Yilmaz, D.; Lassabatere, L.; Moret-Fernandez, D.; Rahmati, M.; Angulo-Jaramillo, R.; Latorre, B.

Estimating of soil sorptivity ((Figure presented.)) and saturated hydraulic conductivity ((Figure presented.)) parameters by field infiltration tests are widespread due to the ease of the experimental protocol and data treatment. The analytical equation proposed by Haverkamp et al. (1994) allows the modelling of the cumulative infiltration process, from which the hydraulic parameters can be estimated. This model depends on both initial and final values of the soil hydraulic conductivity, initial soil sorptivity, the volumetric water content increase ((Figure presented.)) and two infiltration constants, the so-called (Figure presented.) and (Figure presented.) parameters. However, to reduce the number of unknown variables when inverting experimental data, constant parameters such as (Figure presented.) and (Figure presented.) are usually prefixed to 0.6 and 0.75, respectively. In this study, the values of these constants are investigated using numerical infiltration curves for different soil types and initial soil water contents for the van Genuchten-Mualem (vGM) soil hydraulic model. Our new approach considers the long-time expansions of the Haverkamp model, the exact soil properties such as (Figure presented.), (Figure presented.) and initial soil moisture to derive the value of the (Figure presented.) and (Figure presented.) parameters for each specific case. We then generated numerically cumulative infiltration curves using Hydrus-3D software and fitted the long-time expansions to derive the value of the (Figure presented.) and (Figure presented.) parameters. The results show that these parameters are influenced by the initial soil water content and the soil type. However, for initially dry soil conditions, some prefixed values can be proposed instead of the currently used values. If an accurate estimate of (Figure presented.) and (Figure presented.) is the case, then for coarse-textured soils such as sand and loamy sand, we propose the use of 0.9 for both constants. For the remaining soils, the value of 0.75 can be retained for (Figure presented.). For (Figure presented.) constant, 0.75 and 1.5 values can be considered for, intermediate permeable soils (sandy loam and loam) and low permeable soils (silty loam and silt), respectively. We clarify that the results are based on using the vGM model to describe the hydraulic functions of the soil and that the results may differ, and the assumptions may change for other models.

AtıfScopus12·OpenAlex10

İncele

Moret-Fernández, D.; Latorre, B.; Lassabatere, L.; Di Prima, S.; Castellini, M.; Yilmaz, D.; Angulo-Jaramilo, R.

The soil sorptivity, S, and saturated hydraulic conductivity, Ks, can be estimated from the inverse analysis of a cumulative infiltration curve using the quasi-exact implicit (QEI) formulation or its corresponding 4-Terms (4T) approximation. Although these models consider the soil as homogeneous media, there is no information about how heterogeneous profiles can affect the inferred soil properties. This work analyzes the influence of layered soils on Ks and S estimates using QEI and 4T models, and designs a new procedure for treating infiltration curves measured on layered soil profiles. The Sequential Infiltration Analysis (SIA) method considers a sequence of increasing time series from the cumulative infiltration data to estimate Ks and S, and its corresponding RMSE as a function of the number of samples used. A procedure to estimate the thickness of the upper uniform soil layer from the estimated wetting front advance (WFA) is also reported. The SIA method was applied on: (i) synthetic homogeneous profiles of loam soil and six layered profiles involving a 1, 2 and 3 cm thickness loam layer over silty or sandy loam soils, respectively, (ii) stratified laboratory soil columns, and (iii) 20 experimental infiltrations performed in a semiarid region of North-Eastern Spain. Similar results were found between QEI and 4T models for all cases. Erroneous estimates of Ks and S were observed when the total infiltration time series was considered for the analysis, regardless of the presence of soil layering. In opposite, estimates improved when the SIA method was applied to the layered systems. The SIA method exploits the fact that the RMSE increases when the wetting front reaches the interface between the soil layers. Such increase allows: (i) detection of the soil heterogeneity, (ii) determination of the infiltration time, to, required for the wetting front to reach the lower layer, and, (iii) accurate estimates of the upper layer Ks and S along with its thickness. Laboratory experiments on layered soils and field measurements demonstrated that the SIA method could be satisfactorily applied on different curves with contrasting shapes and magnitudes. Although soil layering encountered on most field samplings restricted the treatment of the observed infiltrations to short-medium times, the SIA method allowed robust estimates of Ks and S. These results indicate that the proposed method is a promising tool for characterizing the hydraulic properties of layered and heterogeneous soil profiles.

AtıfScopus19·OpenAlex18

İncele