Linkflow, a Water-Flow Computer-Model for Water-Table Management .1. Model Development

Abstract

A computer simulation model, LINKFLOW, was developed to calculate the movement of water during various water table management practices, namely subsurface drainage, controlled drainage, and subirrigation. The model can simulate water movement through a heterogeneous and anisotropic saturated soil and includes an unsaturated flow component with a zone of water extraction by plant roots. The computer program links a newly developed one-dimensional unsaturated water flow model to an existing but modified three-dimensional saturated water flow model, MODFLOW. The water movement is simulated for a region of the field, and results obtained define water conditions in the root zone for a wide range of soil, topography, drain location, and weather conditions. LINKFLOW is unique among soil waterflow models because of the following features: I) it can simulate soil-water conditions beneath a crop on land with varying topography; 2) it can determine 3-D flows from drains in a heterogeneous, anisotropic soil; and 3) it can simulate the effects of different automated control strategies for subirrigation. Results can be presented in tabular format, contour map format, and/or a 3-D surface format to help understanding flow behavior of the system. A subirrigation case simulation is presented to illustrate just one example of the model's use in water table management studies. This article focuses on the development of the simulation model.