Prediction of hydraulic conductivity of soils from particle-size distribution

Abstract

The study deals with the prediction of hydraulic conductivity, K, as a function of water content (0) of 12 soils of Andaman Islands, India, three each in clay loam, sandy clay loam, sandy clay and clay textures, from their particle-size distribution (PSD) data using the Arya-Paris model. Pore-size distribution of soils was derived from PSD data using the model and K(θ) was determined by the horizontal infiltration method. Twenty soils, five each with the above-mentioned textural classes were used to relate the pore flow rate (q) and the pore radius (r) using the parameters c and x as obtained from the Hagen-Poiseuille equation for an idealized porous medium. log(c) varied from -5.58 to 0.17 and x varied from 2.41 to 3.95, but no systematic trends were observed for the textural classes, except the value of x approaching 4 as the sand content in the samples increased. The model predicted unsaturated hydraulic conductivity with reasonable accuracy. The root mean square residuals (RMSR) of the log-transformed K(θ) for all textures ranged from 0.107 to 0.879. The intra- and inter-textural uncertainties in the prediction could be attributed to the heterogeneity in the observed (experimental) data, which originated from the difference in hydrophysical behaviour of the soils.