Prediction of flow characteristics and risk assessment of deep percolation by ceramic emitters in loam

Emitter discharge is one of the most important parameters considered in the design, operation, and management of subsurface irrigation systems. The emitter discharge, if properly chosen, can eliminate surface runoff and minimize deep percolation water losses. The discharge from a ceramic emitter depends on the working pressure head and the ceramic hydraulic conductivity, so it is important to determine the optimal working levels for these two design parameters. In this work, it is confirmed that the HYDRUS-2D predictions of the cumulative infiltration and the horizontal wetting front are in good agreement with experimental results, and that the Hydrus-2D model can be used to accurately simulate soil water movement under subsurface irrigation with ceramic emitters. Additional simulations with HYDRUS-2D were used to study the effects of various design parameters (i.e. working pressure head and ceramic hydraulic conductivity) on emitter discharges in soils, deep percolation and soil wetting fronts. Results show that both the working pressure head and ceramic hydraulic conductivity have significant impact on the discharge of emitters in soil, and the deep percolation water losses. The emitter discharge in soil decreases with time and finally stabilizes. When the working pressure head and ceramic hydraulic conductivity are higher, the stable discharge (emitter discharge in soil at 120 h) is greater, and this situation may increase the risk of deep percolation. The relationship between the working pressure head, ceramic hydraulic conductivity, and stable discharge is developed as a power function. To satisfy the water requirements of trees with an active layer of root systems down to about 0-100 cm in the Loess Plateau in China and reduce the risk of deep percolation, it is recommended that the working pressure head should be 20-50 cm of water and the ceramic hydraulic conductivity should be between 0.1 and 1.9 cm h−1.