Runoff from heterogeneous small bare catchments during soil surface sealing

Abstract

[1] The combined effects of areal heterogeneity of the soil hydraulic properties and the surface seal formation dominate the hydrological response of arid and semiarid water catchments. Here these two phenomena were simulated to study their mutual role in runoff generation in small bare catchments. Seal formation during rainfall was simulated applying the dynamic model of Assouline and Mualem (1997). Areal heterogeneity of the soil was represented by a lognormal distribution of the saturated hydraulic conductivity of the initially undisturbed soil, K s , and by related distributions of the other soil parameters. The runoff hydrograph, at the outlet of a hypothetical bare catchment of 0.5 km 2 , was calculated using the cell model of Diskin et al. (1984). Two water catchments types, homogeneous and heterogeneous, with two different soil surface states, unsealed (mulched) and ongoing dynamic sealing, were considered. Four spatial organizations of the 10 cells in the heterogeneous catchment, all representing the same discrete distribution of K s , were studied. Rainfall events of two rainfall intensities, 20 and 40 mm h À1, of different durations ranging from 10 to 120 min, were applied uniformly over the catchments to study the effect of rainfall intensity and duration on runoff characteristics under the different soils and catchments conditions. The state of the soil surface seal was found to be a dominant factor with regard to runoff generation. Relative to the runoff produced in the homogeneous unsealed catchment under a (40 mm h À1 , 45 min) rainfall, the runoff was augmented by a factor of 10 during soil surface sealing and still more, by a factor of 20, when the soil surface was already sealed. On a relative basis the impact of soil sealing on runoff is much more important than that of soil heterogeneity. The effect of areal heterogeneity on runoff seems to depend on both the soil surface condition and the rainfall intensity and duration. When the soil is unsealed, the total runoff and the discharge peak are higher for the heterogeneous catchment. When the soil surface undergoes a sealing process, the total runoff and the discharge peak are higher for the heterogeneous catchment for the lower rainfall intensity of 20 mm h À1. For the 40 mm h À1 rainfall the catchment relative response was found to depend on the rainfall duration. A higher peak was obtained in the homogeneous catchment for rainfall durations above 60 min, and more runoff was produced for rainfall durations above 90 min. The spatial pattern of the cell organization in the heterogeneous catchment is an additional factor affecting the hydrological response. The hydrographs corresponding to each of four patterns representing the same areal heterogeneity displayed differences regarding concentration time (which varied between 7 and 28 min), timing of the peak runoff (varying between 77 and 146 min), and the peak discharge (varying between 0.41 and 0.57 m 3 s À1 ).Citation: Assouline, S., and Y. Mualem (2006), Runoff from heterogeneous small bare c...

Green-Ampt Infiltration Models for Varied Field Conditions: A Revisit

“…Recently, Craig et al (2010) developed a set of variants of the up-scaled GA model for calculating regionally averaged infiltration rates into heterogeneous soils which require specification of the spatial distribution of saturated hydraulic conductivity and/or initial soil water deficit in the sub-basin. A large body of literature established that the spatial variability of soil properties affect the infiltration at field scale (Smith and Hebbert 1979;Warrick and Nielsen 1980;Russo and Bresler 1982;Greminger et al 1985;Sivapalan and Wood 1986;Hawkins and Cundy 1987;Milly and Eagleson 1988;Binley et al 1989;Saghafian et al 1995;Logsdon and Jaynes 1996;Sullivan et al 1996;Woolhiser et al 1996;Merz and Plate 1997;Shin et al 1998;Smith and Goodrich 2000;Assouline and Mualem 2006). However, till now, the use of these techniques in practical applications is limited.…”

Spatio-temporal patterns in land use and management affecting surface runoff response of agricultural catchments—A review

“…Run-on infiltration reduces runoff volume and peak discharge (e.g. Corradini et al, 1998;Assouline and Mualem, 2006). Furthermore, mulch cover (e.g.…”

Statistical analysis and modelling of surface runoff from arable fields in central Europe

“…The mechanistic models may then be applied in a spatially distributed context including further processes occurring during runoff accumulation (for an extensive model overview see, e.g., Borah and Bera (2003); Migliaccio and Srivastava (2007); or the various results from the "distributed model inter-comparison project" (Smith et al, 2004)). Small-watershed-scale models dealing with surface runoff and soil erosion from arable land often stick to Hortonian-type surface runoff generation approaches (Assouline and Mualem, 2006;Fiener et al, 2008), assuming that surface sealing during heavy rainfall events dominates runoff generation on partly bare soils. Larger-scale models typically use Green and Ampt or Philip approaches assuming that infiltration is governed by a propagating wetting front depending on soil properties within the soil column (e.g.…”