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Doctoral thesis, 2003

Variation in lake water chemistry and spatial scale

Göransson, Elisabet

Abstract

Lake water chemistry generally reflects the ecological, geological and climatic processes in and around a lake. Spatial variability both within and among lakes affects our interpretation of lake monitoring data. This thesis addresses the importance of scale, from small (variability within a lake and among neighboring lakes) to large (ecoregions, EMEP-grid and parts of the country) on selected chemical metrics using data from the Swedish lake monitoring program. Different approaches are used when studying the spatial variability of lake water chemistry, e.g. partial least squares regression (PLS) and variogram modeling. The synchronous variation of lake water chemistry is also investigated. Paper I addressed the question of how representative a mid-lake surface sample was of in-lake conditions. Where a sample was taken within a lake was found to affect the sample’s representativity of lake water surface chemistry. As a mid-lake sample was shown to be more representative than a random sample, my conclusion was that a mid-lake sample can be considered representative of average surface water chemistry. Partition lakes regarding lake water chemistry is an important issue for interpreting lake monitoring data. In Paper II lakes were classified into six ecoregions. The study showed that ecoregional classification of lake water chemistry only worked in the southern part of Sweden, where there was sufficient variation within the ecoregions. Both Paper III and IV indicated that water-chemical data should be interpreted at a regional scale (e.g. EMEP-scale). In Paper III I showed that there was a spatial dependence in lake water chemistry; Ca* and Mg* concentrations in lakes close to each other were more similar than in lakes at further distances, but the distance for dependence can vary within the country. Paper IV showed that lakes seemed to have high rate of synchronous variation at least for the variables SO4*, Ca*, AbsF and ANC. Further knowledge of the connection between variation in lake water chemistry and e.g. weathering, soil chemistry, soil type, distribution of mires, land use, precipitation, deposition and runoff are needed. An interesting task would be to develop a method to classify the country into regions regarding lake water chemistry together with experts in geology and hydrology. o

Keywords

regionalization; predictive models; pH; total phosphorus; catchment characteristics; geostatistics; liming; synchrony; lake characteristics; lake survey

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2003, number: 269
ISBN: 91-576-6503-6
Publisher: Dept. of Environmental Assessment, Swedish University of Agricultural Sciences

Authors' information

Göransson, Elisabet
Swedish University of Agricultural Sciences, Department of Environmental Assessment

UKÄ Subject classification

Meteorology and Atmospheric Sciences

URI (permanent link to this page)

https://res.slu.se/id/publ/79724