Evaluation of distributed recharge in an upland semi-arid karst system: the West Bank Mountain Aquifer,Middle East   总被引：2，自引：0，他引：2  

A. G. Hughes  M. M. Mansour  N. S. Robins 《Hydrogeology Journal》2008,16(5):845-854

Assessment of recharge in a structurally complex upland karst limestone aquifer situated in a semi-arid environment is difficult. Resort to surrogate indicators such as measurement of spring outflow and borehole discharge, is a common alternative, and attempts to apply conventional soil moisture deficit analysis may not adequately account for the intermittent spate conditions that arise in such environments. A modelling approach has been made using the West Bank Mountain Aquifer system in the Middle East as a trial. The model uses object oriented software which allows various objects to be switched on and off. Each of the main recharge processes identified in the West Bank is incorporated. The model allows either conventional soil moisture deficit analysis calculations or wetting threshold calculations to be made as appropriate, and accommodates both direct recharge and secondary recharge. Daily time steps enable recharge and runoff routing to be calculated for each node. Model runs have enabled a series of simulations for each of the three aquifer basins in the West Bank and for the whole of the West Bank. These provide recharge estimates comparable to those prepared by earlier workers by conventional means. The model is adaptable and has been successfully used in other environments.  相似文献   

Artificial neural network and liquefaction susceptibility assessment: a case study using the 2001 Bhuj earthquake data,Gujarat, India   总被引：2，自引：0，他引：2  

D. Ramakrishnan  T. N. Singh  N. Purwar  K. S. Barde  Akshay. Gulati  S. Gupta 《Computational Geosciences》2008,12(4):491-501

This study pertains to prediction of liquefaction susceptibility of unconsolidated sediments using artificial neural network (ANN) as a prediction model. The backpropagation neural network was trained, tested, and validated with 23 datasets comprising parameters such as cyclic resistance ratio (CRR), cyclic stress ratio (CSR), liquefaction severity index (LSI), and liquefaction sensitivity index (LSeI). The network was also trained to predict the CRR values from LSI, LSeI, and CSR values. The predicted results were comparable with the field data on CRR and liquefaction severity. Thus, this study indicates the potentiality of the ANN technique in mapping the liquefaction susceptibility of the area.  相似文献   

Hydrogeochemistry and isotope analyses used to determine groundwater recharge and flow in low-gradient catchments of the province of Buenos Aires,Argentina   总被引：7，自引：3，他引：4  

O. M. Quiroz Londoño  D. E. Martínez  C. Dapeña  H. Massone 《Hydrogeology Journal》2008,16(6):1113-1127

The region known as Pampa Plain, in Argentina, is a vast area characterized by slopes of less than 0.05%. The surface sediment is silty sand, mainly Aeolian, referred to as Pampean Loess, which is a phreatic aquifer unit of utmost importance for the water supply of the region. On account of the slight gradient, hydrogeological analyses using only hydraulic measurements are difficult to perform, often leading to confusing results. Thus, the study presented relies on hydrochemical modeling and isotopic determinations as well. The study area comprises three catchments in the inter-mountainous area corresponding to El Moro, Tamangueyú and Seco creeks, and covering 2,570 km² in the province of Buenos Aires. Measurements of piezometric levels and samples of groundwater, surface water and rainwater were carried out between January and March 2005. Major ion results were analyzed by means of hydrochemical graphs and hydrogeochemical modelling using NETPATH. The resulting data show that it is possible to identify local changes in recharge, flow direction and stream/groundwater relationship by using hydrochemical and isotopic information, which may become a useful and more precise tool for the study of particularly flat landscapes.  相似文献   

The Meso-Cenozoic thermo-tectonic evolution of the Eastern Pyrenees: an <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar fission track and (U–Th)/He thermochronological study of the Canigou and Mont-Louis massifs     

O. Maurel  P. Moniè  R. Pik  N. Arnaud  M. Brunel  M. Jolivet 《International Journal of Earth Sciences》2008,97(3):565-584

Vertical displacements on the SW–NE Têt fault (Eastern Pyrenees Axial Zone, France), which separates the Variscan Canigou-Carança and Mont-Louis massifs, were constrained using a thermochronologic multi-method approach. ⁴⁰Ar/³⁹Ar data from the granitic Mont-Louis massif record its Variscan cooling history and reveal no ages younger than Early Cretaceous, while the Canigou-Carança gneiss massif records systematically younger ⁴⁰Ar/³⁹Ar ages. These younger ⁴⁰Ar/³⁹Ar ages in the Canigou-Carança gneiss massif are the result of partial to total rejuvenation of argon isotopic systems related to a thermal flow coeval with the Cretaceous HT-BP metamorphism in the North Pyrenean Zone. Only the deepest rocks from the Canigou-Carança suffered this extensive Mid-Cretaceous thermal overprint probably due to differential burial around 4 km at that time. The post Mid-Cretaceous vertical displacements along the Têt fault are recorded by “low” temperature thermochronology using K-feldspar ⁴⁰Ar/³⁹Ar, zircon and apatite fission track and (U–Th)/He datings. The Mont-Louis granite samples experienced a long period of protracted cooling reflecting a lack of thermo-tectonic activity in this area from Late Palaeozoic to Early Cenozoic, followed by cooling from 55–60 Ma to Late Eocene at a mean rate of 15–20°C/Ma in the final stage. This cooling stage corresponds to Têt fault reactivation with a reversed component, promoting exhumation of the Mont-Louis roof zone contemporaneously with the south-vergent Pyrenean thrusting. In the Canigou-Carança massif, the main cooling event occurred from 32 to 18 Ma at a maximum rate of 30°C/Ma during Early Oligocene followed by a more moderate rate of 3°C/Ma from Late Oligocene to Early Burdigalian, coeval with the normal reactivation of the Têt fault in brittle conditions that accommodated the final exhumation of the massif during the opening of the Gulf of Lion.  相似文献   

Geochemistry of amphibolitized eclogites and cross-cutting tonalitic–trondhjemitic dykes in the Metamorphic Kimi Complex in East Rhodope (N.E. Greece): implications for partial melting at the base of a thickened crust     

I. Baziotis  E. Mposkos  V. Perdikatsis 《International Journal of Earth Sciences》2008,97(3):459-477

In the ultra-high pressure Metamorphic Kimi Complex widespread tonalitic–trondhjemitic dykes, with an intrusion age ca. 65–63 Ma, cross-cut boudins and layers of amphibolitized eclogites. Geochemical investigation proclaims the tied genetic relationship of the amphibolitized eclogites and the associated tonalitic–trondhjemitic dykes. The major and trace element contents and rare earth element patterns of the amphibolitized eclogites indicate formation of their protoliths by fractional crystallization of tholeiitic magmas in a back-arc environment. The tonalites and trondhjemites are characterized by moderate to high Sr contents (>130 ppm), and low Y (<8.2 ppm) and heavy rare earth element contents (Yb content of 0.19–0.88 ppm). The chemical composition of the tonalitic and trondhjemitic dykes are best explained by partial melting of a tholeiitic source like the amphibolitized eclogites with residual garnet and amphibole, at the base of a thickened crust during Early Tertiary subduction/accretion at the southern margins of the European continent.  相似文献   

Surface water–groundwater interaction and chemistry in a mineral-armored hydrothermal outflow channel, Yellowstone National Park, USA     

M. V. Vitale  P. Gardner  N. W. Hinman 《Hydrogeology Journal》2008,16(7):1381-1393

Small quantities of groundwater interact with hydrothermal surface water to drive in-stream geochemical processes in a silica-armored hot-spring outflow channel in Yellowstone National Park, USA. The objective of this study was to characterize the hydrology and geochemistry of this unique system in order to (1) learn more about the Yellowstone Plateau’s subsurface water mixing between meteoric and hydrothermal waters and (2) learn more about the chemical and physical processes that lead to accumulation of streambed cements, i.e., streambed armor. A combination of hydrological, geochemical, mineralogical, microscopic, and petrographic techniques were used to identify groundwater and surface-water exchange. Interaction could be identified in winter because of differences in surface water and groundwater composition but interaction at other times of the year cannot be ruled out. Dissolved constituents originating from groundwater (e.g., Fe(II) and Mg) were traced downstream until oxidation and/or subsequent precipitation with silica removed them, particularly where high affinity substrates like cyanobacterial surfaces were present. Because the stream lies in a relatively flat drainage basin and is fed mainly by a seasonally relatively stable hot spring, this system allowed study of the chemical processes along a stream without the obscuring effects of sedimentation.  相似文献   

Comment on “Spherical harmonic analysis of Earth’s conductive heat flow” by V. M. Hamza, R. R. Cardoso and C. F. Ponte Neto     

Henry N. Pollack  David S. Chapman 《International Journal of Earth Sciences》2008,97(2):227-231

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New data on the present-day active fluid regime of fractured zones of crystalline basement and sedimentary cover in the eastern part of Volga-Ural region     

Irina N. Plotnikova 《International Journal of Earth Sciences》2008,97(5):1131-1142

The study area is the South Tatarstan Arch located in the Volgo-Ural Region, which is an enigmatic crustal segment occupying one third of the East European Platform. Monitoring studies have shown that fluid discharge processes are still active and time-dependent. This paper presents an integrated review of the geological, geophysical, hydrochemical and geochemical studies of the crystalline basement of Tatarstan. These studies are based on the stratigraphic and compositional schemes within the crystalline basement, the drilling of deep wells, the geodynamic activity of the fractured zones of the crystalline basement and the presence of fluids therein. Furthermore, the changes in the chemical composition of the basement waters are taken into account.  相似文献   

Environmental Factors Contributing to the Development and Demise of a Toxic Dinoflagellate (<Emphasis Type="Italic">Karlodinium veneficum</Emphasis>) Bloom in a Shallow,Eutrophic, Lagoonal Estuary     

Nathan S. Hall  R. Wayne Litaker  Elizabeth Fensin  Jason E. Adolf  Holly A. Bowers  Allen R. Place  Hans W. Paerl 《Estuaries and Coasts》2008,31(2):402-418

A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes, coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter). By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary.  相似文献   

A Numerical Simulation of Residual Circulation in Tampa Bay. Part II: Lagrangian Residence Time   总被引：1，自引：0，他引：1  

Steven D. Meyers  Mark E. Luther 《Estuaries and Coasts》2008,31(5):815-827

Lagrangian retention and flushing are examined by advecting neutrally buoyant point particles within a circulation field generated by a numerical ocean model of Tampa Bay. Large temporal variations in Lagrangian residence time are found under realistic changes in boundary conditions. Two 90-day time periods are examined. The first (P1) is characterized by low freshwater inflow and weak baroclinic circulation. The second (P2) has high freshwater inflow and strong baroclinic circulation. At the beginning of both time periods, 686,400 particles are released uniformly throughout the bay. Issues relating to particle distribution and flushing are examined at three different spatial scales: (1) at the scale of the entire bay, (2) the four major regions within the bay, and (3) at the scale of individual model grid cells. Two simple theoretical models for the particle number over time, N(t), are fit to the particle counts from the ocean model. The theoretical models are shown to represent N(t) reasonably well when considering the entire bay, allowing for straightforward calculation of baywide residence times: 156 days for P1 and 36 days for P2. However, the accuracy of these simple models decreases with decreasing spatial scale. This is likely due to the fact that particles may exit, reenter, or redistribute from one region to another in any sequence. The smaller the domain under consideration, the more this exchange process dominates. Therefore, definitions of residence time need to be modified for “non-local” situations. After choosing a reasonable definition, and removal of the tidal and synoptic signals, the residence times at each grid cell in P1 is found to vary spatially from a few days to 90 days, the limit of the calculation, with an average residence time of 53 days. For P2, the overall spatial pattern is more homogeneous, and the residence times have an average value of 26 days.  相似文献