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| 2. |
- Barthel, Roland, 1967
(författare)
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An indicator approach to assessing and predicting the quantitative state of groundwater bodies on the regional scale with a special focus on the impacts of climate change
- 2011
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 19:3, s. 525-546
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Tidskriftsartikel (refereegranskat)abstract
- An integrated approach for assessing the availability of groundwater under conditions of 'global-change' is presented. The approach is embedded in the DANUBIA system developed by the interdisciplinary GLOWA-Danube Project to simulate the interaction of natural and socio-economic processes within the Upper Danube Catchment (UDC, 77,000 km2 and located in parts of Germany, Austria, Switzerland and Italy). The approach enables the quantitative assessment of groundwater bodies (zones), which are delineated by intersecting surface watersheds, regional aquifers, and geomorphologic regions. The individual hydrogeological and geometrical characteristics of these zones are accounted for by defining characteristic response times and weights to describe the relative significance of changes in variables (recharge, groundwater level, groundwater discharge, river discharge) associated with different states. These changes, in each zone, are converted into indices (GroundwaterQuantityFlags). The motivation and particularities of regional-scale groundwater assessment and the background of GLOWA-Danube are described, along with a description of the developed methodology. The approach was applied to the UDC, where several different climate scenarios (2011-2060) were evaluated. A selection of results is presented to demonstrate the potential of the methodology. The approach was inspired by the European Water Framework Directive, yet it has a stronger focus on the evaluation of global-change impacts. © 2011 Springer-Verlag.
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| 3. |
- Bosson, Emma, et al.
(författare)
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Exchange and pathways of deep and shallow groundwater in different climate and permafrost conditions using the Forsmark site, Sweden, as an example catchment
- 2013
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Ingår i: Hydrogeology Journal. - : Springer Nature. - 1431-2174 .- 1435-0157. ; 21:1, s. 225-237
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Tidskriftsartikel (refereegranskat)abstract
- This study simulates and quantifies the exchange and the pathways of deep and shallow groundwater flow and solute transport under different climate and permafrost conditions, considering the example field case of the coastal Forsmark catchment in Sweden. A number of simulation scenarios for different climate and permafrost condition combinations have been performed with the three-dimensional groundwater flow and transport model MIKE SHE. Results show generally decreasing vertical groundwater flow with depth, and smaller vertical flow under permafrost conditions than under unfrozen conditions. Also the overall pattern of both the vertical and the horizontal groundwater flow, and the water exchange between the deep and shallow groundwater systems, change dramatically in the presence of permafrost relative to unfrozen conditions. However, although the vertical groundwater flow decreases significantly in the presence of permafrost, there is still an exchange of water between the unfrozen groundwater system below the permafrost and the shallow groundwater in the active layer, via taliks. ‘Through taliks’ tend to prevail in areas that constitute groundwater discharge zones under unfrozen conditions, which then mostly shift to net recharge zones (through taliks with net downward flow) under permafrost conditions.
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| 4. |
- Follin, Sven, et al.
(författare)
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A transmissivity model for deformation zones in fractured crystalline rock and its possible correlation to in situ stress at the proposed high-level nuclear waste repository site at Forsmark, Sweden
- 2014
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 22:2, s. 299-311
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Tidskriftsartikel (refereegranskat)abstract
- The Forsmark site was recently proposed by the Svensk Karnbranslehantering AB (SKB) to serve as the potential site for construction of a future geological repository for spent high-level nuclear fuel at about 470 m depth in fractured crystalline rock. The considerations included, among other things, distance from regionally significant deformation zones with highly strained rock, lithological homogeneity, low hydraulic conductivity, groundwater salinity with an acceptable range, and lack of potential mineral resources. This report describes the calculation of transmissivity of deduced deformation zones at Forsmark and the transmissivity model used in the regional groundwater flow modeling carried out in support of the integrated site description. Besides significant decrease with increasing depth (more than four orders of magnitude over a depth of about 1 km), the calculated transmissivity values also reveal considerable spatial variability along the strikes of the zones, i.e. lateral heterogeneity (more than two orders of magnitude). A hydro-mechanical coupling is discussed, based on presented models for the tectonic evolution and the principal stress tensor. Tentatively, laboratory-scale relationships developed from normal stress experiments on a single fracture in crystalline rock can be used to estimate the maximum values of transmissivity of deduced deformation zones at Forsmark.
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| 5. |
- Frampton, Andrew, et al.
(författare)
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Permafrost degradation and subsurface-flow changes caused by surface warming trends
- 2012
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 21:1, s. 271-280
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Tidskriftsartikel (refereegranskat)abstract
- Change dynamics of permafrost thaw, andassociated changes in subsurface flow and seepage into surface water, are analysed for different warming trends in soil temperature at the ground surface with a three-phase two-component flow system coupled to heat transport. Changes in annual, seasonal and extreme flows are analysed for three warming-temperature trends, representing simplified climate change scenarios. The results support previous studies of reduced temporal variability of groundwater flow across all investigated trends. Decreased intra-annual flow variability may thus serve asan early indicator of permafrost degradation before longer term changes in mean flows are notable. This is advantageous since hydrological data are considerably easier to obtain, may be available in longer time series, and generally reflect larger-scale conditions than direct permafrost observations. The results further show that permafrost degradation first leads to increasing water discharge, which then decreases as the permafrost degradation progresses further to total thaw. The most pronounced changes occur for minimum annual flows. The configuration considered represents subsurface discharge from a generic heterogeneous soil-type domain.
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| 6. |
- Jie, Z., et al.
(författare)
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Combination of soil-water balance models and water-table fluctuation methods for evaluation and improvement of groundwater recharge calculations
- 2011
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 19:8, s. 1487-1502
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Tidskriftsartikel (refereegranskat)abstract
- Despite a long history of related research, quantifying and verifying recharge is still a major challenge. The combination and comparison of conceptually different methods has been recommended as a strategy for evaluating recharge estimates. In this article, recharge estimates from water-table fluctuation (WTF) methods are combined with and compared to the results of the spatially and temporally discretized soil-water-balance model PROMET (processes of radiation, mass and energy transfer). As PROMET and WTF methods rely on different measurable variables, a comparison of these two contrasting techniques allows improved assessment of the plausibility of recharge estimates. An enhanced approach to WTF methods is presented. The approach assumes that in the case of no recharge, there exists a maximum possible potential decline for any given groundwater level. The primary conclusion is that WTF methods are excellent for determining the plausibility of spatially distributed regional-groundwater-recharge estimation approaches and for detecting inconsistencies in available models. Recharge estimates derived from WTF approaches alone are, however, not suitable for regional-scale recharge estimation due to (1) their strong dependency on local data, applicability of which is limited to only very specific conditions, and (2) their sensitivity to influences other than recharge.
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| 7. |
- Kumanova, X., et al.
(författare)
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Recharge and sustainability of a coastal aquifer in northern Albania
- 2014
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 22:4, s. 883-892
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Tidskriftsartikel (refereegranskat)abstract
- The River Mati in Albania has formed a coastal plain with Holocene and Pleistocene sediments. The outer portion of the plain is clay, with three underlying aquifers that are connected to an alluvial fan at the entry of the river into the plain. The aquifers supply water for 240,000 people. Close to the sea the aquifers are brackish. The brackish water is often artesian and found to be thousands of years old. Furthermore, the salinity, supported by delta O-18 results, does not seem to be due to mixing with old seawater but due to diffusion from intercalated clay layers. Heavy metals from mines in the upstream section of River Mati are not an immediate threat, as the pH buffering of the river water is good. Moreover, the heavy metals are predominantly found in suspended and colloidal phases. Two sulphur isotope signatures, one mirroring seawater sulphate in the brackish groundwater (delta S-34 > 21 aEuro degrees) and one showing the influence of sulphide in the river and the fresh groundwater (delta S-34 < 10 aEuro degrees), indicate that the groundwater in the largest well field is recharged from the river. The most serious threat is gravel extraction in the alluvial fan, decreasing the hydraulic head necessary for recharge and causing clogging of sediments.
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| 8. |
- Larsson, Martin, 1980-, et al.
(författare)
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Understanding the effect of single fracture heterogeneity from single well injection withdrawal (SWIW) tests
- 2013
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Ingår i: Hydrogeology Journal. - New York : Springer-Verlag New York. - 1431-2174 .- 1435-0157. ; 21:8, s. 1691-1700
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Tidskriftsartikel (refereegranskat)abstract
- The single well injection withdrawal (SWIW) tracer test on a fracture or fracture zone is a method used to estimate its tracer retardation properties. In this study, the effects of single fracture aperture heterogeneity on SWIW test tracer breakthrough curves are examined by numerical modelling. The effects of the matrix diffusion and sorption is accounted for by using a particle tracking method through the addition of a time delay added to the advective transport time. For a given diffusion and sorption property value (Pm) and for a heterogeneous fracture, the peak concentration is larger compared to a homogeneous fracture. The cumulative breakthrough curve for a heterogeneous fracture is similar to that for a homogeneous fracture and a less sorptive/diffusive tracer. It is demonstrated that the fracture area that meets the flowing water, the so-called specific flow-wetted surface (sFWS) of the fracture, can be determined by comparing the observed breakthrough curve for a heterogeneous fracture with that for a homogeneous fracture. SWIW tests are also simulated with a regional pressure gradient present. The results point to the possibility of distinguishing the effect of the regional pressure gradient from that of diffusion through the use of multiple tracers with different Pm-values.
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| 9. |
- Marklund, Lars, et al.
(författare)
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The use of spectral analysis-based exact solutions to characterize topography-controlled groundwater flow
- 2011
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 19:8, s. 1531-1543
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Tidskriftsartikel (refereegranskat)abstract
- Spectral analysis enhances the ability to analyze groundwater flow at a steady state by separating the top boundary condition into its periodic forms. Specifically, spectral analysis enables comparisons of the impact of individual spatial scales on the total flow field. New exact spectral solutions are presented for analyzing 3D groundwater flow with an arbitrarily shaped top boundary. These solutions account for depth-decaying, anisotropic and layered permeability while utilizing groundwater flux or the phreatic surface as a top boundary condition. Under certain conditions, groundwater flow is controlled by topography. In areas where the groundwater flow is controlled by the topography, the unknown water table is often approximated by the topography. This approximation induces a systematic error. Here, the optimal resolution of digital elevation models (DEMs) is assessed for use as a top boundary in groundwater flow models. According to the analysis, the water-table undulation is smoother than the topography; therefore, there is an upper limit to the resolution of DEMs that should be used to represent the groundwater surface. The ability to represent DEMs of various spectral solutions was compared and the results indicate that the fit is strongly dependent on the number of harmonics in the spectral solution.
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| 10. |
- Neretnieks, Ivars
(författare)
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Some aspects of release and transport of gases in deep granitic rocks : possible implications for nuclear waste repositories
- 2013
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 21:8, s. 1701-1716
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Tidskriftsartikel (refereegranskat)abstract
- Radon, radium and helium data from three sites in granitic rock in Sweden (Forsmark and Laxemar) and Finland (Olkiluoto) from depths greater than 1,000 m were interpreted by a model that describes how daughter nuclides, including helium from uranium and thorium decay, escape from minerals, enter the pore water in the rock matrix and diffuse to the seeping water in the fractures in the rock. The radium concentrations are on the order of < 30 Bq/l of water that has recently infiltrated and then emerged from the rock. Radon concentrations are mostly several orders of magnitude larger. The model predicts values in the same range. The fair agreement between model results, field data and laboratory data over a scale spanning micrometres over meters to kilometres, and time scales of days to millions of years, shows that the micropores of the rock matrix are connected even at depths down to and beyond a kilometre. Molecular diffusion in the matrix pore water is a key migration mechanism. Laboratory-derived sorption coefficients for radium are of the same magnitude as those needed in the modelling of the in situ data to give good agreement.
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