Numerical analysis of ponded infiltration experiment under different experimental conditions

Abstract

One of the most important properties, affecting the flow regime in the soil profile, is the topsoil saturated hydraulic conductivity (<I>K<SUB>s</SUB></I>). The laboratory-determined <I>K<SUB>s</SUB> </I>often fails to characterise properly the respective field value; the <I>K<SUB>s</SUB> </I>lab estimation requires labour intensive sampling and fixing procedures, difficult to follow in highly structured and stony soils. Thus, simple single- or double-ring ponded infiltration experiments are frequently performed in situ to obtain the field scale information required. In the present study, several important factors, affecting the infiltration rate during the infiltration experiments, are analysed using three-dimensional axisymmetric finite-element model S2D. The examined factors include: (1) the diameter of the infiltration ring, (2) the depth of water in the ring, (3) the depth of the ring insertion under the soil surface, (4) the size and the shape of the finite-element mesh near the ring wall, and (5) the double- vs. single-ring setup. The analysis suggests that the depth of the ring insertion significantly influences the infiltration rate. The simulated infiltration rates also exhibit high sensitivity to the shape of the finite-element mesh near the ring wall. The steady-state infiltration rate, even when considering a double-ring experiment, is significantly higher than the topsoil saturated hydraulic conductivity. The change of the water depth in the outer ring has only a small impact on the infiltration rate in the inner ring.