Porous Medium Typology Influence on the Scaling Laws of Confined Aquifer Characteristic Parameters

An accurate measurement campaign, carried out on a confined porous aquifer, expressly reproduced in laboratory, allowed the determining of hydraulic conductivity values by performing a series of slug tests. This was done for four porous medium configurations with dierent granulometric compositions. At the scale considered, intermediate between those of the laboratory and the field, the scalar behaviors of the hydraulic conductivity and the eective porosity was verified, determining the respective scaling laws. Moreover, assuming the eective porosity as scale parameter, the scaling laws of the hydraulic conductivity were determined for the dierent injection volumes of the slug test, determining a new relationship, valid for coarse-grained porous media. The results obtained allow the influence that the dierences among the characteristics of the porous media considered exerted on the scaling laws obtained to be highlighted. Finally, a comparison was made with the results obtained in a previous investigation carried out at the field scale

Use of fractal models to define the scaling behavior of the aquifers' parameters at the mesoscale

AbstractWe present an experimental study aiming at the identification of the hydraulic conductivity in an aquifer which was packed according to four different configurations. The conductivity was estimated by means of slug tests, whereas the other parameters were determined by the grain size analysis. Prior to the fractal we considered the dependence of the conductivity upon the porosity through a power (scaling) law which was found in a very good agreement within the range from the laboratory to the meso-scale. The dependence of the conductivity through the porosity was investigated by identifying the proper fractal model. Results obtained provide valuable indications about the behavior, among the others, of the tortuosity, a parameter playing a crucial role in the dispersion phenomena taking place in the aquifers

Influence of the scale range width on the determination of the hydraulic conductivity and effective porosity. The case of a porous aquifer in southern Italy

Abstract The importance of a law that, for an assigned porous medium, gives the variability of the hydraulic conductivity with the effective porosity is well known. Commonly this variability is represented by a power law at different scales, especially those of laboratory and field. Often it can be useful to have a scaling law valid for a single scale range, comprising both those of laboratory and field. Therefore investigation about the reliability of the laws representing the scaling behavior in the various intervals to which reference was made could be suitable. The purpose of this study is to provide evidence about the reliability of the scaling laws for laboratory, field and global (laboratory plus field) scaling ranges, verifying consistency with the expected proportionality between hydraulic conductivity and effective porosity for each of these. This verification was carried out using power-type scaling laws to two and four parameters respectively, and performing suitable moving averages of original data sets, in an attempt to reduce the inevitable measurement uncertainties. The experimental results, obtained with reference to the confined aquifer of Montalto Uffugo test field, show that there are no significant differences between the scaling laws considered and highlight the need to reduce the measurement uncertainties, which weigh heavily on the reliability of scaling laws.   Keywords: Scaling law; Hydraulic conductivity; Effective porosity; Laboratory measurement, Field measurement.   INFLUENCIA DE LA AMPLITUD DEL INTERVALO DE ESCALA EN LA DETERMINACIÓN DE LA CONDUCTIVIDAD HIDRÁULICA Y LA POROSIDAD EFECTIVA. EL CASO DE UN ACUÍFERO POROSA DEL SUR DE ITALIA   La importancia de una ley que, para un dado medio poroso, describa la variabilidad de la conductividad hidráulica en función de la porosidad efectiva es bien conocida. Frecuentemente esta variabilidad está representada por una ley de potencia a diferentes escalas, especialmente las de laboratorio y de campo. A menudo es útil tener una ley de escalamiento válida para un cierto rango de escala incluyendo los de laboratorio y campo. Por esta razón, es oportuno investigar la confiabilidad de las leyes que representan este comportamiento de escalamiento en los diferentes intervalos a los cuales típicamente se hace referencia. El propósito de este estudio es proporcionar evidencia sobre la confiabilidad de las leyes de escalamiento para intervalos de escala válidos para laboratorio, campo y globales (laboratorio + campo), verificando la consistencia con la proporcionalidad esperada entre la conductividad hidráulica y la porosidad efectiva para cada uno de estos. Esta verificación se llevó a cabo utilizando leyes de escalamiento de potencia para dos y cuatro parámetros respectivamente, y tratando de reducir las inevitables incertidumbres de medición. Los resultados experimentales obtenidos con referencia al acuífero confinado del campo de prueba Montalto Uffugo, muestran que no hay diferencias significativas entre las leyes de escalamiento consideradas y se destaca la necesidad de reducir las incertidumbres de medición, las cuales tienen un alto peso sobre la fiabilidad de las leyes de escala.   Palabras clave: ley de escalamiento; Conductividad hidráulica; porosidad efectiva; mediciones de laboratorio, medición de campo. &nbsp

Smoothing of Slug Tests for Laboratory Scale Aquifer Assessment—A Comparison Among Different Porous Media

A filtering analysis of hydraulic head data deduced from slug tests injected in a confined aquifer with different porous media is proposed. Experimental laboratory tests were conducted in a large-scale physical model developed at the University of Calabria. The hydraulic head data were deduced from the records of a pressure sensor arranged in the injection well and subjected to a processing operation to filter the high-frequency noise. The involved smoothing techniques are the Fourier transform and two types of wavelet transform. The performances of the filtered hydraulic heads were examined for different slug volumes and four model layouts in terms of optimal fitting of the Cooper’s analytical solution. The hydraulic head variations in the confined aquifer were analyzed using wavelet transform in order to discover their energy contributions and frequency oscillations. Finally, the raw and smoothed hydraulic heads were adopted to calculate the hydraulic conductivity of the aquifer

Variabilidad Espacial de Dimensiones Fractales en Curvas de Retención de Agua

The study of spatial variability of specific quantities characterizing the unsaturated soil is very important for the evaluation of polluting phenomena. Geostatistics is a useful tool for estimating the spatial variability of the considered parameters. The aim of this study is to improve the understanding of the spatial variability of the fractal dimension of water retention curves, showing the behaviour of this parameter in the site examined and particularly at the points where measures were not performed. The assessment of the fractal dimension was calculated by the analysis of scaling obtained from some fractal models and a comparison among the correspondent results was performed.El estudio de la variabilidad espacial de específicas magnitudes que caracterizan el suelo no saturado es muy importante para la evaluación de los fenómenos de contaminación. La Geoestadística es una herramienta útil para la estimación de la variabilidad espacial de los parámetros considerados. El objetivo de este estudio es mejorara la comprensión de la variabilidad espacial de la dimensión fractal en las curvas de retención de agua, mostrando de esta manera el comportamiento de este parámetro en los puntos muestreados y de manera particular en los puntos donde no existen muestras. La evaluación de la dimensión fractal se calculó por el análisis de escalamiento obtenido a partir de algunos modelos fractales y la posterior comparación entre los resultados correspondientes

Scaling behaviour of braided active channels: a Taylor’s power law approach

none9At a channel (reach) scale, braided channels are fluvial, geomorphological, complex systems that are characterized by a shift of bars during flood events. In such events water flows are channeled in multiple and mobile channels across a gravel floodplain that remain in unmodified conditions. From a geometrical point of view, braided patterns of the active hydraulic channels are characterized by multicursal nature with structures that are spatially developed by either simple- and multi-scaling behavior. Since current studies do not take into account a general procedure concerning scale measurements, the latter behavior is still not well understood. The aim of our investigation is to analyze directly, through a general procedure, the scaling behavior of hydraulically active channels per transect and per reach analyzed. Our generalized stochastic approach is based on Taylor’s law, and the theory of exponential dispersion distributions. In particular, we make use of a power law, based on the variance and mean of the active channel fluctuations. In this way we demonstrate that the number of such fluctuations with respect to the unicursal behavior of the braided rivers, follows a jump-process of Poisson and compound Poisson–Gamma distributions. Furthermore, a correlation is also provided between the scaling fractal exponents obtained by Taylor’s law and the Hurst exponents.Samuele De Bartolo, Stefano Rizzello, Ennio Ferrari, Ferdinando Frega, Gaetano Napoli, Raffaele Vitolo, Michele Scaraggi, Carmine Fallico, Gerardo SeverinoDE BARTOLO, Samuele; Rizzello, Stefano; Ferrari, Ennio; Frega, Ferdinando; Napoli, Gaetano; Vitolo, Raffaele; Scaraggi, Michele; Fallico, Carmine; Severino, Gerard

Determinación de los parámetros hidrodispersivos de una falda acuífera mediante pruebas con trazadores

Durante los últimos años se ha creado una conciencia mundial sobre los riesgos a la salud humana y al medio ambiente, producidos por la contaminación de los acuíferos. En este sentido, las acciones de remediación constituyen un elemento de fuerte interés tanto de un punto de vista científico como ingenierístico, cuyo objetivo fundamental es aquel de reconducir a condiciones seguras los niveles de concentración de los contaminantes encontrados en acuíferos. Sin embargo, antes de proceder a las acciones de remediación en sí, se vuelve fundamental una caracterización lo más precisa posible de este medio poroso, tanto desde el punto de vista hidrodinámico como hidrodispersivo. Los costos tanto económicos como humanos de una caracterización del acuífero in situ muchas veces son insostenibles, por tal motivo, la reproducción en laboratorio de un modelo de acuífero puede ser útil para efectuar un primer nivel de caracterización. Este artículo tiene como finalidad mostrar los resultados obtenidos de los principales parámetros hidrodispersivos de un acuífero freático artificial, reproducido mediante un prototipo de laboratorio, con el objeto de caracterizar el transporte de masa. El estudio se basa en estudios obtenidos de una precedente caracterización hidrodinámica del acuífero en mención. En este estudio se reportan los resultados obtenidos, en el modelo de acuífero, del coeficiente de dispersión y de la dispersividad longitudinal, a través de pruebas de trazabilidad, efectuadas en el prototipo

Determinación de los parámetros hidrodispersivos de una falda acuífera mediante pruebas con trazadores

During last years the global awareness about human-health and environment risks, caused by aquifers pollution, has grown. In this context, remediation actions on contaminated groundwater has acquired large importance from both scientific and engineering viewpoint whose main aim is the restoration of health-safety values of contaminants in groundwater for human beings. Before to start any remediation action, it is essential to characterize as accurate as possible of the porous medium properties, from both the hydrodispersive and hydrodynamic point of view. Often in situ aquifers characterization requires high economic and human costs and therefore laboratory tests and modelling are usually employed for a first level of characterization. The major aim of this work is to present the results of the main hydrodispersive parameters of a phreatic aquifer artificially reproduced by a laboratory prototype in order to characterize the mass transport within the considered system. Dispersion coefficient and longitudinal dispersivity presented are obtained as a result of a series of tracer tests carried out on the model which allow to complete the hydrodynamic characterization of the reproduced aquifer.Durante los últimos años se ha creado una conciencia mundial sobre los riesgos a la salud humana y al medio ambiente, producidos por la contaminación de los acuíferos. En este sentido, las acciones de remediación constituyen un elemento de fuerte interés tanto de un punto de vista científico como ingenierístico, cuyo objetivo fundamental es aquel de reconducir a condiciones seguras los niveles de concentración de los contaminantes encontrados en acuíferos. Sin embargo, antes de proceder a las acciones de remediación en sí, se vuelve fundamental una caracterización lo más precisa posible de este medio poroso, tanto desde el punto de vista hidrodinámico como hidrodispersivo. Los costos tanto económicos como humanos de una caracterización del acuífero in situ muchas veces son insostenibles, por tal motivo, la reproducción en laboratorio de un modelo de acuífero puede ser útil para efectuar un primer nivel de caracterización. Este artículo tiene como finalidad mostrar los resultados obtenidos de los principales parámetros hidrodispersivos de un acuífero freático artificial, reproducido mediante un prototipo de laboratorio, con el objeto de caracterizar el transporte de masa. El estudio se basa en estudios obtenidos de una precedente caracterización hidrodinámica del acuífero en mención. En este estudio se reportan los resultados obtenidos, en el modelo de acuífero, del coeficiente de dispersión y de la dispersividad longitudinal, a través de pruebas de trazabilidad, efectuadas en el prototipo