Scaling hydraulic properties of a macroporous soil

Abstract. Macroporous soils exhibit significant differences in their hydraulic properties for different pore domains. Multimodal hydraulic functions may be used to describe the characteristics of multiporosity media. I investigated the usefulness of scaling to describe the spatial variability of hydraulic conductivity (K(-h)) functions of a macroporous soil in Las Nutrias, New Mexico. Piecewise-continuous hydraulic conductivity functions suitable for macroporous soils in conjunction with a hybrid similar media-functional normalization scaling approach were used. Results showed that gravity-dominated flow and the related hydraulic conductivity (K(-h)) functions of the macropore region are more readily scalable than capillary-dominated flow properties of the mesopore and micropore regions. A possible reason for this behavior is that gravity-dominated flow in the larger pores is mostly influenced by the pore diameter which remains more uniform as compared to tortuous mesopores and micropores with variable neck and body sizes along the pore length. Introduction Near-saturated hydraulic properties of soil are important for predicting water flow in macroporous soil. Mohanty et al. [1997] showed the presence of bimodal hydraulic conductivity functions using disc infiltrometers and multistep outflow methods with detached soil cores at a field site in Las Nutrias, New Mexico. New multimodal piecewise-continuous functions were used to describe the K(-h) relationship for the macroporous soil: set measured using disc infiltrometers in an agricultural field near Ames, Iowa. In that study the saturated hydraulic conductivity (Ksat) at each measurement location (x) was found to be an ideal (physical) scale factor for K, while another empirical scale factor was estimated for h; all K(-h) data could then be coalesced to one unimodal Gardner-type function. In this paper we will investigate the suitability of scaling schemes for bimodal-type piecewise-continuous hydraulic conductivity functions of a macroporous soil in Las Nutrias, New Mexico. Experimental Methods The data used in this paper were taken from Mohanty et al