Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 9 2009 10.5194/hess-13-1597-2009 http://www.hydrol-earth-syst-sci.net/13/1597/2009/ http://www.hydrol-earth-syst-sci.net/13/1597/2009/hess-13-1597-2009.html http://www.hydrol-earth-syst-sci.net/13/1597/2009/hess-13-1597-2009.pdf 1597 1606 2009-09-09 Landscape elements and river chemistry as affected by river regulation – a 3-D perspective E. Smedberg erik@mbox.su.se C. Humborg M. Jakobsson C.-M. Mörth Baltic Nest Institute, Stockholm Resilience Centre, 10691 Stockholm, Sweden Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden We tested the hypothesis whether individual land classes within a river catchment contribute equally to river loading with dissolved constituents or whether some land classes act as "hot spots" to river loading and if so, are these land classes especially affected by hydrological alterations. The amount of land covered by forests and wetlands and the average soil depth (throughout this paper soil refers to everything overlying bedrock i.e. regolith) of a river catchment explain 58–93% of the variability in total organic carbon (TOC) and dissolved silicate (DSi) concentrations for 22 river catchments in Northern Sweden. For the heavily regulated Luleälven, with 7 studied sub-catchments, only 3% of the headwater areas have been inundated by reservoirs, some 10% of the soils and aggregated forest and wetland areas have been lost due to damming and further hydrological alteration such as bypassing entire sub-catchments by headrace tunnels. However, looking at individual forest classes, our estimates indicate that some 37% of the deciduous forests have been inundated by the four major reservoirs built in the Luleälven headwaters. 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