Uncertainty of Hydraulic Conductivity under Field Conditions and at Fixed Pressure Heads and Water Contents
2005
Hurtado, A. L. B. | de Jong van Lier, Q.
Unsaturated hydraulic conductivity (K) can be expressed as a function of soil water content (θ) or pressure head (h). Methods to determine K often give highly variable results, thus making it difficult to report values for K in a reliable manner. Due to the sensitivity of pore conductivity to pore radius, it can be expected that K expressed as a function of h shows less variability than expressed as a function of θ. To test this hypothesis, K was determined at several values of θ and h using the instantaneous profile method at 48 locations in the surface and a subsurface layer of a Typic Hapludox in Brazil. Results were analyzed considering the field values of K at the time of observation (K ₜ), at fixed values of θ (K θ), and at fixed values of h (Kₕ). Results show that the coefficient of variation of K θ is higher than that of Kₕ, especially in the surface layer, which suggests that, if one has the choice, it would be preferable to estimate soil water movement using measured h values, and using K(h), instead of measuring θ and using K(θ). We also show that the variability in K ₜ increases as the soil gets drier, while Kθ and Kₕ show more variability for wetter soil.
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