Wetting Patterns in a Subsurface Irrigation System Using Reservoirs of Different Permeabilities: Experimental and HYDRUS-2D/3D Modeling

Abstract

Precipitation in arid lands is low and often highly variable; therefore, efficient irrigation is the best approach for managing limited water supplies and irregular precipitation events for establishing seedlings. The HYDRUS-2D/3D software is a useful tool for simulating water content distribution in the design of subsurface irrigation systems, determining the proper locations of reservoir and plant, irrigation scheduling and maximizing water use efficiency. In this study, wetting patterns around the reservoirs with different permeabilities (low, medium, and high) were assessed in the field and simulated using the HYDRUS-2D/3D software. Different amounts of animal manure and wheat straw were mixed with clay fractions to produce the reservoirs with different permeabilities. The results showed that the highest soil water content was observed near the reservoir, and it decreased with distancing from the reservoir. In the high permeability treatment (with saturated hydraulic conductivity, Ks = 0.2 cm/day), a large volume of water was released for almost three days, so that more water was deep-percolated and lowered the soil water available to plant roots. In the low and medium permeability treatments (Ks = 0.08, and 0.06 cm/day, respectively), the water slowly leaked, and the maximum soil water content was observed in the 20–40 cm layer over time. The HYDRUS-2D/3D software was able to simulate water flow and soil water content during the growth period of plants, with a high correspondence between measured and simulated soil water contents (R2 = 0.90–0.95), which was higher in the lower discharges.