Soil Water Content Distributions between Two Emitters of a Subsurface Drip Irrigation System

Subsurface drip irrigation (SDI) systems are increasingly being used in agriculture in attempts to use the available water more efficiently. The proper design and management of SDI systems requires knowledge of precise distribution of water around emitters. We conducted both field and numerical experiments to evaluate the soil water content distributions between two neighboring emitters when their wetting patterns started to overlap. The experiments involved SDI systems with emitters installed at different depths and with different spacings along the drip lateral. The HYDRUS software package was used to analyze the field data, assuming modeling approaches in which emitters were represented as (i) a point source in an axisymmetrical two-dimensional domain, (ii) a line source in a planar two-dimensional domain, or (iii) a point source in a fully three-dimensional domain. Results indicated that SDI systems can be accurately described using an axisymmetrical two-dimensional model only before wetting patterns start to overlap, and a planar two-dimensional model only after full merging of the wetting fronts from neighboring emitters. A fully three-dimensional model appears to be required for describing subsurface drip irrigation processes in their entirety.