Using official map data on topography, wetlands and vegetation cover for prediction of stream water chemistry in boreal headwater catchments

摘要

A large part of the spatial variation of stream waterchemistry can be related to inputs from headwater streams. In order tounderstand and analyse the dominant processes taking place in small andheterogeneous catchments, accurate data with high spatial and temporalresolution is necessary. In most cases, the quality and resolution ofavailable map data are considered too poor to be used in environmentalassessments and modelling of headwater stream chemistry. In this study 18forested catchments (1–4 km2) were selected within a 120×50 km regionin the county of V?rmland in western Sweden. The aim was to test iftopographic and vegetation variables derived from official datasets werecorrelated to stream water chemistry, primarily the concentration ofdissolved organic carbon (DOC), but also Al, Fe and Si content. GIS was usedto analyse the elevation characteristics, generate topographic indices, andcalculate the percentage of wetlands and a number of vegetation classes. Theresults clearly show that topography has a major influence on stream waterchemistry. There were strong correlations between mean slope and percentagewetland, percentage wetland and DOC, mean slope and DOC, and a very strongcorrelation between mean topographic wetness index (TWI) and DOC. Theconclusion was that official topographic data, despite uncertain or of lowquality and resolution, could be useful in the prediction of headwaterDOC-concentration in boreal forested catchments.