Simulation of Water Table Control Systems

Fine textured agricultural soils in humid regions are often too wet because they have slowly permeable layers at shallow depths. Sandy soils in humid regions can have reduced productivity from either being too wet or too dry because of extremes and irregularities of precipitation events over time, and they can be subjected to both of these soil-water extremes in the same crop season. To combat these problems, systems, which are capable of switching between irrigation and drainage modes several times within the crop season, are required. WTC systems, which meet this specification, are perfect under such conditions. Before installing a WTC system it is necessary to identify the optimum depth and spacing required for optimum crop growth and yield. This can be achieved through two main procedures: computer simulation, which enables a lot of design specifications to be tested in a relatively short time and with a low investment, and pilot projects which use real systems to study the behaviour of the system under different conditions. Both of the above outlined procedures were used in this research