along the column could then be combined with independently obtained moisture retention data to estimate D(θ) and K(θ). The purpose of this research is to evaluate whether Globus and Gee’s “heat pipe” is a viable method for estimating the unsaturated hydraulic conductivity. Specifically, the goal was to determine if an improved experimental design will lead to steady-state conditions.

Eleven experiments were performed inside a 10-cm long horizontal soil column (2.63 cm diameter). The first four experiments were conducted at a gravimetric initial moisture content of 0.12, and showed little evidence of thermally driven moisture redistribution. The lack of redistribution can be attributed to zones of high moisture content that likely created barriers to vapor flow due to a lack of well-connected open pores. The last seven experiments were conducted at an initial moisture content of 0.05. In contrast to the first four experiments, moisture redistribution was observed in each of the seven trials, suggesting vapor flow will occur if there are sufficient continuous, open, well- connected vapor transport pathways. All experiments had evidence of moisture traveling between the test column and the external environment, which inherently suggests that the system is unlikely to reach steady-state conditions using the proposed experimental design.

Keywords

Unsaturated hydraulic conductivity; Vadose zone hydrology

Disciplines

Hydrology | Soil Science

Language

English


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