Field Testing of a Two-dimensional Soil Moisture Model Simulating Water Table Fluctuations1
- Michael J. Fayer and
- Daniel Hillel2
An attempt has been made to test the validity of a two-dimensional model of soil-water dynamics in a sloping field, with respect to groundwater level fluctuations during several infiltration-drainage cycles. The data from rain recorders, runoff plots, water table wells, tensiometers, and an evaporation pan were used to describe the various initial and boundary conditions. Soil hydraulic properties were determined from undisturbed cores and in situ methods. Comparisons of the predicted and measured water table positions were used to judge the model's capabilities. After two one-week periods of no rainfall, during which the actual water table fell 11 and 79 cm, the predicted water table levels were within 1.5 and 8 cm, respectively, of the measured levels. Before and immediately after periods of rainfall, the predicted water table levels were usually within 2 cm of the measured levels. As the water table rose in response to the rainstorm, however, the predicted rise was only one-half that measured in the field. Altering the shape of the moisture characteristic programmed in the model nearly doubled the predicted rise. Hence the discrepancy between prediction and observation may be due to insufficient accuracy in determination of the soil moisture characteristic in the very wet range, or to failure to account for air occlusion or hysteresis.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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