Estimation of Soil Moisture Content Using GPR and Time- Lapse Resistivity: A Case Study of KNUST Anwomaso Oil Palm Plantation

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The viability of the ground penetrating radar (GPR) and time lapse resistivity measurements to assess the temporal and spatial variation of the volumetric water content in soil was tested in this work at the KNUST Agricultural Research station at Anwomaso - Kumasi. In the case of the GPR, the surface water content was measured with the ground wave, which is a direct wave between the transmitter and receiver through the upper centimeters of the soil. Spatial water content variation was measured on a 32 day monitoring period along four (4) 82 m profile lines. Electrical resistivity tomography (ERT) was used to measure resistivity at the experimental site with the objective of quantifying soil moisture for 20 days. This was based on the fact that, the degree of water saturation affects the resistivity measured hence water moisture could be imaged from the resistivity measurements. The time-series data set was used to generate desaturation models. It was observed from the results that rainfall affects the volumetric soil water and the resistivities measured. It was concluded that the non-invasive GPR measurements provide the means to accurately and consistently monitor the spatial water content variation in time at shallow depths with water content ranging from 0.06 m3/m3 to 0.4 m3/m3 whereas resistivity measurements are useful in imaging the moisture content at deeper depth.
A Thesis Submitted to the Department of Physics,Kwame Nkrumah University of Science and Technology,in partial fulfillment of the requirements for the degree of Master of Philosophy (Geophysics)