Modelling of field drainage using the numerical method of lines.

摘要

Simulation of soil water flow under transient unsaturated conditions is based on Richards' equation. A one-dimensional unsteady state numerical model (NONSAT) was developed, and it incorporated water uptake by plants. The numerical method of lines (NML) was used to solve Richards' equation. The model accuracy was tested by comparing numerical solutions with those of the HYDRUS model which is based on finite elements, and with field experimental data (pressure head, water content, drainage volume) collected in three undisturbed pan lysimeters cultivated under a potato field at Saint-Pierre de l'ile d'Orleans, near Quebec, Canada over a period of 195 days. Agreement between measured and simulated values was better for NONSAT than for HYDRUS. For thethree pan lysimeters, NONSAT showed an average under-estimation of pressure head of about 2.5 cm. For NONSAT, the difference between measured and observed water contents ranged from 0.009 to 0.123 whereas observed and simulated drainage amounts varied,on average, by 0.3 cm, which corresponds to 15% of the average weekly drainage. The daily mass balance error of NONSAT did not exceed 0.01%, however that for HYDRUS varied between -0.01 and -0.11%.