Date of Award:

5-2015

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Scott B. Jones

Committee

Scott B. Jones

Committee

Lawrence E. Hipps

Committee

Grant E. Cardon

Abstract

Increase in world population rate has augmented the global water use in municipal, industrial, and agricultural sectors, with renewable water resources changing
very little with time. Climate change and variability, degradation of water quality as a result of industrial waste streams, animal manure and waste, application of chemicals, pesticides, pharmaceuticals, heavy metals, etc. have largely influenced the quantity and quality of soil water. Root zone water helps sustain the agricultural industry by providing much of the water needed for irrigation. It is critical to monitor the soil water availability, especially within the plant root zones. The subsurface water tends to flow to the surface in response to environmental interactions such as hot and dry climate, bare surface exposed to sunlight and wind, and soil characteristics, resulting in a significant evaporative loss or depletion from the water balance. While numerous measurement techniques are available to track moisture loss in soil, none of these methods are capable of tracking soil moisture loss instantaneously on a point scale. The aim of this research project was: 1) to estimate subsurface evaporation rates using a heat pulse probe (HPP) array that measures temperature and determines soil thermal properties in a vertical soil profile on a millimeter depth scale; and 2) to develop a fully automated microlysimeter (FAML), to track moisture losses in situ from the difference in mass changes recorded by a load cell. In the second chapter of this thesis, near real-time estimates of subsurface evaporation rates were obtained from the on-sensor calculation of soil thermal properties using temperature rise data. The work performed gave an assessment of fine scale determination of subsurface evaporation rate along with the advantages and limitations of the applied HPP design. In the third chapter, the utility of the FAML design was assessed in long-term monitoring of soil evaporation for extended depth in the soil profile. The FAML measurement results were inconsistent with the manual measurements. This led us to perform HYDRUS-1 D numerical simulations. Overall, using proper correction methods, both of these tools have the potential to improve in situ, real-time, and long-term evaporation measurements.

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