INVESTIGATING THE CRITICAL SHALLOW VADOSE ZONE: MODELING WATER FLOW CHARACTERISTICS AND NITRATE TRANSPORT WITH HYDRUS-1D USING TENSIOMETERS

Agricultural practices impact the Earth's critical zone by significantly contributing

to nitrate pollution. Understanding solute transport and water flow characteristics in the

critical shallow vadose zone is vital for hydrogeology, hydrology, environmental, and soil

sciences as it affects the water quality in the Earth's critical zone. While there have been

various studies on solute and water movement using tensiometers and HYDRUS-1D, no

project explicitly addresses water flow and solute transport in the critical shallow vadose

zone for a short-term water flux event. Utilizing tensiometers and HYDRUS-1D, this

project investigated relationships between the field data and modeling results to

determine the capabilities of HYDRUS-1D to capture transient properties of water flow

characteristics. We assessed water flow characteristics by evaluating relationships

between soil moisture conditions (water content), soil matric potential (pressure head),

infiltration rate, and porosity. We concluded that the water flow models successfully

transcribed the water flow characteristics observed in the field data. However, the solute

transport model was restricted to limited data, where environmental factors such as root

uptake, transpiration, or heat were not defined. Nonetheless, basic solute flow

characteristics were assessed through advection, dispersion, and diffusion mechanics. The

project's results contribute valuable information for agricultural management and offer

insight into differences between short-term and long-term water flux events.