Macropores and water flow in soils

Abstract

This paper reviews the importance of large continuous openings (macropores) on water flow in soils. The presence of macropores may lead to spatial concentrations of water flow through unsaturated soil that will not be described well by a Darcy approach to flow through porous media. This has important implications for the rapid movement ot:• solutes and pollutants through soils. Difficulties in defining what constitutes a macropore and the limitations of current nomenclature are reviewed. The influence of macropores on infiltration and subsurface storm flow is discussed on the basis of both experimental evidence and theoretical studies. The limitations of models that treat macropores and matrix porosity as separate flow domains is stressed. Little-understood areas are discussed as promising lines for future research. In particular, there is a need for a coherent theory of flow through structured soils that would make the macropore domain concept redundant. Potential, Diameter, kPa tamNelson and Baver [1940] >-3.0

Estimation and upscaling of dual-permeability model parameters for the transport of E. coli D21g in soils with preferential flow

“…The occurrence of preferential flow is found to be the rule rather than the exception in most field soils (Flury et al, 1994;Singh and Kanwar, 1991), which may occur as a result of plant roots, burrowing earthworms, cracks, or natural structural heterogeneities (Beven and Germann, 1982;Cey et al, 2009;Madsen and Alexander, 1982;Unc and Goss, 2003;Wollum and Cassel, 1978). Preferential flow has been identified as a major problem hampering accurate predictions of contaminant transport in soils because of difficulty in quantifying the physical and chemical complexities of the soil matrix and macropore system (Šimůnek et al, 2003).…”

A review of model applications for structured soils: a) Water flow and tracer transport

“…A kinematic wave (KW) one-region model (Beven and Germann, 1982;Germann, 1985) is based on the boundary layer flow theory and was used for describing PF (e.g., Di Pietro, 1996, 1999). The KW model assumes that the wetting front proceeds by convective film flow in the mobile region and does not exchange water with the immobile region.…”

“…Overviews of the relevant processes and conditions triggering PF in soils are discussed in the classic paper by Beven and Germann (1982) and in the recent review by Jarvis (2007) which covers the stateof-the-art in our understanding of PF and (agro-) chemical transport, and the effects of soil and crop management practices. The latter is also treated in another recent review (Ma et al, 2007).…”

Décomposition chimique et isotopique d'un hydrogramme de crue d'un torrent méditerranéen - Réflexions méthodologiques

“…Les caractéristiques du bassin-versant sont d'ailleurs celles qui, théoriquement, permettent un écoule-ment hypodermique important : versants convexes profondément incisés et horizon de surface à forte conductivité hydraulique saturée (FREEZE, 1972). De surcroît, l'existence de conduits préférentiels permet un écoulement hypodermique rapide et important (HEWLETT, 1961 ;MOSLEY, 1979;BEVEN et GERMANN, 1982).…”