Simulation of water flow in the soil under sub-surface trickle irrigation with water uptake by roots

Water uptake by roots is presented as a continuous sink function and introduced into the flow equation in the unsaturated zone. The steady-state non-linear equation is linearized and then solved numerically. The results show the influence of water demand, and of the intensity of the water source, on uptake by roots, on leakage under the root zone, and on the progress of the wetting front. The unique feature of this procedure is that it leads to a relatively simple differential equation which is essentially a corrected form of the solutions that disregard the uptake effect and the pressure head at the outlet of the sub-surface emitter. Although further confirmation is needed before the results can be applied for engineering purposes, the general behaviour and flow characteristics in the soil are satisfactorily simulated, and are also validated by the field experiments.