A two-dimensional Richards equation solver based on CVODE for variably saturated soil water movement

A numerical model of two-dimensional soil water movement under surface drip irrigation condition was developed. The physical process of soil water movement is described by 2D Richards equation, and the upper boundary condition is depicted by the improved moving ponded area boundary. The partial differential equation (PDE) is transformed into ordinary differential equations (ODEs) through spatial semi-discretization and numerically solved by an ordinary differential equation solver (CVODE). The numerical and field experiments indicate the good performance of the model in terms of accuracy and efficiency. The model provides a useful tool for long-term simulation of soil water movement under surface drip irrigation. Also, the model can serve as a general 2D Richards equation solver for variably saturated soil water movement, which is named as TIVS model (Tsinghua Integrated Variably Saturated soil water movement model).