Abstract
Modern irrigation techniques use automated systems where irrigation schedules are controlled according to certain criteria. The objective of this study is to numerically estimate irrigation events, water content and temperature distributions, evaporation, drainage, and soil water under closed loop automated irrigation systems of a bare soil. The automated irrigation system is activated and deactivated according to the water content value. The governing equations for transient one-dimensional liquid water flow and heat transfer of unsaturated porous media are applied. The energy balance equation at the soil surface is used as an upper boundary condition based on measured meteorological data of Jeddah City. The results show that the current procedure can be applied to simulate different variables under automated irrigation systems. The water content shows periodic behavior, as well as time lags and decreases in amplitude with soil depth. The timing of applied irrigation has an important impact on evaporation and soil temperature. Applying irrigation water during the daytime leads to increased evaporation. The soil surface temperature decreases suddenly when water is supplied in the afternoon, while a slight increase is observed when irrigation is applied at midnight.