Date of Graduation

Spring 2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

Committee Chairperson

Daria Nikitina, PhD

Committee Member

Martin Helmke, PhD, PG

Committee Member

Russell Losco, MA, PG, CPSS

Abstract

Tile drainage design influences groundwater flow pathways, residence time, and agrochemical transport in agricultural soils. This study evaluates how differences in drainage design affect subsurface flow behavior and contaminant transport in glacial till soils. A groundwater model was developed to compare conventional and controlled drainage systems with a shallow drainage system, and particle tracking was used to examine flow paths and residence times.

The results show that tile drainage creates distinct shallow and deeper flow pathways. In the conventional and controlled model, 88% of particles were captured by drains, while 12% reached the general head boundary. The shallow system drains captured 62% of particles, allowing more groundwater to move into deeper pathways. Most drain-captured particles reached the system within 5–8 days in the conventional and controlled system and 10–25 days in the shallow system, while deeper flow paths exceeded 100–250 days.

These differences affect contaminant transport. Nitrate reduction ranged from approximately 6.66% to near-complete along drainage pathways and increased to up to 88.5% along deeper pathways. Atrazine showed a similar pattern, with reductions ranging from 1.65% to 94.4% along drainage pathways. Incorporating sorption increased atrazine residence times, with a retardation factor of 4.05, indicating slower movement through the subsurface.

Overall, drain depth and spacing strongly influence groundwater flow and contaminant transport. Shallow flow pathways promote rapid transport with limited reduction, while deeper flow pathways increase residence time and allow greater interaction with the subsurface.

Final Version Confirmation

1

Download

Share

COinS