Infiltration Curve Research Articles

Parameter Estimation and Assessment of Infiltration Models for Madjez Ressoul Catchment, Algeria

Evaluation and modeling of soil water infiltration are essential to all aspects of water resources management and the design of hydraulic structures. Nonetheless, research focused on experimental studies of infiltration rates in arid and semi-arid regions under unknown boundary conditions remains minimal. This paper investigates the characteristics of the spatial variability of infiltration over a semi-arid rural basin of Algeria. The experiments were conducted using a portable double-ring infiltrometer filled at an equal volume of approximately 100 L of water for each of the 25 catchment locations. Soil moisture contents at the proximity of each test location were evaluated in the laboratory as per the standard NF P94–050 protocol. The experimental results are used to produce the catchment infiltration curves using three statistically fitted infiltration models, namely Horton, Kostiakov, and Philip models. The reliability of the models was assessed using four performance criteria. The statistical regressions of the fitted models suggest that the Horton model is the most suitable to assess the infiltration rate over the catchment with mean coefficients of Nash = 0.963, CC = 0.985, RMSE = 1.839 (cm/h), and Bias = 0.241. The superiority of the Horton model suggests that the initial and final infiltration rates, primarily affected by soil type, initial soil moistures, and land cover, are important predictors of the modeling process over the Madjez Ressoul catchment. The results also infer that the applicability of other models to the different types of undeveloped soils in the study area requires advanced field investigations. This finding will support the understanding of the hydrologic processes over semi-arid basins, especially in advising crop irrigation schemes and methods and managing the recurring flood and drought over the country.

Effects of residual film density and area on water accumulation infiltration amount of soil

With continuous increases in the amount and duration of plastic film used, the residual film in farmland soil is accumulated and tended to be fragmented, which affects soil water infiltration. We carried out an experiment of one-dimensional vertical infiltration of soil moisture. We examined the effects of different residual film density and area on soil water cumulative infiltration under 21 experimental treatments with 5 residual film area levels (0.25, 0.5, 1, 2, 8 cm2) and 5 residual film density levels (0, 60, 180, 300, 420 kg·hm-2). The results showed that soil water infiltration rate was accelerated and the total infiltration amount was increased by adding a certain amount of residual film into the clay loam soil with bulk density of 1.53 g·cm-3. The total infiltration amount of different residual film area always appeared mutation or turning point when the single residual film area was 1 cm2. When the residual film area and density were larger or smaller than that, the cumulative infiltration amount would be significantly affected, with the treatment of 0.5 cm2 residual film area and 200 kg·hm-2 residual film density being obvious demarcation. When the residual film area was 0.25 cm2, the cumulative infiltration reached the maximum. When the residual film with a single area ≤0.25 cm2 was uniformly mixed into the soil, the slope of soil water cumulative infiltration curve was significantly different from that of other residual film treatments, forming a "new structure" soil with unique water infiltration characteristics.

On shapes of cumulative infiltration curves

Water infiltration into soil is the key process in the water cycle, and understanding and predicting infiltration is essential for water management. Measurements of cumulative infiltration are a common part of soil hydrological characterization. Such measurements provide the cumulative infiltration curve (CIC), i.e. dependence of the amount of infiltrated water on time. The classic, usually anticipated CIC shape is the concave increase section transitioning to the linear section. However, other shapes were also observed. The objectives of this work were (a) to use the unique large international infiltration database SWIG to define distinctly different types of CIC shapes, and (b) to see if basic soil properties, land use, and infiltration measurement method can indicate what type of non-classic CIC shapes can be expected in site-specific conditions. Examination of 5023 CIC led to the definition of 12 types of CIC shapes. About 1/3 of SWIG datasets had non-classic CIC shapes. The shape types were visually discernible in most cases. A technique was suggested to distinguish the shape types if needed. The classification tree divided all datasets with non-classic CIC shapes into most similar inside and most different from each other groups. The infiltration measurement method, the clay content, and the organic carbon content were the most influential predictors of the shape type in this classification. Several non-classic shapes were previously related to soil structure and hydrophobicity. The relatively large fraction of non-classic CIC indicates the need to design infiltration experiments accounting for possible non-classic CIC, and the need for the cautious application of common infiltration equations, most of which were developed to simulate classic CIC shapes.

A Mathematical Approach for Determining the Soil Water Infiltration Curve

A Mathematical Approach for Determining the Soil Water Infiltration Curve

Effects of crude oil pollution on soil moisture infiltration with loessial soil and aeolian sandy soil

Crude oil may block soil pores, affect soil water repellency, and change soil water movement. In this study, soil column simulation was used to study the effects of different crude oil pollution levels (0, 0.5%, 1%, 2%, 4%) on the water infiltration processes in loessial soil and aeolian sandy soil. The results showed that soil wetting front speed and infiltration rate of those two soils decreased with increasing crude oil content. The time needed for wetting front reaching the bottom of the soil column was the longest under 4% crude oil polluted soil, which was 4 times and 48 times longer than that of no crude oil polluted soil for loessial soil and aeolian sandy soil, respectively. The cumulative infiltration of loessial soil decreased with increasing crude oil content, while it increased to the max and then decreased as the crude oil content increased in aeolian sandy soil. The cumulative infiltration curves of aeolian sandy soil with high crude oil contents (2% and 4%) presented "up-tail" phenomenon. Kostiakov infiltration model and Philip infiltration model could better fit the infiltration process than Green-Ampt model for loessial soil with different crude oil content. However, the two models could only well fit the infiltration process for aeolian sandy soil with low crude oil content (0, 0.5%, 1%). Crude oil pollution could significantly affect soil water infiltration process, especiall in aeolian sandy soil.

Research on the infiltrations in an earth dam. Case study: Cuibul Vulturilor Reservoir, Vaslui County, Romania

The dam of the reservoir Cuibul Vulturilor, located on the Tutova river is an inhomogeneous earth dam with a maximum height of 15.0 m, with a clayey central core and lateral prisms made of clayey-dusty sands. For tracking the evolution of body dam seepage, 12 piezometers and a drainage pipe with discharge in the downstream connection channel of the bottom outlet are used. The paper presents the characteristic elements of the theoretical infiltration curve in the dam It also shows the hydro isohypses for the dam drawn with SURFER program, using the maximum hydrostatic levels in the piezometers measured in the year 2019. The distribution of the hydro isohypses across the dam is strongly influenced by the location of the piezometers and the other point of measuring the hydraulic head. The pattern circulation of the infiltration water inside the dam body could be studied with increased accuracy, if the dam had been equipped with several piezometers. Even in these conditions, it is clearly observed that the regime of infiltrations through the dam body is similar to the theoretical way of behavior.

Smartphone-based tension disc infiltrometer for soil hydraulic characterisation

The tension disc infiltrometer has become a widespread method to measure soil hydraulic properties under unsaturated conditions. Although several automated devices have been developed, most designs include an elongated water reservoir and a pressure transducer with electronic components to register the water level, increasing its cost and limiting its application. The objective of this work is to present a new tension disc infiltrometer with a compact design of 10 cm diameter and height, where the water level is monitored by a smartphone camera. The infiltration curve is determined from the automated analysis of the images recorded by the smartphone without additional electronic components. The device was first validated in the laboratory by comparing visual measurements (V), the camera imagery (Ca) and a pressure transducer (PT). Next, it was tested on field infiltration experiments. Robust fits (R2 = 0.99) were found between the water level measured with Ca in the laboratory and those obtained with V and PT procedures. The Ca method is accurate, robust and independent of the relative camera position. Good fits were also observed between Ca water level and those obtained with PT in the field experiments. Similar hydraulic conductivity and sorptivity values were obtained with both sensors using the numerical solution of the Haverkamp (NSH) equation. The compact infiltrometer, in conjunction with the smartphone camera, is an accurate, accessible, portable and easy-to-use field-based device for soil hydraulic characterisation.

Sequential infiltration analysis of infiltration curves measured with disc infiltrometer in layered soils

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.

Simplified characteristic time method for accurate estimation of the soil hydraulic parameters from one‐dimensional infiltration experiments

AbstractRecently, a novel approach with excellent performance based on the concept of the characteristic infiltration time, the characteristic time method (CTM), is proposed to infer soil sorptivity (S) and saturated hydraulic conductivity (Ks) from one‐dimensional (1D) cumulative infiltration. The current work provides a simplified version of the CTM, called the SCTM, by eliminating the necessity of the iteration method used in CTM and providing a similar accuracy as the original method when estimating S and Ks. We used both synthetic and experimental data to evaluate SCTM in comparison with the original CTM, as well as Sharma (SH) and curve‐fitting methods. In the case of synthetically simulated infiltration experiments, the predicted S and Ks values showed an excellent agreement with their theoretical values, with Nash–Sutcliffe (E) values higher than 0.9 and RMSE values of 0.11 cm h1/2 and 0.35 cm h–1, respectively. In the case of experimental data, the SCTM showed E values larger than 0.73 and RMSE values of 0.64 cm h1/2 and 0.35 cm h–1, respectively. The accuracy and the robustness of SCTM was comparable with the original CTM when applied on synthetic infiltration curves as well as on experimental data. Similar to the original CTM, the simplified approach also does not require the knowledge of the time validity, which is needed when using approaches based on Philip's infiltration theory. The method is applicable to infiltrations with durations from 15 min to 24 h. The supplemental material presents the calculation of S and Ks using SCTM in an Excel spreadsheet.

Soil water infiltration under different land use conditions: in situ tests and modeling

ABSTRACT The efficiency and suitability of different models to estimate infiltration rates in Ferralic Arenosols and Rhodic Ferralsols in southern Brazil are evaluated in this paper. The influence of nine types of land use and soil management practices on infiltration modeling is also assessed. Model parameterization was performed fitting 42 experimental infiltration curves obtained by in situ tests with a double-ring infiltrometer. Soil characterization was also performed in laboratory. The results were assessed using basic statistical descriptors and model accuracy indicators (Nash and Sutcliffe efficiency coefficient and root mean square error). The investigated models satisfactorily simulated the infiltration rates and the most accurate model was modified Kostiakov, followed by the Horton; Singh and Yu; modified Holtan; Holtan; Philip; Green and Ampt/Mein and Larson and Kostiakov. Different types of land uses and soil management practices significantly affect the infiltration rates, mainly those combination with great presence of macroporosity that resulted in an erratic infiltration behavior and affected the infiltration model accuracy.

Three‐ and four‐term approximate expansions of the Haverkamp formulation to estimate soil hydraulic properties from disc infiltrometer measurements

AbstractSoil sorptivity, S, and saturated hydraulic conductivity, Ks, can be estimated from the inverse analysis of a disc infiltrometer cumulative infiltration curve using the quasi‐exact implicit (QEI) analytical Haverkamp et al. (1994) equation, which is a function of Ks, S, the parameters β and γ, the disc radius, rd, and the water content increase, ∆θ. Given the complexity of solving QEI, this paper presents three‐term, 3T, and four‐term, 4T, QEI expansions to estimate S and Ks. The interplays between β, γ, Ks and S employing S‐Ks, γ‐Ks, γ‐S, γ‐β, S‐β and Ks‐β error maps generated for a loam soil synthetic infiltration were analyzed with QEI. To reduce the number of variables, Δθ, rd and γ were packed into the term. Five different QEI expansion analyses were evaluated: (i and ii) optimization of 3T using A, 3TA, or β, 3Tβ, as fixed variables; (iii and iv) optimization of 3T, 3TAβ, and 4T, 4TAβ, using constant β and A values; and (v) optimization of 4T leaving all coefficients free, 4TF. The different methods were evaluated with synthetic infiltrations for homogeneous sand, loam and silt soils, and for an uniform loam soil with a contact sand layer. The QEI expansions were applied to experimental infiltrations, and the results were compared to those obtained with QEI, using β = 0.6 and γ = 0.75. Infiltrations were performed at zero cm of soil tension. Global optimization with QEI demonstrates that γ and β are extremely linked. This makes it difficult to estimate these two parameters. All procedures applied to synthetic homogeneous soils resulted in good Ks and S approaches. However, only 3TA, 3TAβ and 4TAβ obtained accurate estimates of Ks and S when applied to a synthetic homogeneous soil with a contact sand layer. Application of the different methods to the experimental infiltrations showed that 3TAβ and 4TAβ gave the most accurate and robust estimates of S and Ks.

Fractal analysis of the infiltration curve and soil particle size in a semi‐humid watershed

AbstractAlthough fractal mathematics has been commonly used to quantify particle size distribution (PSD), limited attention has been paid to the fractal dimension of the infiltration curve (DI). Therefore, it is necessary to determine whether the DI and fractal dimensions of PSD (Dm, Dclay, Dsilt and Dsand) can reflect the infiltration process, and soil erodibility and degradation. Accordingly, this study aimed to provide new information on the quantification of infiltration processes, and soil erodibility and degradation, using DI and Dm in the Soorak basin in the northern part of Iran. The soil and infiltration properties were calculated by field and laboratory practices on 46 topsoil samples and 34 infiltrometer double‐ring tests. Correlation, regression and redundancy analysis (RDA) were used to identify relationships between the infiltration curve and PSD coordinates with soil and infiltration properties. Results indicated that the DI was significantly linearly correlated with other infiltration curve characteristics, with the correlation coefficient ranging from −0.737 to −0.403 (sig. = 0.000–0.037). However, there was no significant correlation between DI and Dm, Dclay, Dsilt and Dsand. Different erodibility factors, especially KUSLE, had significant relations with Dm, Dclay, Dsilt, Dsand and DI (p < .01), suggesting that these fractal dimensions are indicators of soil degradation. Other findings indicated that the land use had no significant effect on DI and infiltration properties, whereas KUSLE, Dm, Dclay, DSilt and DSand were significantly affected by land‐use patterns (p < .01). These findings demonstrate that fractal dimensions of PSD and infiltration can be practicable indices to analyse soil degradation under different land‐use types.Highlights How fractal geometry adds to understanding of the infiltration process and soil degradation. Fractal dimensions of infiltration (DI) can describe the infiltration process. Fractal dimensions of soil (Dm) and DI can be used as indicators of the soil erodibility. Erodibility and fractal properties of soil were significantly affected by land use.

Water infiltration in a cracked soil considering effect of drying-wetting cycles

Infiltration is of great concern in many fields like hydrology, agriculture as well as geotechnical and geological engineering. This study aims to investigate water infiltration in a cracked soil. Infiltration tests were conducted on compacted soil samples with different cracking degrees by drying to various water contents. Three drying-wetting cycles were applied. Experimental results show that no desiccation cracks are observed in the first drying process while cracks initiate and propagate in the second and third drying processes. Different from the infiltration curve of the non-cracked soil sample consisting of two distinct stages, that of the cracked soil consists of three distinct stages, representing constant, rapid reduction and gradual reduction in infiltration rate, respectively. A modified equation is proposed to describe the infiltration behavior of a cracked soil considering the prehealing time of cracks. Furthermore, it is found that for the tested soil, 4% of surface crack ratio is a critical value. When surface crack ratio is smaller than the critical value, its influence on infiltration capacity is insignificant. Afterwards, the infiltration capacity increases dramatically with increasing surface crack ratio. Based on this observation, a piecewise function is proposed to characterize the relationship between the normalized infiltration capacity of cracked soil and surface crack ratio. Infiltration capacity also increases with decreasing initial water content and increasing number of drying-wetting cycles. In terms of steady final infiltration rate, it increases with increasing initial water content as well as increasing number of drying-wetting cycles, but is not affected by desiccation cracking.

Mathematical Model for Unsteady Flow Filtration in Homogeneous Closing Dikes

Adike is a barrier used to regulate or hold back water from a river, lake, or even the ocean. The performance of the dikes depends on various factors such as seepage area, height of seepage area, length of dike, filtration rate, etc. Our article considers filtration calculations of a homogeneous closing dike by determining the instantaneous filtration flow rate and seepage area and proposes a mathematical model to optimize the efficiency of dikes. It is known that the value of the height of seepage area (break in the depression curve) can be obtained from the equation of the Boussinesq initial and final boundary problem for a solitary flow wave. Further, it is proved experimentally by using closing dikes made of temporary hydraulic structures. The motion of the filtration stream is stabilized when the depression curve reaches the steady-state configuration, that is, when the flow wave travels a distance equal to the closing dike length. If the length of closing dike is large enough so that the outcrop point of the depression curve has sufficient time to reach the downstream, then there is no possibility for the formation of seepage area. If the length of closing dike is small, then the outcrop point does not have time to reach the downstream and so seepage area is formed. To avoid and solve this problem, the angular point of the depression curve and the finite period of seepage area formation are used. The stationary positions of the depression curve in a rectangular closing dike are obtained that results in an instantaneous monotonic (in the absence of infiltration and evaporation) curve, which is tangent to outcrop point in the downstream side and the initial water level inside the closing dike.

Hydraulic properties characterization of undisturbed soil cores from upward infiltration measurements

Estimation of the α and n van Genuchten (1980) parameters and the saturated hydraulic conductivity, Ks, of undisturbed soil samples is critical for realistic water flow simulations in the vadose zone. Given the Latorre and Moret-Fernández (2019) method, which allows estimating Ks, α and n from the inverse analysis of a single upward infiltration, the objective of this work is to advance on the theoretical understanding of this method and to apply it on undisturbed soil cores. To this end, the influence of the saturated, θs, and residual, θr, water content and initial soil tension, hi, on the α, n and Ks optimization was first studied on synthetic soils. A procedure to simultaneously estimate θs, α, n and Ks, which consisted on optimizing α, n and Ks for a range of θs values, was proposed. To this end, α, n and Ks were optimized leaving each θs as a fixed value. The method was next applied to experimental curves measured from sieved and undisturbed soil cores of 50 mm high and diameter, sampled the last ones from three fields with different management: bare vs. under plant soil; agricultural soil under conservation vs. conventional tillage; and overburden soil from mine vs. topsoil formed by the original soil. Results showed that θs had an important effect on α, n and Ks optimization, where the minimum error within the selected θs interval corresponded to the theoretical θs. An important effect of hi on the optimization was also observed. However, this influence was omitted by using a hi value located in the θr region, where dθdh≈0. Under this assumption, θr only affected the θs optimization, which value varied with θr. A robust relationship (R2 = 0.99; p < 0.0001) was found between theoretical and optimized θs, Ks and α and n calculated for the synthetic soils. Thus, the method allowed estimating four of the five van Genuchten (1980) parameters. An absolute minimum was also observed when the method was applied on experimental infiltration curves. The θs measured gravimetrically on the undisturbed samples was, on average, 8.1% higher than the optimized one. Overall, the method allowed detecting significant differences (p < 0.05) in hydraulic properties between bare and under plant soils and among tillage treatments. The large variability found in the mine’s soils prevented to find significant differences within this scenario.

Modeling infiltration in surface irrigation with minimum measurement (study of USDA–NRCS intake families)

The US Department of Agriculture–Natural Resources and Conservation Service (USDA–NRCS) intake families, in spite of lacking localized field data, often provide sufficient information for the initial design, evaluation, or management of surface irrigation systems. Scaling as a tool to characterize soil water dynamics and obviates need for the measurements. The present research aims to scale nineteen equations of intake families presented in SIRMOD. To doing so, one of the intake families’ equations was selected as the reference curve and the scaling factor for each intake family equals to the depth of water infiltrated after the given time (ts) (e.g., the depth of water infiltration after 2 h) in the reference infiltration equation to depth of infiltrated water after the specified time intake families equation. The results showed that the selection of the reference infiltration curve is optional and each of the cumulative intake families might be selected as the reference curve. According to the results of surface irrigation evaluation in terms of application efficiency, deep percolation and runoff percentage, there is no difference between the use of the cumulative intake families’ equation and intake families curve obtained from the scaling process.

Modelling soil water infiltration variability using scaling

One of the most substantial and crucial parameters for irrigation in agriculture is water infiltration into the soil. Given the variability of soil properties, the infiltration characteristics also vary. The present study aims to model soil water infiltration using scaling. In the present research, a new approach for scaling the infiltration equation was developed and evaluated for 22 infiltration tests. In the new method, the scaling factor ( F s ) for each equation equals the depth of infiltrated water after the specified time ( t s ) in the reference infiltration equation. This new method was applied to Philip's equation and was compared with previous Philip equation scaling methods such as sorptivity coefficient ( α s ), transmissivity coefficient ( α A ), the optimal factor obtained using the least squares error ( α o p t ), geometric, arithmetic and harmonic mean α s and α A . Results showed that scaling using F s has the best match with measured data (R2 = 0.99, MBE = 0.0006 and RMSE = 0.001) when compared to other Philip equation scaling methods. Among scaling techniques from the literature, F s had the highest correlation with α o p t (R2 = 0.96). The proposed method applied to the Kostiakov–Lewis infiltration equation was also evaluated. The results of the scaling of the Kostiakov–Lewis equation showed that to use reference curve is optional and each of the infiltration curves can be used as reference curve. As a whole, the results of the proposed method showed that the cumulative infiltration curve can be obtained using minimum infiltration-time measurement data.

Estimating the macroscopic capillary length from Beerkan infiltration experiments and its impact on saturated soil hydraulic conductivity predictions

The macroscopic capillary length, λc, is a fundamental soil parameter expressing the relative importance of the capillary over gravity forces during water movement in unsaturated soil. In this investigation, we propose a simple field method for estimating λc using only a single-ring infiltration experiment of the Beerkan type and measurements of initial and saturated soil water contents. We assumed that the intercept of the linear regression fitted to the steady-state portion of the experimental infiltration curve could be used as a reliable predictor of λc. This hypothesis was validated by assessing the proposed calculation approach using both analytical and field data. The analytical validation demonstrated that the proposed method was able to provide reliable λc estimates over a wide range of soil textural characteristics and initial soil water contents. The field testing was performed on a large database including 433 Beerkan infiltration experiments, with the 99% of the experiments yielding realistic λc values. The generated λc values were then used in conjunction with four different methods for estimating saturated soil hydraulic conductivity, Ks. Estimated Ks values were close to those generated by a reference method, with relative error < 25% in nearly all cases. By comparison, assuming constant or soil-dependent λc values caused relative errors in Ks of up to 600%. Altogether, the proposed method constitutes an easy solution for estimating λc, which can improve our ability to estimate Ks in the field.

Utilização de métodos de campo e laboratoriais para estimação de propriedades hidrodinâmicas do solo

O solo é de suma importância na drenagem urbana, pois auxilia na retenção da água proveniente das chuvas, através da infiltração, e reduz o escoamento superficial que tem como consequência as inundações urbanas. Determinar as propriedades hidrodinâmicas do solo é essencial para compreender esses processos. As propriedades hidrodinâmicas do solo são determinadas pela curva de retenção da água no solo e a curva de condutividade hidráulica. A determinação das propriedades hidrodinâmicas do solo requer ensaios de campo e de laboratório bastante dispendiosos, oneram e demandam um longo tempo de execução. Desse modo, o objetivo desse trabalho é determinar as propriedades hidrodinâmicas do solo pelos métodos Beerkan e Função de Pedotransferência. O estudo foi realizado no Instituto Federal de Pernambuco, Campus Recife, constituindo-se das etapas de coleta de amostras, ensaios de campo e ensaios de laboratório. O perfil do solo dos pontos amostrais do local de estudo foi classificado como franco arenoso. As propriedades hidrodinâmicas do solo obtidos pelo método da Função de Pedotransferência estão coerentes com os observados na literatura e as curvas de retenção do solo e de condutividade hidráulica, apresentaram comportamento semelhante em todos os pontos analisados. Para o método Beerkan, foram determinados os parâmetros de forma e de normalização, apresentando valores aceitáveis comparados aos da literatura e além disso, as curvas de infiltração ajustadas, as curvas de retenção e condutividade hidráulica nos pontos analisados tiveram comportamentos semelhantes entre elas.

A new approach for studying vertical infiltration

The exact contribution of the pressure head gradient term during the vertical infiltration process, occurring in homogeneous porous media under zero ponding head, is determined analytically to advance the knowledge related to the infiltration phenomenon. This contribution is smaller than that of the horizontal infiltration by a factor at which is a measurable function of the infiltration time t, characteristic of each porous body. By adding to this contribution that of gravity, a new two-term analytical equation is formulated which exactly reproduces an available vertical cumulative curve and satisfies the physics governing infiltration process. The properties of at allow the derivation of an equation accurate for small and moderate t and of another one accurate for all t, including large values. By applying new methodologies, the values of the sorptivity and hydraulic conductivity are determined analytically from an available cumulative infiltration curve. Philip’s two-term equation, which does not satisfy the physical requirements at the upper extreme of t, and three other equations that do satisfy it, are examined in the light of the findings of the present work. The proposed equations are able to describe the vertical infiltration process and may be used to provide the hydraulic properties.