An electronic analog for unsaturated flow and accumulation of moisture in soils

Abstract

An electronic analog model of the unsaturated zone has been developed, based on the similarity between the integrated flow equation (5) and Ohm's law. The main difference between the two equations is compensated for by amplifiers. The model simulates one day in 2 s. There are ten normal layers, each with adjustable magnitude. Moreover, there is a top layer in which infiltration, ponding and runoff are simulated, and a drain layer with adjustable drain intensity. The normal layers contain an adjustable resistor for the connection with another layer and a function generator for the k( θ) relation. There are two transition layers which have to be placed at the boundary between two layers of different soil properties. Under saturated conditions the model is acting incorrectly, so that a too small thickness of the saturated layers is calculated. This can be compensated for by using an equivalent drain intensity which is lower than the real one. The model can be used to simulate the effect of natural rainfall and evaporation on moisture content at every depth. Soil physical properties and drainage conditions can be adjusted. Homogeneous as well as layered soil can be represented by the model. In particular, it can be applied to investigate the drainage requirements of soils. Some examples of the applicability of the model and short technical description are presented.