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River nutrient loads and catchment size
Centro de Investigacio´n Cientı´fica y de Educacio´n Superior de Ensenada (CICESE), Departamento de Ecologı´a, Ensenada, Baja California, Mexico.
Boyce Thompson Institute, Cornell University, Ithaca, NY 14850, USA.
Kansas Geological Survey, University of Kansas, Lawrence, KS 66047, USA.
National Institute of Water and Atmospheric Research (NIWA), P.O. Box 11-115, Hamilton, New Zealand.
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2005 (English)In: Biogeochemistry, ISSN 0168-2563, Vol. 75, 83-107 p.Article in journal (Refereed) Published
Abstract [en]

We have used a total of 496 sample sites to calibrate a simple regression model for calculating dissolved inorganic nutrient fluxes via runoff to the ocean. The regression uses the logarithms of runoff and human population as the independent variables and estimates the logarithms of dissolved inorganic nitrogen and phosphorus loading with R2 values near 0.8. This predictive capability is about the same as has been derived for total nutrient loading with process-based models requiring more detailed information on independent variables. We conclude that population and runoff are robust proxies for the more detailed application, landscape modification, and in-stream processing estimated by more process-based models. The regression model has then been applied to a demonstration data set of 1353 river catchments draining to the sea from the North American continent south of the Canadian border. The geographic extents of these basins were extracted from a 1-km digital elevation model for North America, and both runoff and population were estimated for each basin. Most of the basins (72% of the total) are smaller than 103 km2, and both runoff and population density are higher and more variable among small basins than among larger ones.While total load to the ocean can probably be adequately estimated from large systems only, analysis of the geographic distribution of nutrient loading requires consideration of the small basins, which can exhibit significant hydrologic and demographic heterogeneity between systems over their range even within the same geographic region. High-resolution regional and local analysis is necessary for environmental assessment and management.

Place, publisher, year, edition, pages
Springer , 2005. Vol. 75, 83-107 p.
URN: urn:nbn:se:su:diva-32492DOI: 10.1007/s10533-004-6320-zOAI: diva2:280736
Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2009-12-14Bibliographically approved
In thesis
1. Nitrogen land-sea fluxes in the Baltic Sea catchment: Empirical relationships and budgets
Open this publication in new window or tab >>Nitrogen land-sea fluxes in the Baltic Sea catchment: Empirical relationships and budgets
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis empirical relationships and modeling tools are used to describe the relationship between human activities and meso- and large scale riverine N fluxes from land to sea.

On a large scale Paper I showed that by only having knowledge about human population size and runoff one can estimate the riverine export of DIN (r2= 0.76). In Paper II we included two other important anthropogenic N inputs, i.e. atmospheric deposition and primary emission (PE) from animals. In most of the catchments the PE from animals were larger than the PE from humans. Hence, development of livestock is important and increased animal protein consumption by humans might increase the riverine N export. Scenario analysis (Paper II) show that climate change is expected to both decrease and increase the riverine N export depending on which part of the catchment is modeled.

In the southern and eastern parts of the Baltic Sea catchment there is large potential for N reductions from point sources (Papers III & V). The diffuse sources are more difficult to decrease and a reduction of mineral fertilizer does not always lead to reduced N loadings because the agricultural systems can buffer even a slight surplus (Paper III). There is inertia in the catchments which can be seen in for example in the northern part of the catchment. Here atmospheric N deposition is almost as high as in the southern part but the nitrogen flux from these rivers is not elevated. These northern river catchments have N exports of the same magnitude as the natural background (Paper IV), indicating that the atmospheric N deposition is retained in the system and probably taken up by N limited boreal forests. However, important reductions can be achieved in the agricultural sector by detailed management of the planted land and animal manure. The highest sensitivity is in catchments with high animal density and high specific discharge, primarily draining to Kattegat and Danish Straits (Paper II & IV).

Place, publisher, year, edition, pages
Stockholm: Department of Applied Environmental Science (ITM), 2010. 40 p.
Nitrogen fluxes, Baltic Sea, primary emissions, riverine export, Scenario analysis, climate change, animal protein consumption, fertilizer use
National Category
Environmental Sciences
Research subject
Applied Environmental Science
urn:nbn:se:su:diva-32493 (URN)978-91-7155-988-3 (ISBN)
Public defence
2010-01-29, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
At the time of doctoral dissertation the following publications were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: ManuscriptAvailable from: 2010-01-07 Created: 2009-12-11 Last updated: 2010-01-27Bibliographically approved

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Humborg, ChristophEriksson Hägg, HannaHannerz, Fredrik
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Department of Applied Environmental Science (ITM)Department of Systems EcologyDepartment of Physical Geography and Quaternary Geology
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