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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Agricultural and Biosystems Engineering

First Advisor

Todd P. Trooien


A water balance model was successfully modified to determine yield response to tile drainage in waterways based on climate data. Modifications to the model were completed based on field measurements. Infiltration and tile drainage routines in the model were modified to improve the model simulation of the water table. Additionally the tile drainage simulation was modified to include a variable hydraulic gradient and a macropore flow component.
The water balance model was run for 17 years of climatic data (1986-1989, 1992-2000, and 2002-2005) collected at Brookings, South Dakota. The simulations were run for two conditions, one condition containing artificial subsurface drainage (drained condition) and one condition containing natural subsurface drainage (undrained condition).
Average relative yield for the drained condition was 55.6% of the yield potential if the com crop received no water stress. The drained condition relative yield had a standard deviation of 18% for the 17 years of simulation. The average relative yield for the undrained condition was 53.9% with a standard deviation of 15.6% for the 17 years of simulations. These simulations showed an average advantage for the drained condition of 1.7% improvement in yield.
Field measurements were taken of the hydraulic gradient throughout the 2005 growing season. The hydraulic gradient varied between 0.046 and 0.026 m/m (0.046 and 0.026 ft/ft). The hydraulic gradient measurements were used to develop a routine in the model to estimate the hydraulic gradient based on the water table elevation.

Library of Congress Subject Headings

corn yields
South Dakota
computer simulation
computer simulation
mathematical models


Includes bibliographical references (54-57)



Number of Pages



South Dakota State University


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