HR: 1340h
AN: H33C-0481    [Abstracts]
TI: Modeling Infiltration and Runoff During Soil Seal Formation: The Effect of Areal Heterogeneity of Soil Hydraulic Properties
AU: * Assouline, S
EM: vwshmuel@agri.gov.il
AF: A.R.O.- Institute of Soil, Water and Environmental Sciences, P.O.B. 6, Bet Dagan, 50250 Israel
AU: Mualem, Y
EM: mualem@agri.huji.ac.il
AF: Hebrew University of Jerusalem- Faculty of Agricultural, Food and Environmental Quality Sciences - Dept. of Soil and Water, P.O.B. 12, Rehovot, 76100 Israel
AB: The expected trends in climate change may affect rainfall-runoff relationships. In the case of small, bare watersheds, rainfall-infiltration-runoff relationships are determined by (i) the formation of a sealing layer at the soil surface due to the raindrops impact, (ii) the spatial variability of the soil hydraulic properties within the watershed. The combined effects of soil surface sealing and areal heterogeneity of the soil hydraulic properties on the hydrological response of small bare catchment are simulated. Seal formation during rainfall was simulated according to 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, Ks, and by related distributions of the other soil parameters. The cell-model of Diskin et al. (1984) was applied to compute the runoff hydrograph at the outlet of a hypothetical bare catchment of 0.5 km2. Homogeneous and heterogeneous soils, with two different surface conditions, unsealed (mulched) and dynamic sealing, were considered. In terms of infiltration, accounting for areal soil heterogeneity reduces the ponding time and the rate of infiltration decrease, while it increases the steady infiltration rate after a long exposure to rainfall. When soil surface sealing is considered, the ponding time is only slightly affected but significantly more runoff is produced. However, the effects of soil variability on the infiltration curve are reduced, compared to the unsealed field. Compared to the homogeneous unsealed catchment case, runoff during soil surface sealing was increased by a factor of 10, and by a factor of 20 when the soil surface was already sealed before rainfall begun. Accounting for catchment heterogeneity increased runoff. Soil surface sealing reduced the effect of catchment heterogeneity on runoff hydrograph. This effect was also reduced as rainfall intensity increased.
DE: 1836 Hydrologic budget (1655)
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting