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A GIS-based landscape analysis of dissolved organic carbon in boreal headwater streams
Karlstad University, Faculty of Social and Life Sciences, Department of Biology. (Biologi)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In boreal catchments, stream water chemistry is influenced and controlled by several landscape factors. The influence of spatially distributed variables is in turn dependent on the hydrological scale. Headwater streams have larger variability of water chemistry, and thus together represent a large biodiversity, and therefore need to be monitored in official environmental assessments. One objective of this study was, using Geographical Information Systems (GIS), to analyse co-variation between landscape variables and water chemistry and to determine which of the landscape variables have a major influence on the concentration of dissolved organic carbon (DOC) in headwater streams. Another objective was to find a simple method for predicting sources of DOC, using official map data and publically available GIS applications.

Totally 85 headwater catchments (0.1-4 km2) in the county of Värmland, western south Sweden, were used in the study. Water chemistry was analysed for water sampled at low, medium and high flows, and landscape variables were extracted from official map data sources: topographic maps, a digital elevation model (DEM, 50 m grid), and vegetation data. Statistical analyses showed that topography (mean slope and mean topographic wetness index (TWI)) and wetland cover often correlated well with DOC in headwater catchments. Official map data could satisfactorily extract landscape variables (mean slope, mean TWI) that were useful in predicting stream water chemistry (DOC).

A high-resolution elevation model, which was generated by interpolation of photogrammetric data, was used to calculate and evaluate two different wetness indices and their ability to predict the occurrence of wetlands in six catchments of different sizes and topography. The SAGA (System for Automated Geoscientific Analyses) wetness index (SWI) gave substantially better results than the TWI. The effects of resolution of DEMs on calculations of the SWI were investigated using 5, 10, 25 and 50 m grids. The results showed that SWI values increased with increasing cell size. The near linear increment of mean values for resolutions 10-50 m suggests a independence of terrain type and catchment size, which supported previous findings that indicated that mean slope and mean wetness index calculated from coarse elevation models may be used for prediction of DOC in headwater streams.

 

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet , 2009. , p. 49
Series
Karlstad University Studies, ISSN 1403-8099 ; 2009:38
Keywords [en]
boreal forests, wetlands, vegetation types, headwater streams, catchment hydrology, streamwater chemistry, DOC, GIS, terrain analysis, DEM, slope, wetness index, TWI
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-2925ISBN: 978-91-7063-206-8 (print)OAI: oai:DiVA.org:kau-2925DiVA, id: diva2:113724
Public defence
2009-10-02, Geijersalen, 12A138, Karlstads universitet, Karlstad, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2009-09-24 Created: 2008-10-24 Last updated: 2011-10-04Bibliographically approved
List of papers
1. Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams
Open this publication in new window or tab >>Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams
2008 (English)In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, no 22, p. 1965-1975Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
boreal, landscape, catchment hydrology, headwater streams, streamwater quality, DOC, wetland, GIS
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-4672 (URN)10.1002/hyp.6779 (DOI)
Available from: 2009-09-14 Created: 2009-09-14 Last updated: 2017-12-13Bibliographically approved
2. Using official map data on topography, wetlands and vegetation cover for prediction of stream water chemistry in boreal headwater catchments
Open this publication in new window or tab >>Using official map data on topography, wetlands and vegetation cover for prediction of stream water chemistry in boreal headwater catchments
2009 (English)In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, p. 537-549Article in journal (Refereed) Published
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-4673 (URN)10.5194/hess-13-537-2009 (DOI)
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2017-12-13Bibliographically approved
3. Influence of wetland restoration on hydrology and water chemistry in a Swedish boreal catchment
Open this publication in new window or tab >>Influence of wetland restoration on hydrology and water chemistry in a Swedish boreal catchment
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Identifiers
urn:nbn:se:kau:diva-4674 (URN)
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2017-12-06Bibliographically approved
4. Wetness indices as predictors of boreal wetlands
Open this publication in new window or tab >>Wetness indices as predictors of boreal wetlands
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-4675 (URN)
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2017-12-06Bibliographically approved
5. DEM resolution effects on SAGA wetness index in boreal forested catchments
Open this publication in new window or tab >>DEM resolution effects on SAGA wetness index in boreal forested catchments
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-4676 (URN)
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2011-10-05Bibliographically approved

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