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- Amvrosiadi, Nino
(författare)
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The value of experimental data and modelling for exploration of hydrological functioning: The case of a till hillslope
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Successfully modeling one system response (e.g. hydrograph or solute transport) sometimes gives the false sense of well-characterizing the modeled system. This is partly because of the well-known equifinality issue; during the calibration process multiple parameter combinations can produce similarly good results. One step forward towards a better-defined system is using measured (at relevant scale) values for the model parameters, as well as using multiple conditions to constrain the model.But when not enough, or relevant, field measurements are available, virtual experiments (VE’s) can be used as a supplementary method to model calibration. The advantage of VE’s over model calibration is that they can also be used to explore assumptions both on the system hydrological processes, and on the model structure.One goal of this study was to utilize both field measurements and models for better characterization of the S-transect hillslope, located in Västrabäcken catchment, Northern Sweden. This included (a) characteristics in space: system vertical boundaries, hydraulic parameters, pore water velocity distribution, spatial correlation of flowpaths, soil water retention properties; (b) characteristic of system’s dynamic behavior: storage – discharge relationship, transit time distribution, turnover time; and (c) outputs’ sensitivity to external forcing, and to small scale structure assumptions. The second goal was to comment on the value of field measurements and virtual experiments for extracting information about the studied system.An intensely monitored study hillslope was chosen for this work. Although the hillslope has already been the subject of multiple field and modelling studies, there are still open questions regarding the characteristics listed above. The models used were the Vertical Equilibrium Model (VEM), and the Multiple Interacting Pathways (MIPs) model.It was found that the hillslope was well connected; from the near-stream areas up to the water divide the storage – discharge relationship could be described as an exponential function. Also, the dynamic storage (which controls the hydrograph dynamics) was much smaller comparing to the total hillslope storage. The unsaturated soil storage was found to be more sensitive to water table positions than vertical flux magnitude. The dynamic condition of external forcing (precipitation and evapotranspiration) affected the transit time distribution (TTD) shape. And, opposite to expectations, TTD was not sensitive to micro-scale structural assumptions tested here.
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- Apler, Anna, 1980-
(författare)
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Dispersal and environmental impact of contaminants in organic rich, fibrous sediments of industrial origin in the Baltic Sea
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The health of the Baltic Sea is negatively affected by hazardous substances such as metals and persistent organic pollutants (POPs), which include legacy pollutants that were banned decades ago, but still circulate in the ecosystem. Elevated levels of legacy pollutants, identified by HELCOM as key hazardous substances, have been found in accumulations of fibrous sediments, so-called fiberbanks and fiber-rich sediments, which derive from old pulp mills along the Swedish north coast. The fiberbanks are deposited in shallow water and bathymetrical models show evidence of their erosion, potentially caused by propeller wash, submarine landslides and gas ebullition. This thesis addresses the potential dispersal of key substances from three fiberbank sites located in a non-tidal Swedish estuary, in which metals and POPs are present in concentrations that may pose a risk for benthic organisms. Metals and POPs are partitioned to organic material and, as expected, show the highest partitioning coefficients (KD) in fiberbanks that have higher TOC levels compared to adjacent areas with fiber-rich sediments (natural clay sediments mixed up with fibers) or relatively unaffected postglacial clays. However, many analytes were found to be present in quantifiable concentrations in pore water, which indicates diffusion of substances from the solid phase to the aqueous phase. To assess the dispersive influence of an abrupt erosional event on dispersion, metals were measured in undisturbed bottom water and in bottom water disturbed by artificial re-suspension of fibrous sediments. The bioavailable, dissolved fraction of metals decreased in bottom water after re-suspension, probably due to the particle concentration effect. In contrast, the total concentrations of metals and number of quantifiable metals increased with particle concentration caused by re-suspension. At one station, the total concentration of chromium (Cr) was elevated to a level where it may lower the ecological status of the water body during periods of substantial erosion (e.g. spring floods or submarine landslides). Analyses of disturbed bottom water revealed, however, that minerogenic particles were preferentially re-suspended compared to organic. This suggests that physical erosion and re-suspension of fiberbank sediments might have a larger effect on dispersal of metals than on POPs.
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- Bishop, Kevin, et al.
(författare)
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A primer for hydrology : the beguiling simplicity of Water's journey from rain to stream at 30 Preface
- 2015
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 29:16, s. 3443-3446
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Water's journey from rain to stream by Harald Grip and Allan Rodhe (1985, in Swedish: Vattnets vag fran regn till back) was one of the first textbooks to present groundwater contributions as a major feature of runoff generation, with implications for water quality and management. Three decades later, we have the privilege of presenting a special issue of Hydrological Processes, Runoff Generation in a Nordic Light: 30Years with Water's Journey from Rain to Stream' that seeks to introduce the book to a larger audience and continue the journey of ideas that the authors set in motion with their book.
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- Bishop, Kevin, et al.
(författare)
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EviWet: Evidensbaserat beslutsstöd för våtmarkers hydrologiska ekosystemtjänster
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Vissa våtmarker kan jämna ut höga och låga vattenflöden i naturen, och därigenom mildra översvämningar och torka. Hur väl en våtmark förmår att dämpa extremflöden beror på var i naturen de ligger och vilken sorts våtmarkstyp det är. Vi vet för lite om våtmarkers hydrologiska egenskaper och betydelsen av placering i landskapet. Forskarna i EviWet har undersökt torvens vattenhållande förmåga, och därifrån skapat modeller för ekohydrologi, samt utvecklat beslutsstöd för operationell modellering. Projektet har finansierats med Formas medel för det Nationella forskningsprogrammet om klimat men administrerats av Naturvårdsverket.
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- Bishop, Kevin, et al.
(författare)
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Nature as the "Natural" Goal for Water Management : A Conversation
- 2009
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Ingår i: Ambio. - : Springer Netherlands. - 0044-7447 .- 1654-7209. ; Volume 38:Issue 4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The goals for water-quality and ecosystem integrity are often defined relative to "natural" reference conditions in many water-management systems, including the European Union Water Framework Directive. This paper examines the difficulties created for water management by using "natural" as the goal. These difficulties are articulated from different perspectives in an informal (fictional) conversation that takes place after a workshop on reference conditions in water-resources management. The difficulties include defining the natural state and modeling how a system might be progressed toward the natural, as well as the feasibility and desirability of restoring a natural state. The paper also considers the appropriateness for developing countries to adopt the use of natural as the goal for water management. We conclude that failure to critically examine the complexities of having "natural" as the goal will compromise the ability to manage the issues that arise in real basins by not making the ambiguities associated with this "natural" goal explicit. This is unfortunate both for the western world that has embraced this model of "natural as the goal" and for the developing world in so far as they are encouraged to adopt this model.
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- Bishop, Kevin, et al.
(författare)
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Relation between land use change for long- term trends of organic carbon in lake water and its importance for acidification assessment
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This study examines the changes of total organic carbon (TOC) concentrations in 20 Swedish lakes throughout Sweden using pre-industrial (1860) TOC0 inferred from near-infrared spectrometry (TOCNIRS) of lake sediments to determine if land use change over time could be a plausible explanation for changes in lake water TOC. The study also focuses on the importance of using inferred pre-industrial data of lake water pH and TOC for acidification assessment, in particular ANC0. Most lakes in this study show a long-term decreasing trend of TOC from 1860 up to -0.45 mg/l/yr-1 to an identified breaking point where the TOC turns from decreasing to increasing. Fifteen of the lakes have a breaking point in the mid to late 20th century (1950-1980) while five lakes do not display a clear breaking point. The magnitude of the increasing trend of TOC after the breaking point is up to 0.16 mg/l/yr-1 . Changes in land use were studied by comparing historical maps with present databases of land use. Land use changes in the catchment area show substantial differences in forest cultivation; for instance the coniferous forest has increased by 26% on average. This increase is due to removal of native forest (deciduous forest) and removal of wetlands. Two major conclusions can be drawn from the effects of land use change on TOC levels: (I) No direct correlation between land use change and long-term trends of TOC could be identified in this study. Previous studies have identified the effects of land use change on the carbon storage in the catchment area that corresponds well with the findings of this study. (II) the character of the forest land plays an important role when discussing the effects of land use change for long term TOC trends. The change from open-ended forests with large trees to intense managed forest is considered as an important driving force for TOC. To determine reference conditions there is a need to make good estimations of ANC0 for acidification assessment in Swedish lakes. This study examines the precision of MAGIC model ANC0 calculations (ANC0-MAGIC) against ANC0 calculated with TOCNIRS, diatom-pH and calculated pCO2 (ANC0, diatom-NIRS). ANC0, diatom-NIRS shows a mean difference of (-31µeq/l) when comparing it with ANC0-MAGIC. In comparison, when using contemporary TOC (TOCt) mean lake value 1990-2005 (ANC0,diatom-TOC) the results show a mean difference of (-0.45 µeq/l) in comparison with ANC0-MAGIC. A better fit is generated with TOCNIRS then TOCt. This could be an indication that ANC0- MAGIC overestimates the acidification of Swedish lakes. The European Union’s “Water 8 Framework Directive”, which Sweden has implemented, requires that all surface waters within the Union’s authority have achieved good ecological status by 2015. According to the ecological quality standard the differences between the pre-industrial pH and contemporary pH, i.e. ΔpH=pH0-pHt, should not be more than 0.4 units. This study shows that the long-term trends have to be accounted for when calculating reference conditions and ecological status for acidification
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