Saturated and near-saturated surface soil hydraulic properties influence the partition of rainfall and snowmelt into infiltration and runoff. The goal of this study was to characterize near-saturated surface soil hydraulic properties and water-conducting porosity in sloping landscapes. The specific objectives included exploration of tension and double-ring infiltrometers for estimation of soil hydraulic properties in sloping landscapes, development of an improved method for determining water-conducting porosity, and the application of these methods in characterizing soil hydraulic properties and water-conducting porosity under three land use. Water infiltration from a double-ring infiltrometer and a tension infiltrometer at water pressures between -2.2 and -0.3 kPa was measured in a cultivated field with 0, 7, 15, and 20% slopes at Laura and under three land use (native grass, brome grass and cultivated) at St. Denis in Saskatchewan, Canada. Three-dimensional computer simulation studies were also performed for tension infiltrometer with various disc diameters, water pressures, and surface slopes. Steady infiltration rates and estimated field-saturated hydraulic conductivity (Kfs), hydraulic conductivity-water pressure relationship (K(h)), and inverse capillary length parameter were compared for different slopes and land use. These parameters were not significantly different (p<0.05) among slopes. For specific K(h) functions, a new analytical solution was developed and compared with existing methods for calculating water-conducting porosity. The new method reliably determined water-conducting porosity of surface soils and gave consistent results, regardless of the width of water pressure ranges. At the -0.3 kPa water pressure, hydraulic conductivity of grasslands was two to three times greater than the cultivated lands. Values of inverse capillary length parameter were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0.04% and 0.01% of the total soil volume, respectively. Over 40% and 50% of the total water flux at -0.06 kPa water pressure was transmitted through macropores (pores > 1×10-3 m in diameter) of the cultivated land and the grasslands, respectively. Experimental and simulation results of this study indicated that both tension and double-ring infiltrometers are suitable for characterization of saturated and near-saturated surface soil hydraulic properties in landscapes up to 20% slope. The new method can be used to characterize water-conducting porosity from in situ tension and double-ring infiltrometers measurements more adequately and efficiently than the existing methods. Application of these methods for three land use indicated that land use modified surface soil hydraulic properties and consequently may alter the water balance of an area by affecting the partition between, and relative amount of infiltration and surface runoff.

Saturated and near-saturated surface soil hydraulic properties influence the partition of rainfall and snowmelt into infiltration and runoff. The goal of this study was to characterize near-saturated surface soil hydraulic properties and water-conducting porosity in sloping landscapes. The specific objectives included exploration of tension and double-ring infiltrometers for estimation of soil hydraulic properties in sloping landscapes, development of an improved method for determining water-conducting porosity, and the application of these methods in characterizing soil hydraulic properties and water-conducting porosity under three land use. Water infiltration from a double-ring infiltrometer and a tension infiltrometer at water pressures between -2.2 and -0.3 kPa was measured in a cultivated field with 0, 7, 15, and 20% slopes at Laura and under three land use (native grass, brome grass and cultivated) at St. Denis in Saskatchewan, Canada. Three-dimensional computer simulation studies were also performed for tension infiltrometer with various disc diameters, water pressures, and surface slopes. Steady infiltration rates and estimated field-saturated hydraulic conductivity (Kfs), hydraulic conductivity-water pressure relationship (K(h)), and inverse capillary length parameter were compared for different slopes and land use. These parameters were not significantly different (p<0.05) among slopes. For specific K(h) functions, a new analytical solution was developed and compared with existing methods for calculating water-conducting porosity. The new method reliably determined water-conducting porosity of surface soils and gave consistent results, regardless of the width of water pressure ranges. At the -0.3 kPa water pressure, hydraulic conductivity of grasslands was two to three times greater than the cultivated lands. Values of inverse capillary length parameter were about two times and values of Kfs about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0.04% and 0.01% of the total soil volume, respectively. Over 40% and 50% of the total water flux at -0.06 kPa water pressure was transmitted through macropores (pores > 1×10-3 m in diameter) of the cultivated land and the grasslands, respectively. Experimental and simulation results of this study indicated that both tension and double-ring infiltrometers are suitable for characterization of saturated and near-saturated surface soil hydraulic properties in landscapes up to 20% slope. The new method can be used to characterize water-conducting porosity from in situ tension and double-ring infiltrometers measurements more adequately and efficiently than the existing methods. Application of these methods for three land use indicated that land use modified surface soil hydraulic properties and consequently may alter the water balance of an area by affecting the partition between, and relative amount of infiltration and surface runoff.

In this study, a two phase investigation of the hydraulic conductivity parameters of silty soils was performed. In the first phase, double-ring infiltrometer tests were used to measure infiltration rates in-situ at two sites in the Piedmont physiographic province of Georgia. The efficacy of predicting saturated hydraulic conductivity for Piedmont soils via published soil surveys from the National Resource Conservation Service and pedotransfer functions was then investigated. Work focused on the development of a consistent test methodology for soils (sandy, to silts and clays) in the Piedmont, and the final test method utilized being the constant head test, using a double-ring infiltrometer with Mariotte tubes to maintain the head. In the second phase of the investigation, laboratory based measurements of the saturated hydraulic conductivity of binary mixtures of fine sand and nonplastic silt were performed to investigate the effects of particle mixtures on hydraulic conductivity. The materials used were ASTM 100/200 sand and Sil-Co-Sil 40 non-plastic silt, chosen based on the ratio of the mean particle diameters. Significant effort was invested in the development and comparison of methodologies to produce uniform specimens of the binary mixtures for hydraulic conductivity testing, with the final being modified dry tubing. Two fixed densities were used to investigate the effects of particle packing on the hydraulic conductivity of binary mixtures, with critical fines contents chosen to ensure the finer particles primarily filled the pore volume of the coarse particles. Incremental fines contents, by mass, up to this theoretical fines content were tested. The measured saturated hydraulic conductivity was evaluated in terms of fines content, global and intergranular void ratio, and confining stress. Models for predicting extreme void ratios and saturated hydraulic conductivity of binary mixtures were also investigated.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / O estudo teve como objetivo proceder a uma anÃlise comparativa de tÃcnicas para estimativa da infiltraÃÃo de Ãgua no solo, com vistas ao dimensionamento, manejo e avaliaÃÃo de sistemas de irrigaÃÃo por sulcos. O estudo foi conduzido no perÃodo de janeiro a fevereiro de 2006 na Ãrea AT1 da Fazenda Experimental Vale do Curu, Pentecoste, Estado do CearÃ, em um Neossolo FlÃvico de textura franco-arenosa. O delineamento experimental adotado foi o de blocos completamente casualizados, constando de cinco tratamentos e quatro repetiÃÃes. Os tratamentos constaram das seguintes tÃcnicas de infiltraÃÃo de Ãgua no solo: cilindro-infiltrÃmetro, sulco-infiltrÃmetro, entradasaÃda, balanÃo de volume I e balanÃo de volume II. A anÃlise dos resultados permitiu as seguintes conclusÃes: - A lÃmina de Ãgua infiltrada no solo apresentou um maior grau de dependÃncia à variÃvel preparo de solo se comparada à variÃvel teor de Ãgua no solo; - As tÃcnicas de balanÃo volumÃtrico apresentaram resultados semelhantes tanto no que diz respeito à lÃmina infiltrada acumulada quanto ao regime assintÃtico; - As tÃcnicas de entrada-saÃda e cilindro-infiltrÃmetro apresentaram valores de infiltraÃÃo acumulada superestimados se comparados aos demais tratamentos analisados; - As tÃcnicas de balanÃo volumÃtrico apresentaram um menor tempo de resposta à obtenÃÃo do regime assintÃtico, caracterÃstica inerente ao processo fÃsico da infiltraÃÃo de Ãgua no solo. / The study it had as objective to proceed to a comparative analysis of techniques for estimate of the water infiltration in the soil, with sights to the sizing, handling and evaluation of systems of irrigation for furrow. The study was lead in the period of January the February of 2006 in area AT1 of the Fazenda Experimental Vale do Curu, Pentecoste, Cearà State, in one Neossolo FlÃvico of sand loam texture. The adopted experimental delineation was randomized blocks design, consisting of five treatments and four replications. The treatments had consisted of the following techniques of water infiltration in the ground: cylinder infiltrometer, furrow infiltrometer, nflow-outflow, volume balance I and volume balance II. The analysis of the results allowed the following conclusions: - The water infiltrated in the soil presented a bigger degree of dependence to the variable soil tillage if compared with the variable text of water content. - The techniques of volumetric balance had presented resulted similar in what it says respect to the water infiltrated accumulated how much to the asymptotic regime, allowing to recommends the methodology preconized for Christiansen (1966) in situations where the use of the methodology of Walker and Skogerboe (1987) that if present limitation. - The techniques of inflow-outflow and cylinder infiltrometer had presented values of accumulated infiltration overestimated if compared with the too much analyzed treatments, above all to the methodologies of volumetric balance. - The techniques of volumetric balance had presented a lesser time of reply to the attainment of the asymptotic regime, characteristic inherent to the physical process of the water infiltration in the soil.

Los modelos numéricos son herramientas fundamentales para realizar predicciones de muchos problemas enfrentados por ingenieros geotécnicos y geoambientales. Sin embargo, para que estos modelos puedan realizar predicciones confiables, los parámetros de entrada del modelo deben ser estimados considerando el efecto escala. En este contexto, esta tesis se concentra en las reglas del cambio de escala de los parámetros de flujo y transporte de masa en un suelo tropical a través de estudios numéricos, de laboratorio y de campo. Esta está organizada en cuatro partes. Primero, la heterogeneidad, correlación y correlación cruzada entre los parámetros de transporte de solutos (dispersividad, ¿, y coeficiente de partición, Kd) y las propiedades del suelo fueron estudiadas en detalle. En esta parte fue verificado que la conductividad hidráulica (K) y los parámetros de transporte de solutos son altamente heterogéneos, mientras que las propiedades del suelo no lo son. La correlación espacial de ¿ y K con variables estadísticamente significativas fue estudiada. Este resultado probablemente podrá mejorar la estimación en casos de estudios de pequeña escala debido a que solo fue observada correlaciones de hasta 2,5 m. Este estudio fue un primer intento de evaluar la variación espacial en el coeficiente de correlación de los parámetros de transporte de un soluto reactivo y de un no reactivo, indicando las variables más relevantes y aquella que debería ser incluida en estudios futuros. En la segunda parte, el efecto escala en K, dispersividad y coeficiente de partición de potasio y clorito fue estudiado experimentalmente a través de experimentos de laboratorio y de campo. El objetivo de esta parte fue contribuir a la discusión sobre el efecto escala en K, ¿ y Kd, y entender como estos parámetros se comportan con el cambio de escala de medición. La dispersividad tiende a aumentar con la altura de la muestra de manera exponencial. El coeficiente de partición tiende a aumentar con la altura, el diámetro y el volumen de la muestra. Estas diferencias encontradas en los parámetros de acuerdo con la escala de medición deben ser considerados cuando estos valores sean usados posteriormente como datos de entrada de modelos numéricos; de otra manera, las respuestas pueden ser malinterpretadas. Tercero, análisis estocásticos tridimensionales de cambio de escala de la conductividad hidráulica fueron realizados usando los métodos de promedios simples y de Laplace con piel para una variedad de tamaños de bloques usando mediciones reales de K. En esta parte son demostrados los errores que pueden ser introducidos al usar métodos determinísticos de cambio de escala usando promedios simples de las mediciones de K sin llevar en consideración la correlación espacial. La aplicación muestra que la heterogeneidad de K puede ser incorporada en la práctica diaria del modelador geotécnico. Los aspectos que considerar durante un proceso de cambio de escala también son discutidos. Finalmente, la dependencia del exponente de la norma-p como función del tamaño del bloque fue analizada. En la última parte, una aplicación de cambio de escala estocástico del coeficiente de dispersión hidrodinámica D y del factor de retardo R fue realizada usando datos reales con el objetivo de reducir la falta de casos de investigación experimental de cambio de escala de parámetros de transporte de solutos reactivos. El cambio de escala de D fue realizado usando el método de macrodispersión. El método de promedio simple de norma-p fue usado para realizar el cambio de escala de R. Una buena propagación de incertidumbres fue alcanzada. Métodos simples de cambio de escala pueden ser introducidos en la práctica del modelaje usando programas comerciales de transporte y conseguir reproducir el transporte en escala gruesa, pero puede requerir correcciones con el objetivo de reducir el efecto de suavizado de la heterogeneidad causado por el / Numerical models are becoming fundamental tools to predict a range of complex problems faced by geotechnical and geo-environmental engineers. However, to render the model reliable for future predictions, the model input parameters must be determined with consideration of the scale effects. In this context, this thesis focuses on upscaling of water flow and mass transport in a tropical soil by means of numerical, laboratory and field studies. This thesis is organized in four parts. First, the heterogeneity, correlation and cross-correlation between solute transport parameters (dispersivity, ¿, and partition coefficient, Kd) and soil properties were studied in detail. In this part, it was verified that the hydraulic conductivity (K) and solute transport parameters are highly heterogeneous, while soil properties not. Spatial correlation of ¿, K, and statistically significant variables were studied, and it would probably improve the estimation only in a small-scale study, since the spatial correlation were only observed up to 2.5 m. This study was a first attempt to evaluate the spatial variation in the correlation coefficient of transport parameters of a reactive and a nonreactive solute, indicating the more relevant variables and the one that should be included in future studies. In the second part, scale effect on K, dispersivity and partition coefficient of potassium and chloride is studied experimentally by means of laboratory and field experiments. The purpose of was to contribute to the discussion about scale effects on K, ¿ and Kd and understanding how these parameters behave with the change in the scale of measurement. Results shows that K increases with scale, regardless of the method of measurement. Dispersivity trends to increases exponentially with the sample height. Partition coefficient, tend to increase with sample length, diameter and volume. These differences in the parameters according to the scale of measurement must be considered when these observations are later used as input to numerical models, otherwise the responses can be misrepresented. Third, stochastic analysis of three-dimensional hydraulic conductivity upscaling was performed using a simple average and the Laplacian-with-skin methods for a variety of block sizes using real K measurements. In this part it was demonstrated the errors that can be introduced by using a deterministic upscaling using simple averages of the measured K without accounting for the spatial correlation. The application shows that K heterogeneity can be incorporated in the daily practice of the geotechnical modeler. The aspects to consider when performing the upscaling were also discussed. Finally, the dependence of the exponent of the p-norm as a function of the block size was analyzed. In the last part, an application of stochastic upscaling of hydrodynamic dispersion coefficient (D) and retardation factor (R) was performed using real data aiming to reduce the lack in experimental upscaling of reactive solute transport research. Upscaling of D was done using macrodispersion method. Simple average method based on p-norm was used to perform R upscaling. A good propagation of the uncertainties was achieved. Simple upscaling methods can be incorporated to the modeling practice using commercial transport codes and properly reproduce de transport at coarse scale but may require corrections to reduce smoothing of the heterogeneity caused by the upscaling procedure. / Els models numèrics s'estan constituint en eines fonamentals per a realitzar prediccions d'una àmplia gamma de problemes enfrontats per enginyers geotècnics i geoambientales. No obstant açò, perquè aquests models puguen realitzar prediccions fiables, els paràmetres d'entrada del model han de considerar l'efecte escala. En aquest context, aquesta tesi es concentra en les regles del canvi d'escala dels paràmetres de flux i transport de massa en un sòl tropical a través d'estudis numèrics, de laboratori i de camp. Aquesta tesi està organitzada en quatre parts. Primer, l'heterogeneïtat, correlació i correlació creuada entre els paràmetres de transport de soluts (dispersivitat, ¿, i coeficient de partició, Kd) i les propietats del sòl van ser estudiades detalladament. En aquesta part va ser verificat que la conductivitat hidràulica (K) i els paràmetres de transport de soluts són altament heterogenis, mentre que les propietats del sòl no ho són. La correlació espacial de ¿ i K amb variables estadísticament significatives va ser estudiada. Aquest resultat probablement podrà millorar l'estimació en casos d'estudis de xicoteta escala a causa que solament va ser observada correlacions de fins a 2,5 m. Aquest estudi va ser un primer intent d'avaluar la variació espacial en el coeficient de correlació dels paràmetres de transport d'un solut reactiu i d'un no reactiu, indicant les variables més rellevants i aquelles que haurien de ser inclosas en estudis futurs. En la segona part, l'efecte escala en K, dispersivitat i coeficient de partició de potassi i clorito va ser estudiat experimentalment a través d'experiments de laboratori i de camp. L'objectiu d'aquesta part va ser contribuir a la discussió sobre l'efecte escala en K, ¿ i Kd, i entendre com aquests paràmetres es comporten amb el canvi d'escala de mesurament. La dispersivitat tendeix a augmentar amb l'altura de la mostra, és a dir, amb la longitud del transport, de manera exponencial. El coeficient de partició tendeix a augmentar amb l'altura, el diàmetre i el volum de la mostra. Aquestes diferències en els paràmetres d'acord amb l'escala de mesurament han de ser considerats quan aquests valors siguen usats posteriorment com a dades d'entrada de models numèrics; d'una altra manera, les respostes poden ser malament interpretades. Tercer, anàlisis estocàstiques tridimensionals de canvi d'escala de la conductivitat hidràulica van ser realitzats usant els mètodes de mitjanes simples i de Laplace amb pell per a una varietat de grandàries de blocs usant mesuraments reals de K. En aquesta part són demostrats els errors que poden ser introduïts en usar mètodes determinístics de canvi d'escala usant mitjanes simples dels mesuraments de K sense tindre en consideració la correlació espacial. L'aplicació mostra que l'heterogeneïtat de K pot ser incorporada en la pràctica diària del modelador geotècnic. Els aspectes a considerar durant un procés de canvi d'escala també són discutits. Finalment, la dependència de l'exponent de la norma-p com a funció de la grandària del bloc va ser analitzada. En l'última part, una aplicació de canvi d'escala estocàstic del coeficient de dispersió hidrodinámica D i del factor de retard R va ser realitzada usant dades reals amb l'objectiu de reduir la falta de casos de recerca experimental de canvi d'escala de paràmetres de transport de soluts reactius. El canvi d'escala de D va ser realitzat usant el mètode de macrodispersió. El mètode de mitjana simple de norma-p va ser usat per a realitzar el canvi d'escala de R. Una bona propagació d'incerteses va ser aconseguida. Mètodes simples de canvi d'escala poden ser introduïts en la pràctica de la modelació usant programes comercials de transport i aconseguir reproduir el transport en escala gruixuda, però pot requerir correccions amb l'objectiu de reduir l'efecte de suavitzat de l'heterogeneïtat causat pel procés de canvi d'escala. / Almeida De Godoy, V. (2018). Upscaling of water flow and mass transport in a tropical soil: numerical, laboratory and field studies [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/102405 / TESIS

The diploma thesis is focused on issues of measurement and evaluation of hydraulic characteristics of soil. In the literary research, the definitions of hydraulic conductivity and retention curve of soil moisture, their measurements in laboratory and field conditions and the prediction of these characteristics by using of pedotransfer functions. In the practical part of the diploma thesis, an evaluation of the hydraulic conductivity of soil from the experimental areas near the village Bohaté Málkovice. Two-cylindrical and mini-disc infiltration meters were used for field measurements, and a constant-gradient permeameter was used in the laboratory. Physical and empirical equations were used to evaluate the hydraulic conductivity. The results were processed numerically, tabulated and then compared.

O presente trabalho visa a quantificação do escoamento de água na interação entre rio e aqüífero subterrâneo em uma bacia, através da utilização de infiltrômetros e de poços de observação de lençol freático na proximidade do rio. O Ribeirão da Onça, um afluente do rio Jacaré-Guaçú localizado no município de Brotas no estado de São Paulo, foi escolhido para a realização deste estudo sendo a sua bacia hidrográfica pertencente a importante área de recarga do aqüífero Guarani. O estudo da interação rio aqüífero foi realizado através de infiltrômetros colocados em três seções deste rio. Analisando-se o comportamento da interação ao longo de um período de 7 meses, verificou-se que a taxa média de surgimento foi de 300 mm/dia na área de afloramento do lençol freático. Ainda, observou-se a influência da chuva e da pressão atmosférica nos valores do surgimento, sendo a última de forma inversa. Tendo em vista os resultados satisfatórios dos experimentos, a utilização de infiltrômetros para determinação da taxa de troca entre rio e aqüífero representa um procedimento simples e adequado, mas requer cuidados contínuos para obter-se resultados consistentes. / The purpose of this work is to quantify the river-aquifer interaction in a river basin through the use of infiltrometers and observation wells located on the banks. Onça Creek, a tributary of the Jacaré-Guaçú river in the state of São Paulo, was chosen for this study being located in the recharge area of the regional Guarani aquifer. Infiltrometers were placed at three sections in the bed of Onça Creek. Analyzing the behavior of the river-aquifer interaction during 7 months, it is found that the average exfiltration rate is of the order of 300 mm/day in the seepage area. Further, the seepage rate is found to be influenced by rainfall events, atmospheric pressure and rate of rise or fall of river stage. In view of the satisfactory experimental results obtained in this study, the use of infiltrometers for the determination of the river-aquifer interaction is recommended as a simple and sound procedure if due care is taken in their installation in the river bed.

O presente trabalho visa a quantificação do escoamento de água na interação entre rio e aqüífero subterrâneo em uma bacia, através da utilização de infiltrômetros e de poços de observação de lençol freático na proximidade do rio. O Ribeirão da Onça, um afluente do rio Jacaré-Guaçú localizado no município de Brotas no estado de São Paulo, foi escolhido para a realização deste estudo sendo a sua bacia hidrográfica pertencente a importante área de recarga do aqüífero Guarani. O estudo da interação rio aqüífero foi realizado através de infiltrômetros colocados em três seções deste rio. Analisando-se o comportamento da interação ao longo de um período de 7 meses, verificou-se que a taxa média de surgimento foi de 300 mm/dia na área de afloramento do lençol freático. Ainda, observou-se a influência da chuva e da pressão atmosférica nos valores do surgimento, sendo a última de forma inversa. Tendo em vista os resultados satisfatórios dos experimentos, a utilização de infiltrômetros para determinação da taxa de troca entre rio e aqüífero representa um procedimento simples e adequado, mas requer cuidados contínuos para obter-se resultados consistentes. / The purpose of this work is to quantify the river-aquifer interaction in a river basin through the use of infiltrometers and observation wells located on the banks. Onça Creek, a tributary of the Jacaré-Guaçú river in the state of São Paulo, was chosen for this study being located in the recharge area of the regional Guarani aquifer. Infiltrometers were placed at three sections in the bed of Onça Creek. Analyzing the behavior of the river-aquifer interaction during 7 months, it is found that the average exfiltration rate is of the order of 300 mm/day in the seepage area. Further, the seepage rate is found to be influenced by rainfall events, atmospheric pressure and rate of rise or fall of river stage. In view of the satisfactory experimental results obtained in this study, the use of infiltrometers for the determination of the river-aquifer interaction is recommended as a simple and sound procedure if due care is taken in their installation in the river bed.

MSCAGR / Department of Soil Science / Soil hydraulic and hydraulic-related physical properties are key to soil productivity and these properties are widely studied. Nevertheless, their spatial variability is least understood. Two sites were selected for this study (University of Venda Experimental farm and Roodeplaat, Agricultural Research Council farm). The objectives of this study were to determine the spatial variability of soil water content, water infiltration and hydraulic conductivity on selected soils. Field measurements were done on a 20 m × 20 m. Soil hydraulic and hydraulic-related physical properties were studied at two depths, 0 – 0.2 m top soil and 0.2 – 0.4 m sub soil. The field was irrigated to saturation and let to drain freely for two days. The soil was quickly secured in water cans to avoid further loss of water by evaporation and taken to the laboratory for analysis. Data was analysed using ordinary kriging method in ArcMap® software version 10.4 to generate spatial variability maps and semi variograms. The University of Venda Experimental farm had lesser spatial variability with coefficient of variation ranging from 9.6 to 33.4%. The spatial variability of soil was very low confirmed by contour maps depicting slightly homogeneity. Whereas, the soil hydro-physical properties displayed greater spatial variability at Roodeplaat, Agricultural Research Council Experimental farm. The empirical variograms of spherical model fits were also assuming weak spatial dependence with a curve variogram. The coefficient of variation ranged from 10.5 to 51.9%. Therefore, the greater variability at Roodeplaat, Agricultural Research Council Experimental farm indicated that coarse soil texture under conventional tillage has a greater influence on the spatial variability of the soil hydro-physical properties. / NRF

A função condutividade hidráulica é um dos parâmetros essenciais para o estudo do fluxo em solos não saturados, permitindo abordar, dentre outros, o avanço da frente de umedecimento e questões como a irrigação e drenagem de solos. Para determinar a condutividade hidráulica não saturada de um solo típico da região Centro-Oeste do Estado de São Paulo, utilizou-se o infiltrômetro de disco. Este equipamento permite conduzir a infiltração de água, estando esta sujeita a um potencial negativo. Com os dados de infiltração acumulada e tempo acumulado obtidos em cada ensaio, foi possível determinar os valores da condutividade hidráulica não saturada e sortividade. Os cálculos foram feitos por diferentes métodos para cada ensaio realizado com o infiltrômetro de disco e comparadas com resultados de ensaios utilizando o permeâmetro Guelph. Observou-se que as condutividades hidráulica não saturadas obtidas com o infiltrômetro de disco tenderam a valores próximos das fornecidas indiretamente por meio do permeâmetro Guelph, com dispersão de aproximadamente uma ordem de grandeza para cada sucção. Também se observou que a condutividade hidráulica não saturada tende a diminuir conforme aumenta a sucção imposta ao solo, mesmo considerando a estreita faixa de sucções usadas nos ensaios. Notou-se ainda pequena variação nas condutividades hidráulicas saturadas calculadas por meio do infiltrômetro de disco, por meio de medidas diretas utilizando o permeâmetro Guelph e ensaios de permeabilidade realizados em laboratório. / The hydraulic conductivity function is essential to the study of water flow in unsaturated soils. From function there can be derived the advancement of the humidification (saturation) front, among other parameters, which is essential to projects of irrigation and drainage of soils. A disk infiltrometer was used to determine the unsaturated hydraulic conductivity of a sample of typical soil from central São Paulo, Brazil. The disk infiltrometer apparatus conducts the infiltration water, which is held at negative potential. Data for cumulative infiltration and elapsed time for each test was used to determine values of unsaturated hydraulic conductivity and sorptivity. Different methodology was applied in the calculations. Data for each experiment carried out utilizing the disk infiltrometer was compared to data obtained utilizing the permeameter of Guelph. It was observed that the unsaturated hydraulic conductivity obtained through the disk infiltrometer yielded values near those obtained indirectly by the permeameter of Guelph, which showed dispersion approximately within one order of magnitude for each suctioning performed. Furthermore, it was observed that the unsaturated hydraulic conductivity tends to diminish in magnitude in an inverse relation to the suction pressure subjected by the soil, even after considering the narrow band of suction pressures carried out in the tests. It was further observed a small variation in the saturated hydraulic conductivities computed from data obtained directly from the infiltrometer disk, the permeameter of Guelph, and other permeability tests done in laboratory.