Estimating lateral flow in double ring infiltrometer measurements

ABSTRACT

The steady infiltration rate of soil profiles is commonly determined for irrigation and soil conservation planning, but the divergence of methods reduces the reliability of measurements. In this study, the steady infiltration rate measured with a double ring infiltrometer (i_sr-dri) in different layers of a soil profile was compared between layers and with the steady vertical saturated flow rate estimated by the Richards equation (i_sr-hy). The measurements of i_sr-dri at the top of the A, E, and Bt horizons were compared to each other and also compared with the i_sr-hy to detect the occurrence of lateral flow in double ring infiltrometer measurements. The i_sr-dri in the A horizon (236 mm h^-1) was around 10 times higher than in the Bt horizon (20 mm h^-1), which implies in a lateral flow of almost 90 % in the surface horizon. The occurrence of lateral flow in double ring infiltrometer measurements was also shown by comparing i_sr-dri with the vertical saturated flow rate estimated with the Richards equation, i_sr-hy. The main conclusion is that i_sr-dri measured at the soil surface overestimates the steady infiltration rate of soil profiles when underlying horizons are less permeable and more restrictive to water flow. In these cases, the use of an effective saturated hydraulic conductivity of the soil profile would imply inaccurate planning of drainage, irrigation, and soil conservation designs.

steady infiltration rate; modeling; hydrus-1D