A modified multiple tension upward infiltration method to estimate the soil hydraulic properties          下载免费PDF全文

D. Moret‐Fernández  B. Latorre  C. Peña‐Sancho  T.A. Ghezzehei 《水文研究》2016,30(17):2991-3003

Determination of saturated hydraulic conductivity, K_s, and the shape parameters α and n of the water retention curve, θ(h), is of paramount importance to characterize the water flow in the vadose zone. This work presents a modified upward infiltration method to estimate K_s, α and n from numerical inverse analysis of the measured cumulative upward infiltration (CUI) at multiple constant tension lower boundary conditions. Using the HYDRUS‐2D software, a theoretical analysis on a synthetic loam soil under different soil tensions (0, 0–10, 0–50 and 0–100 cm), with and without an overpressure step of 10 cm high from the top boundary condition at the end of the upward infiltration process, was performed to check the uniqueness and the accuracy of the solutions. Using a tension sorptivimeter device, the method was validated in a laboratory experiment on five different soils: a coarse and a fine sand, and a 1‐mm sieved loam, clay loam and silt‐gypseous soils. The estimated α and n parameters were compared to the corresponding values measured with the TDR‐pressure cell method. The theoretical analysis demonstrates that K_s and θ(h) can be simultaneously estimated from measured upward cumulative infiltration when high (>50 cm) soil tensions are initially applied at the lower boundary. Alternatively, satisfactory results can be also obtained when medium tensions (<50 cm) and the K_s calculated from the overpressure step at the end of the experiment are considered. A consistent relationship was found between the α (R² = 0.86, p < 0.02) and n (R² = 0.97, p < 0.001) values measured with the TDR‐pressure cell and the corresponding values estimated with the tension sorptivimeter. The error between the α (in logarithm scale) and n values estimated with the inverse analysis and the corresponding values measured with pressure chamber were 3.1 and 6.1%, respectively. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The impact of man-made hydrology on the lower stream bed of the Salado River drainage basin (Argentina)   总被引：2，自引：0，他引：2  

V. Conzonno  P. Miretzky  A. Fernández Cirelli 《Environmental Geology》2001,40(8):968-972

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Ellipsoidal density models and hydrostatic equilibrium: Interim report     

A. Marussi  H. Moritz  R.H. Rapp  R.O. Vicente 《Physics of the Earth and Planetary Interiors》1974,9(1):4-6

From the point of view of consistency with the Geodetic Reference System 1967, it would be desirable that the boundary surface of a Standard Earth Model is an exact equipotential ellipsoid. This is incompatible with the requirement that it be a figure of hydrostatic equilibrium. The report investigates the relation between equipotential ellipsoids and equilibrium figures. The principal conclusion is that it is possible to find an ellipsoidal model that has the same distribution of density and flattening (more precisely, of the parameter f′ as defined in the paper) as a hydrostatic model, the deviations being only of second order in the flattening.  相似文献   

Evaluation of groundwater availability and sustainable extraction rate for the Upper Santiago Valley Aquifer,Chile   总被引：1，自引：0，他引：1  

José?F.?Mu?ozEmail author  Bonifacio?Fernández  Cristián?Escauriaza 《Hydrogeology Journal》2003,11(6):687-700

The use of groundwater as water supply has increased dramatically in Santiago, Chile, during the last decades, and there is a need for accurately estimating the actual groundwater supply capacity in the upper Santiago Valley aquifer. The behavior of this aquifer was studied in order to determine the availability of water and the long-range sustainable extraction rate.Water-table depths were simulated using a numerical model with information on recharge from the last 48 years under different extraction policies. With this series of groundwater level data, groundwater level probability distribution functions were determined and extraction statistics were estimated by fitting time series models and by using the crossing theory. With this information, it has been possible to calculate the risk of being unable to supply groundwater demand because the results verify that only 67% of the water rights granted are able to be extracted on a sustained basis with a 90% exceedance probability. Furthermore, the results obtained demonstrate that the method is adequate for determining exceedance probabilities of groundwater flow.

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Resumen El uso de las aguas subterráneas como fuente de abastecimiento se ha incrementado enormemente en Santiago de Chile durante las últimas décadas, por lo que se necesita estimar de forma adecuada la capacidad actual de suministro del acuífero superior del Valle de Santiago. Se ha estudiado el comportamiento de este acuífero para determinar la disponibilidad de recursos y la tasa de extracción sustentable a largo plazo.Se ha simulado los niveles freáticos del acuífero utilizando un modelo numérico con información de la recarga en los últimos 48 años bajo diferentes regímenes de extracción. Con esta serie de datos de los niveles en el acuífero, se ha determinado la distribución de probabilidad de los niveles de las aguas subterráneas y se ha estimado las estadísticas de las extracciones mediante el ajuste de modelos de series temporales y la teoría de cruce. Con esta información, se ha podido calcular el riego de no satisfacer la demanda de abastecimiento, puesto que los resultados verifican que sólo se podría extraer el 67% de las concesiones de agua existentes de manera sustentable con un 90% de probabilidad de excedencia. Aún más, los resultados obtenidos demuestran que el método es adecuado para determinar las probabilidades de excedencia del flujo de las aguas subterráneas.

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Resumé Lutilisation de leau souterraine pour leau potable sest considérablement accrue à Santiago (Chili) au cours des derniers lustres; cest pourquoi il est maintenant nécessaire destimer avec précision la capacité réelle dalimentation de la nappe de laquifère supérieur de la vallée de Santiago. Le fonctionnement de cet aquifère a été étudié afin de déterminer la disponibilité en eau et le taux dextraction durable à long terme.Les niveaux de la nappe ont été simulés avec un modèle numérique à partir dinformation sur la recharge au cours des 48 dernières années pour différentes politiques dextraction. A partir de cette série de données piézométriques, des fonctions de distribution de probabilité des niveaux de la nappe ont été déterminées et des statistiques dextraction ont été estimées par ajustement de modèles de séries chronologiques en utilisant la théorie du croisement. Avec ces informations, il a été possible de calculer le risque de ne pas pouvoir satisfaire la demande deau souterraine, puisque les résultats vérifient que seulement 67% des droits deau attribués peuvent être extraits sur une base durable avec une probabilité de dépassement de 90%. En outre, les résultats obtenus démontrent que la méthode est adaptée à la détermination des probabilités de dépassement de lécoulement souterrain.

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Flood Response to Solar Activity in the Tagus Basin (Central Spain) over the Last Millennium     

Gerardo Benito  Andrés Díez-Herrero  María Fernández de Villalta 《Climatic change》2004,66(1-2):27-28

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Persistent organic pollutants in remote freshwater ecosystems   总被引：3，自引：0，他引：3  

Pilar Fernández  Guillem Carrera  Joan O. Grimalt 《Aquatic Sciences - Research Across Boundaries》2005,67(3):263-273

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DFT study of the cation arrangements in the octahedral and tetrahedral sheets of dioctahedral 2:1 phyllosilicates     

Alfonso Hernández-Laguna  Elizabeth Escamilla-Roa  Vicente Timón  Martin T. Dove  C. Ignacio Sainz-Díaz 《Physics and Chemistry of Minerals》2006,33(10):655-666

Quantum mechanical calculations based on the density functional theory (DFT) are used to study the crystal structures of dioctahedral 2:1 phyllosilicates. The isomorphous cation substitution is investigated by exploring different substitutions of octahedral Al³⁺ by Mg²⁺ or Fe³⁺, tetrahedral substitution of Si⁴⁺ by Al³⁺, and different interlayer cations (IC) (Na⁺, K⁺, Ca²⁺, and Mg²⁺). Samples with different kinds of layer charges are studied: only tetrahedrally charged, only octahedrally charged, or mixed octahedral/tetrahedral charged. The effect of the relative arrangements of these substitutions on the lattice parameters and total energy is studied. The experimental observation of segregation tendency of Fe³⁺ and dispersion tendency of Mg²⁺ in the octahedral sheet is reproduced and explained with reference to the relative energies of the octahedral cation arrangements. These energies are higher than those due to the IC/tetrahedral and IC/octahedral relative arrangements. The tetrahedral and octahedral substitutions that generate charged layers also tend to be dispersed. The octahedral cation exchange potentials change with the IC-charge/ionic radius value.  相似文献   

Origin and depositional environment of Ordovician stratiform iron mineralization from Zamora (NW Iberian Peninsula)     

A. Fernández  M. C. Moro 《Mineralium Deposita》1998,33(6):606-619

The Ordovician stratiform iron deposits at Zamora (NW Iberia) are arranged in several levels ranging between 0.2 and 1.5 m in thickness, which are interstratified in the upper member of the “Pielgo” Quartzites Formation (Arenig). The sandy nature, and trace-fossils corresponding to the ichnogenus Cruziana and Daedalus, together with major and trace element contents of this formation suggest an inter and subtidal, shallow marine depositional environment, which on a global scale formed part of a broad shelf situated in the northern margin of the Gondwana continent. The iron mineralization displays a foliated and banded structure due to the alternation of quartzitic, phosphatic (apatite), chamositic, chamositic-biotitic and ferriferous (magnetite and hematite) beds. They have high TiO₂, Ta, Sc, V, Nb, Co, Zn and Y contents. The magnetite contains unusually large amounts of TiO₂, V, Cr and Ni; there is also a clear depletion in Eu and the (Eu/Sm)_CN ratio is <1 and the (Sm/Yb)_CN ratio is >1. The chamosite contains high concentrations of Cr and V. These results suggest that iron was supplied from the weathering of a continental source, in combination with volcanic activity, such as within-basin basic volcanism or the presence of basic volcanic rocks in the exposed land. The physicochemical conditions of iron mineral crystallization calculated from chamosite compositions are the following: log f O₂: −38.8 to −30.7, log f S₂: −13.2 to −9.5 and T: 200 to 330 °C. These results together with the δ¹⁸O value (∼2‰) of the magnetite suggest that chamosite and magnetite were crystallized during later diagenesis and early low-grade metamorphism under redox conditions below the magnetite-hematite buffer. Received: 25 September 1996 / Accepted: 2 February 1998  相似文献   

Microdeformation of lacustrine laminite sequences from Late Miocene formations of SE Spain: an interpretation of loop bedding   总被引：2，自引：0，他引：2  

Jose P. Calvo  Miguel Rodriguez-Pascua  Silvia Martin-Velazquez  Sergio Jimenez  & Gerardo De Vicente 《Sedimentology》1998,45(2):279-292

Lacustrine laminated sediments (laminites) present in Late Miocene formations of the Híjar Basin, SE Spain, display well developed loop bedding, a structure consisting of bundles of laminae that are sharply constricted at intervals, giving a morphology of loops or links of a chain. The laminite sequences, which are interbedded with turbidite marlstones, were accumulated on the bottom of a permanently stratified lake developed in a rapidly subsiding basin limited by 010° and 105° normal faults. As deduced from both macro- and microdeformational analyses, the basin evolved under an extensional stress field throughout the Late Miocene. Four main types of loops, simple and complex loops with subcategories, have been recognized within the laminite sequence. Simple loops of type 1 show the best definite pattern, quite similar to ' pinch and swell structures ', a type of boudinage typical of stretching of alternating beds where the competence contrast is not strongly marked. The remaining loop types display contortion and occasional breakage of laminae (microfaulted edges) indicative of microdeformation near the boundary between the ductile-brittle deformational fields. The distribution of the various loop types across the laminite sequence reflects an interplay between progressive lithification of the laminites as sedimentation progressed and tectonic stresses which affected the sediment sequence. Accordingly, a mechanism of deformation under an extensional stress field, ultimately related to the creep movement of the main basin faults which resulted in successive seismic shocks of low magnitude, is proposed to explain the formation of loop bedding in the laminites.  相似文献   

Release of 222Rn from some soils     

C. Dueñas  M. C. Fernández  J. Carretero  E. Liger  M. Pérez 《Annales Geophysicae》1997,15(1):124-133

Measurements have been made of ²²²Rn release from diverse soils in the region surrounding Malaga, Spain. These flux measurements were carried out by two methods. A direct method using a static chamber technique and another indirect method obtained from concentration profile measurements of ²²²Rn in the soil air. The effects of meteorological variables and other parameters on ²²²Rn flux were studied. The factors that most affected the instantaneous value of ²²²Rn release were humidity and soil thermal gradient. The directly measured ²²²Rn fluxes at investigated sites are higher than ²²²Rn fluxes derived by the indirect method.  相似文献