Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Conceptual models for karstic aquifers
White, W.B.
Speleogenesis and Evolution of Karst Aquifers , 2003,
Abstract: Karstic carbonate aquifers are extremely heterogeneous with a distribution of permeability that spans many orders of magnitude. They often contain open conduit flow paths with hydraulic characteristics more like surface streams than ground water. Karstic carbonate aquifers have highly efficient interfaces with surface water through swallets and springs. Characterizing parameters include: area of ground-water basin, area of allogenic recharge basins, conduit carrying capacity, matrix hydraulic conductivity, fracture hydraulic conductivity, conduit system response time, and conduit/fracture coupling coefficients. The geologic setting provides boundary conditions that allow the generalized conceptual model to be applied to specific aquifers.
Action COST 621 Groundwater management of coastal karstic aquifers
Metka Petri?,Janja Kogov?ek,Janko Urbanc
Geologija , 2002,
Abstract: COST 621 Groundwater management of coastal karstic aquifers” is an international project in the frame of the European Union in which 12 European countries, including Slovenia, took an active part in the years 1997-2002. The main objective of the Action is to increase the knowledge necessary to establish criteria for improving groundwaterresource utilisation in karstic coastal aquifers and for recovering groundwater resource in aquifers over-exploited and salinised due to sea water intrusion. Based on gathered results “Guidelines for the groundwater management of coastal karstic aquifers” were compiled and will be published as a special booklet. In this way the dissemination of the results will be provided.
Comparative estimate of resistance to drought fro selected karstic aquifers in Bulgaria  [PDF]
Orehova Tatiana
International Journal of Speleology , 2004,
Abstract: Effective management of water resources requires adequate knowledge of groundwater system including the influence of climate variability and climate change. The drought of 1982-1994 in Bulgaria has led to important decrease of springflow and lowering of water levels. Therefore, groundwater demonstrated its vulnerability to drought. The purpose of this paper is to determine relative resistance of selected aquifers in Bulgaria to a prolonged decrease of recharge to groundwater. The drought resistance indicator has been defined for some karstic aquifers based on the method proposed in report of BRGM. The data from National Hydrogeological Network located in the National Institute of Meteorology and Hydrology were processed. For the aim of this study, time-series of discharge for karstic springs were used. Stations with significant impact of human activity on groundwater were eliminated. The results show that most of studied aquifers in Bulgaria have moderate and weak resistance to the drought. They are vulnerable to droughts and need good management for effective use of groundwater resources.
Interaction between karstic aquifers and allogenic rivers: The aquifer of the national park of the ephemeral river Lobos Canyon (Spain)  [PDF]
Eugenio Sanz Pérez, Ignacio Menéndez Pidal, Rafael Segovia Rosales
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.52A042

A methodology is described for understanding the interaction of karstic aquifers with allogenic rivers, where little information is available. This methodology includes conventional hydrogenology methods tracer tests and measurements of flow into, out of and circulating within the karstic system. The method is designed to understand the hydrogeological behaviour of a river in sufficient detail, given a short study period. The methodology is applied to a karstic system in Spain, obtaining useful, quantitative results for a hydrological year, such as an estimate of the water balance, differentiation between autogenic and allogenic natural recharge, relationship and connection between the river and the aquifer, and measurements of infiltration capacity in watercourses under different hydrological situations. The paper deals with a useful example that could be applied to other rivers and aquifers where few data are available. It can be applied to aquifers under a natural regime and Mediterranean climate.

Numerical Simulation of Pollutant Transport in Fractured Vuggy Porous Karstic Aquifers
Xiaolin Fan,Shuyu Sun,Wei Wei,Jisheng Kou
Journal of Applied Mathematics , 2011, DOI: 10.1155/2011/498098
Abstract: This paper begins with presenting a mathematical model for contaminant transport in the fractured vuggy porous media of a species of contaminant (PCP). Two phases are numerically simulated for a process of contaminant and clean water infiltrated in the fractured vuggy porous media by coupling mixed finite element (MFE) method and finite volume method (FVM), both of which are locally conservative, to approximate the model. A hybrid mixed finite element (HMFE) method is applied to approximate the velocity field for the model. The convection and diffusion terms are approached by FVM and the standard MFE, respectively. The pressure distribution and temporary evolution of the concentration profiles are obtained for two phases. The average effluent concentration on the outflow boundary is obtained at different time and shows some different features from the matrix porous media. The temporal multiscale phenomena of the effluent concentration on the outlet are observed. The results show how the different distribution of the vugs and the fractures impacts on the contaminant transport and the effluent concentration on the outlet. This paper sheds light on certain features of karstic groundwater are obtained.
Measurement of radon concentrations at Super-Kamiokande  [PDF]
Super-Kamiokade Collaboration,:,Y. Takeuchi et al
Physics , 1999, DOI: 10.1016/S0370-2693(99)00311-1
Abstract: Radioactivity from radon is a major background for observing solar neutrinos at Super-Kamiokande. In this paper, we describe the measurement of radon concentrations at Super-Kamiokande, the method of radon reduction, and the radon monitoring system. The measurement shows that the current low-energy event rate between 5.0 MeV and 6.5 MeV implies a radon concentration in the Super-Kamiokande water of less than 1.4 mBq/m$^3$.
Radon concentrations in soil of the city of Podgorica, Montenegro
P. Vukotich,V. V. Uvarov,N. Antovich,S. Dapchevich
Geofísica internacional , 2002,
Abstract: Radon concentrations in soil of the city of Podgorica, capital of Montenegro, were measured using passive radiometers. The radiometers were placed in the soil at a depth of 70-80 cm, in refilled holes, and cellulose nitrate detectors were exposed during 14 days. The arithmetic mean of the radon concentrations at 67 locations is found to be 37 kBq/m3, with a standard deviation of 16 kBq/m3. The frequency distribution of radon levels in soil is almost symmetrical. This investigation shows that the radon level in soil above the geological fault, in a non-seismic situation, is not higher than in soil of other city areas. The radon concentrations in soil at a contact zone between flat terrain and rocky hills are not found to be generally higher than elsewhere in the city area.
Indoor radon concentrations above bauxite ground
Antovich, N.,V. V. Uvarov,P. Vukotich,S. Dapchevich
Geofísica internacional , 2002,
Abstract: Uranium content in bauxite is generally several times higher than its average occurrence in the Earth’s crust. Bauxite deposits in Montenegro are widespread in the Niksich region. Some settlements are built above these deposits, and some detached family houses have basements directly in bauxite ground. Indoor radon measurements in this region were performed in such places, and in places where there is no presence of bauxite. Radon was measured on the ground floor, using cellulose nitrate detectors exposed 3 months during the winter season. The results show that bauxite ground produces a high indoor radon level. However, all measured concentrations are below the tolerance of 400 Bq/m3 adopted in Yugoslavia, except in two houses built directly on bauxite ground, where indoor radon concentration reached 540 Bq/m3 and 676 Bq/m3.
The influence of geology on elevated radon concentrations in Slovenian schools and kindergartens
Andreja Popit,Janja Vaupoti?
Geologija , 2002,
Abstract: 76 instantaneous indoor radon concentrations above the Slovenian action level of 400 Bqm-3 were selected from the database of 1600 radon concentrations in kindergartens and schools, assembled during the Slovenian National Radon Programme. A relationship wasfound between indoor radon concentrations, and geology of rocks under the foundations (uranium content, permeability, porosity, tectonic fractures) and the quality of building construction.
Influence of variable stress on underground radon concentrations
A. Kies,F. Massen,Z. Tosheva
Geofísica internacional , 2002,
Abstract: Stresses applied to rocks of the Earth’s crust cause local deformation of the crust. In order to monitor a radon signal due to variable pressures and rock stresses we use a natural laboratory under a reservoir of the Vianden (Luxembourg) pumping storage power plant. Depending on energy demands, the artificial reservoirs at the top of a hill experience daily variations in water levels of up to 16 meters, thus exerting variable pressures on the underlying rocks.Radon concentrations are continuously measured in boreholes drilled into the bedrock under water reservoir. We observe some very strong variations in transient radon concentrations induced by variations of water level. The reservoir consists of two independent reservoirs that were emptied individually for some period of time. The observed radon pattern depends on the location of the boreholes under the reservoir and is different if both basins are working together, or if one of the reservoirs is empty. The observed patterns can be accounted for by variable pathways of fluids, fluid overpressure and a dynamic flow in cracks.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.