COMPUTER-SIMULATION MODEL FOR PREDICTING SOIL-WATER CONTENT PROFILES

A simulation model describing water movement through field-cropped soils was developed. The soil water flow equation, which included a root extraction term, was approximated using a finite difference technique. Hydraulic conductivity (K) and diffusivity (D) functions were calculated by using the Millinton-Quirk technique. The chosen boundry conditions, rainfall, evapotranspiration, and a fluctuating water table approximated those existing in the field. Submodels to calculate interception, evaporation, and transpiration were included in the model. Model predictions were in good agreement with field data from a fairly uniform soil. On a soil containing discontinous clay varves the predictions were not satisfactory when the original calculated K and D functions were used. Predicted and measured water content profiles were in closer agreement when the K and D functions were modified within the limits of the measured moisture retention curve data. © 1979 The Williams & Wilkins Co.