A novel double disc method to determine soil hydraulic properties from drainage experiments with tension gradients

• This method estimated K s , θ n and α dr of a soil column by inverse analysis. 1D infiltration followed successive steady-states drainages were measured. The drainage curves are generated differential h between the top bottom. was tested on 2.5 cm high synthetic experimental columns. Accurate estimates obtained. Determination saturated hydraulic conductivity, water retention curve, θ(h) is paramount importance to characterize behavior vadose zone. Given van Genuchten model, defined residual, r saturated, volumetric content parameters, this work presents new laboratory procedure estimate for process, from analysis tension-gradient surface base column. To end, double disc system, one connected bubbling tower placed at second under core, employed. an air-vacuum system. experiment presented two parts: first downward saturation dry column, steps. During tension upper lower discs varied 0 -5 cm, -100 respectively. sorptivity, S calculated transient measure, Darcy’s law, optimized steady-state wetting w previously obtained . Once estimated, minimizing Q = b - objective function, where tensions core. value, optimimum computed as value that provides minimum By repeating process sequence different -isolines obtained, each which crossing-point corresponded actual values. columns four soils. Next, it applied sand 5 height filled with sieved loam, clay loam soil. compared corresponding values measured in same soils pressure plate technique contrasted empirical hysteresis model. method, fast (from 1 2 hours) easy implement small-scale experiments, successfully samples allowed explore range cm. Overall, accurate both A significant relationship also