Special Boundary Conditions In HYDRUS (2D/3D) for Irrigation Systems.

We have implemented into HYDRUS (2D/3D) several specialized boundary conditions that allow modeling of various system-dependent irrigation systems. These include a) a dynamic evaluation of the wetted area for surface drip irrigation (evaluates the spatial distribution of the discharge rate at the soil surface as a function of time), b) a subsurface drip characteristic function to account for back pressures (evaluates the source discharge while considering emitter properties, inlet pressure, and effects of the soil hydraulic properties), c) system-triggered irrigation, among other features. Irrigation can be triggered by the program when the pressure head at a particular observation node drops below a specified value. Irrigation is then initiated at a specified rate and duration, after a specified lag time, at a selected boundary. These, and other, system-dependent boundary conditions have been implemented into version 2 of the Professional Level of HYDRUS (2D/3D). Many other new features and options [e.g., support for complex general three-dimensional geometries; properties specified on geo-objects rather than a FE Mesh; import of properties and geometries from various formats; new wetlands, fumigant, and Unsatchem modules; compensated root water and nutrient (passive and active) uptake, and many others] have been implemented also.