Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Civil, Construction, and Environmental Engineering


Water Resources


Computer simulation was used to study the irrigation potential of corn on three selected soils in Iowa, representing sandy to heavy soils. The selected soils were Chelsea sand, Moody silt loam, and Albaton clay;A previously developed water balance model (Anderson, 1975) was modified, and used to simulate irrigation. The model was calibrated and applied to long-term weather data from the Doon, Burlington and Sioux City stations for Moody silt loam, Chelsea sand and Albaton clay, respectively, to define the probability of soil moisture shortage, and to determine the moisture stress index under natural conditions. Annual irrigation water needs and their frequency distribution, and the most efficient irrigation schedule for the three soils, were determined by incorporating a sprinkler irrigation subroutine into the model, which treated irrigation water as additional rainfall. Changes in surface runoff, deep percolation, water use efficiency, moisture stress and yield due to irrigation were calculated in the model by comparing the results of the runs under natural conditions with those under irrigation;The frequency distributions of length of stress period and annual irrigation water requirements were approximated by the Weibull distribution, and goodness-of-fit was justified by a chi-square test;Sensitivity of the model was analyzed with respect to the major soil properties including field capacity, wilting point, saturation moisture, and saturated hydraulic conductivity. Albaton clay and Chelsea sand showed the most and least sensitivity to changes in soil parameters, respectively.



Digital Repository @ Iowa State University,

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Zoreh Shahvar



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408 pages