Twentieth century water quality trends in Minnesota lakes compared with presettlement variability

Twentieth century water quality trends in Minnesota lakes compared with presettlement variability

2004-05-18

A diatom-based transfer function was used to reconstruct water chemistry before European settlement in 55 Minnesota lakes. The lakes span three natural ecoregions, which differ in their history of land use, as well as in surficial geology, climate, and vegetation. Postsettlement trends were compared with water chemistry change reconstructed from two presettlement core sections (circa 1750 and 1800) as a measure of natural variability. Presettlement water quality changes were generally small and nondirectional in all three ecoregions. In contrast, half of the urban lakes showed a statistically significant increase in chloride, whereas 30% of urban and 30% of agricultural region lakes record a statistically significant increase in total phosphorus between 1800 and the present. These changes, which are attributed to road salt and nutrient runoff, are strongly correlated with the percentage of watershed area that is developed (residential or urban) in the case of chloride increases and the percentage of developed (metropolitan areas) or agricultural (agricultural areas) land in the case of nutrient increases. Water quality has changed little since 1800 for lakes in the forested regions of northeastern Minnesota. The few changes that are seen in this region are likely related to natural variations in climate or catchment soils.

Ramstack, Joy M.
Fritz, Sherilyn C.
Engstrom, Daniel R.

Department of Earth and Environmental Sciences Lehigh University,
Department of Geosciences and School of Biological Sciences University of Nebraska
St. Croix Watershed Research Station Science Museum of Minnesota

Minnesota Pollution Control Agency

NRC Research Press (Ottawa, Ontario)

Water Monitoring & Assessment
Water Quality & Pollutants

Urban water contamination
Ecoregions
Land use
Water chemistry

2000-2009

Yes

https://www.pca.state.mn.us/water/sediment-studies-twin-cities-and-state...

Creative Commons

NRC Research Press