Modeling the dynamics of seal formation and its effect on infiltration as related to soil and rainfall characteristics

Assouline, S.; Mualem, Y.

doi:10.1029/96wr02674

Cited by 124 publications

(110 citation statements)

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“…These soils were chosen because they are well characterized for infiltration, including having hydraulic properties of the respective seal layers that develop during exposure to rainfall [Assouline and Mualem, 1997;Assouline, 2004].…”

Section: Methodsmentioning

confidence: 99%

“…The van Genuchten [1980] expression for the water retention curve, and Mualem's [1976] model for the hydraulic conductivity function were used. In the case of the sealed soil profiles, the surface hydraulic properties used were those determined by Assouline and Mualem [1997] which employ the Brooks and Corey [1964] expression for the retention curve. The parameters for the van Genuchten [1980] model were determined by fitting retention data over the 0 to À200 cm capillary head range ( Table 1).…”

Section: Methodsmentioning

confidence: 99%

“…A special case of soil nonuniformity is when a seal layer develops at the soil surface due to the raindrop impacts [Assouline, 2004]. Infiltration through such nonuniform soil profiles was also modeled [Hillel and Gardner, 1970;Ahuja, 1983;Parlange et al, 1984;Baumhardt et al, 1990;Assouline and Mualem, 1997]. Recently, Chu and Marino [2005] have presented a modified Green and Ampt model that deals with infiltration into layered soils under unsteady rainfall.…”

Section: Introductionmentioning

confidence: 99%

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A simple accurate method to predict time of ponding under variable intensity rainfall

Assouline

Selker

Parlange

2007

Water Resources Research

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[1] The prediction of the time to ponding following commencement of rainfall is fundamental to hydrologic prediction of flood, erosion, and infiltration. Most of the studies to date have focused on prediction of ponding resulting from simple rainfall patterns. This approach was suitable to rainfall reported as average values over intervals of up to a day but does not take advantage of knowledge of the complex patterns of actual rainfall now commonly recorded electronically. A straightforward approach to include the instantaneous rainfall record in the prediction of ponding time and excess rainfall using only the infiltration capacity curve is presented. This method is tested against a numerical solution of the Richards equation on the basis of an actual rainfall record. The predicted time to ponding showed mean error 7% for a broad range of soils, with and without surface sealing. In contrast, the standard predictions had average errors of 87%, and worst-case errors exceeding a factor of 10. In addition to errors intrinsic in the modeling framework itself, errors that arise from averaging actual rainfall records over reporting intervals were evaluated. Averaging actual rainfall records observed in Israel over periods of as little as 5 min significantly reduced predicted runoff (75% for the sealed sandy loam and 46% for the silty clay loam), while hourly averaging gave complete lack of prediction of ponding in some of the cases.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A simple accurate method to predict time of ponding under variable intensity rainfall

Assouline

Selker

Parlange

2007

Water Resources Research

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“…Therefore, the seal layer is characterized by hydraulic properties that differ significantly from those of the underlying soil and by a thickness that can reach a few centimeters [26]. Consequently, the seal layer was found to affect infiltration [31,32], evaporation fluxes [33][34][35][36] and runoff [32,37,38]. The presence of a seal layer at the surface can complicate the calibration or the validation of RS missions, since the sensor's effective penetration depth lies mostly within the seal layer, whereas the soil moisture probe uses average soil moisture readings from both the seal layer and the undisturbed soil in the much thicker layer underneath.…”

Section: Introductionmentioning

confidence: 99%

Soil Surface Sealing Effect on Soil Moisture at a Semiarid Hillslope: Implications for Remote Sensing Estimation

2014

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Robust estimation of soil moisture using microwave remote sensing depends on extensive ground sampling for calibration and validation of the data. Soil surface sealing is a frequent phenomenon in dry environments. It modulates soil moisture close to the soil surface and, thus, has the potential to affect the retrieval of soil moisture from microwave remote sensing and the validation of these data based on ground observations. We addressed this issue using a physically-based modeling approach that accounts explicitly for surface sealing at the hillslope scale. Simulated mean soil moisture at the respective layers corresponding to both the ground validation probe and the radar beam's typical effective penetration depth were considered. A cyclic pattern was found in which, as compared to an unsealed profile, the seal layer intensifies the bias in validation during rainfall events and substantially reduces it during subsequent drying periods. The analysis of this cyclic pattern showed that, accounting for soil moisture dynamics at the soil surface, the optimal time for soil sampling following a rainfall event is a few hours in the case of an unsealed system and a few days in the case of a sealed one. Surface sealing was found to increase the temporal stability of soil moisture. In both sealed and unsealed systems, the greatest temporal stability was observed at positions with moderate slope inclination. Soil porosity was the best predictor of soil moisture temporal stability, indicating that prior knowledge regarding the soil texture distribution is crucial for the application of remote sensing validation schemes.

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“…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.…”

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confidence: 99%

Runoff from heterogeneous small bare catchments during soil surface sealing

Assouline

Mualem

2006

Water Resources Research

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[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...

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Modeling the dynamics of seal formation and its effect on infiltration as related to soil and rainfall characteristics

Cited by 124 publications

References 56 publications

A simple accurate method to predict time of ponding under variable intensity rainfall

A simple accurate method to predict time of ponding under variable intensity rainfall

Soil Surface Sealing Effect on Soil Moisture at a Semiarid Hillslope: Implications for Remote Sensing Estimation

Runoff from heterogeneous small bare catchments during soil surface sealing

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