Simulation of Soil Water Dynamics Under Surface Drip Irrigation from Equidistant Line Sources

One of the most important aspects of planning and management of a drip irrigation system is the determination of the soil moisture patterns formed under the emitter. In the present study soil water dynamics under surface drip irrigation from equidistant line sources are investigated using a simulation model, which combines hysteresis in the soil water characteristic curve, evaporation from the soil surface, and water extraction by roots. In this model a two-dimensional distribution of roots as well as a more rational way for the temporal distribution of the daily potential evapotranspiration are also incorporated. Soil water distribution patterns for two soil types (loamy sand, silt loam), two discharge rates (2 and 4 l m−1 h−1), two irrigation depths (30 and 40 mm), and two drip line sources spacing patterns (60 and 80 cm) are investigated. The numerical results showed that the soil water dynamics mainly depend on the soil hydraulic properties, the irrigation depth, and the drip line sources spacing. The results also showed that the irrigation efficiency and the actual evaporation decrease when the irrigation dose or the distance between the line sources increases. By contrast, the deep percolation increases when the irrigation dose or the distance between the line sources increases.