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Sökning: WFRF:(Nyberg Lars 1962 ) > (2005-2009)

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1.
  • Andersson, Jan-Olov, 1966-, et al. (författare)
  • Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams
  • 2008
  • Ingår i: Hydrological Processes. - 0885-6087. ; :22, s. 1965-1975
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to investigate the relation between water chemistry and functional landscape elements, spatial data sets of characteristics for 68 small (0·2–1·5 km2) boreal forest catchments in western central Sweden were analysed in a geographical information system (GIS). The geographic data used were extracted from official topographic maps. Water sampled four times at different flow situations was analysed chemically. This paper focuses on one phenomenon that has an important influence on headwater quality in boreal, coniferous forest streams: generation and export of dissolved organic carbon (DOC). It is known that wetland cover (bogs and fens) in the catchment is a major source of DOC. In this study, a comparison was made between a large number of headwater catchments with varying spatial locations and areas of wetlands. How this variation, together with a number of other spatial variables, influences the DOC flux in the streamwater was analysed by statistical methods. There were significant, but not strong, correlations between the total percentages of wetland area and DOC flux measured at a medium flow situation, but not at high flow. Neither were there any significant correlations between the percentage of wetland area connected to streams, nor the percentage of wetland area within a zone 50 m from the stream and the DOC flux. There were, however, correlations between catchment mean slope and the DOC flux in all but one flow situations. This study showed that, considering geographical data retrieved from official sources, the topography of a catchment better explains the variation in DOC flux than the percentage and locations of distinct wetland areas. This emphasizes the need for high-resolution elevation models accurate enough to reveal the sources of DOC found in headwater streams.
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3.
  • Calles, Olle, 1974-, et al. (författare)
  • Temporal and spatial variation in quality of hyporheic water in one unregulated and two regulated boreal rivers
  • 2007
  • Ingår i: River Research and Applications. - John Wiley & Sons, Ltd.
  • Tidskriftsartikel (refereegranskat)abstract
    • This study describes the temporal and spatial variations in hyporheic water quality in three boreal rivers, the River Tobyälven, an unregulated river, the river Mangälven, a regulated river with a minimum discharge requirement and the river Järperudsälven, a<br/><br/>regulated river without any minimum discharge requirements. A total of 43 permanent piezometers were used to measure dissolved oxygen (DO), temperature, electrical conductivity, pH, NO3 and NH4 in the hyporheic water at 150mm and 300mm depth, at monthly intervals from October 2001 to October 2002. Another seven piezometers were installed in brown trout redds and monitored during the incubation period, from December 2001 to April 2002. In the river Tobyälven, temporal patterns in hyporheic water chemistry correlated to variations in surface water chemistry and discharge. In the river Jäperudsälven, the hyporheic water chemistry did not correlate to discharge or surface water chemistry. In the river Mangälven, the water chemistry was dominated by releases from a large upstream lake, and there were weak correlations between surface water chemistry and<br/><br/>hyporheic water chemistry at some sites. The incubation conditions for brown trout eggs were most favourable in the unregulated river, characterized by high DO levels that remained high throughout the incubation period. In the river Järperudsälven the DO<br/><br/>levels were variable during spawning, and then gradually declined to critically low levels during incubation, whereas in the river Mangälven the DO conditions were intermediate and stable. Thus we observed a stronger coupling between surface water<br/><br/>conditions and hyporheic conditions, i.e. vertical connectivity, in the unregulated river than in the regulated river with minimum flow requirements, which in turn was stronger than in the river without minimum flow requirements. Copyright # 2007 John<br/><br/>Wiley & Sons, Ltd
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4.
  • Johansson, Magnus, 1970-, et al. (författare)
  • Evaluating the range of perspectives on lessons-learning from the 2005 storm in Sweden
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • Lessons learning from systematic analyses of past natural disasters is of great importance for future risk reduction and vulnerability management. It is one crucial piece of a puzzle towards disaster resilient societies, together with e.g. models of future emerging climate-related risks, globalization or demographic changes. Systematic analyses of impact and management of past events have commonly been produced in many sectors, but the knowledge is seldom shared outside the own organization or produced for other actors. LPHC (low probability high consequences) disasters usually comprise most analytical activities, since they often are met with surprise and highlight the failure to integrate resilience into normal societal planning. During the last 50 years, several LPHC events in Sweden have functioned as alarm clocks and entailed major changes and improvements in government policies or legislations, safety management systems, risk assessments, response training, stakeholder communication, etc. Such an event occurred in January 2005 when Northern Europe was confronted with one of the most severe storms in modern history. Accidents that caused 24 fatalities occurred (17 in Sweden), several regions in UK and Germany were flooded and extensive areas of storm-felled forests left nearly one million households in Scandinavia without electricity. In Sweden the quantity of storm-felled trees was equivalent to the combined volume felled by other storms during the whole of the 20th century, which caused exceptional damage to forests, roads, railways and electricity and telecommunications networks, including cell-phones. Follow-ups and evaluations at local level, as regulated by law, together with government commissions to central authorities and interest from research communities, have resulted in an extensive production of documented lessons learning. The production of in total 24 reports, 7 scientific articles and 2 economic reports from business associations divides thematically quite equally within coping capacity and exposed and susceptible elements. Most attention allots crisis management and response issues (45 %). Only one attempt is made to present a holistic view of the event and it is not a law bounded initiative. Evaluations from other recent events, e.g. the flood 2000 in Arvika and the landslide at Munkedal 2006, show the same clear focus on crisis management and less or none consideration taken to environmental, social or socioeconomic consequences. It reflects the traditional political financial will to invest in a high level on response capacity on expense of preventive work
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5.
  • Johansson, Magnus, 1970-, et al. (författare)
  • Learning lessons from natural disasters sectorial or holistic perspectives?
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • Lessons learning from systematic analyses of past natural disasters is of great importance for future risk reduction and vulnerability management. It is one crucial piece of a puzzle towards disaster resilient societies, together with e.g. models of future emerging climate-related risks, globalization or demographic changes. Systematic analyses of impact and management of past events have commonly been produced in many sectors, but the knowledge is seldom shared outside the own organization or produced for other actors. To increase the availability of reports and documents, the Swedish Rescue Services Agency has created the Swedish Natural Hazards Information System, in accordance with a government commission from 2005. The system gathers accident reports, investigations and in-depth analyses, together with societal additional costs and mappings of consequences from central and local governments, NGOs and private actors. Evaluation of the collection reveals large differences in quality, systematic approach, depth and extent, clearly consistent with the lack of coherent harmonization of investigation and reporting approaches. Type of hazard, degree of impact and time elapsed since present are decisive for the collectedvolume. LPHC (low probability high consequences) disasters usually comprise most data and analytical activities, since they often are met with surprise and highlight the failure to integrate resilience into normal societal planning. During the last 50 years, several LPHC events in Sweden have functioned as alarm clocks and entailed major changes and improvements in government policies or legislations, safety management systems, risk assessments,response training, stakeholder communication, etc. Such an event occurred in January 2005 when Northern Europe was confronted with one of the most severe storms in modern history. Accidents that caused 24 fatalities occurred (17 in Sweden), several regions in UK and Germany were flooded and extensive areas of storm-felled forests left nearly one million households in Scandinavia without electricity. In Sweden the quantity of storm-felled trees was equivalent to the combined volume felled by other storms during the whole of the 20th century, which caused exceptional damage to forests, roads, railways and electricity and telecommunications networks, including cellphones. Follow-ups and evaluations at local level, as regulated by law, together with government commissions to central authorities and interest from research communities, have resulted in an extensive production of documented lessons learning. Our case study describes their thematic extent, identifies different perspectives in relation to their basis for analyses, emphasizes the complementary need of a holistic perspective and puts the Swedish systematic procedure into an international comparison
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6.
  • Nyberg, Lars, 1962-, et al. (författare)
  • Impact of short-term regulation on hyporheic water quality in a boreal river
  • 2008
  • Ingår i: Rivers Research and Applications : an international journal devoted to river research and management. - 1535-1459. ; 24:4, s. 407-419
  • Tidskriftsartikel (refereegranskat)abstract
    • Water regulation may alter hydraulic head gradients with consequences for the exchange of water between the river and the hyporheic zone. The objective of this study was to investigate the effect of discharge on hyporheic water quality in a regulated Swedish boreal river during a 10-day experimental period with a sequence of alternating high- and low-flow episodes. A 250 m reach was instrumented with 28 piezometers placed at 150 and 300 mm below the river bed or below the mean groundwater level in the floodplain, and these piezometers were used to measure temperature, oxygen, electric conductivity and pH. High daily variation in air temperature during the first 3 days was transmitted vertically through the stream water into the hyporheic zone within hours. An oxygen saturation of 100% in the river water corresponded to 60–70% saturation at 150 mm depth and 30% at 300 mm depth. The hyporheic oxygen concentration at 150 mm depth decreased during the experimental period, falling into a range that is potentially harmful to incubating salmonid eggs. This was interpreted as a long-term response to the overall regulation regime, rather than a response to short-term water regulation during the experiment. Even though the effect of short-term regulation on the quality of hyporheic water in the river bed was limited, there was a more pronounced effect on the quality of floodplain hyporheic water. Most of the driving forces for temporal variation of water quality in the river bed came vertically from the river water, rather than from the lateral exchange.
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