Degree Type

Dissertation

Date of Award

1988

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

Major

Water Resources

First Advisor

T. Al Austin

Abstract

A two-dimensional finite element model for soil-moisture flow in the saturated unsaturated zone was developed. The hydrologic parameters like precipitation, evapotranspiration, interception, surface runoff, and depression storage have been included in the model. The model considered layered soil formations. The Monte Carlo method was used to incorporate the stochastic nature of hydraulic conductivity into the flow model. The model can predict tile outflow and deep percolation given proper boundary conditions. Other output variables include pressure head, water content, and location of water table at various points in the two-dimensional soil profile. Outputs from the Monte Carlo simulation were used to predict the mean and standard deviation of those output variables;Saturated hydraulic conductivity values for each Monte Carlo run were generated from a log normal distribution with known mean and standard deviation of saturated hydraulic conductivity for each layer. Van Genuchten's model for the relative hydraulic conductivity was used. The Soil Conservation Service method of estimating surface runoff was used. Options are available for selecting models for estimating root water uptake;Six simulations were done for a period of 373.5 hours. The flow system consisted of a 182.9 cm (depth) by 1828.9 cm (width) soil profile divided into four layers with a tile at 121.9 cm depth from the surface. The simulations were made to determine the effect of input variables like mean and standard deviation of log saturated hydraulic conductivity, number of Monte Carlo runs, and ratio of horizontal to vertical saturated hydraulic conductivity;Based on the present study, it can be said the finite element method can be successfully used for two-dimensional saturated-unsaturated flow of soil moisture based on the continuity theory. The Monte Carlo method was shown to be satisfactory when applied to incorporate the stochastic nature of hydraulic conductivity in groundwater flow problems.

DOI

https://doi.org/10.31274/rtd-180813-3209

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Mushtaque Ahmed

Language

en

Proquest ID

AAI8909121

File Format

application/pdf

File Size

141 pages

Share

COinS