Chlorophyll a, the most widely used measure of algal abundance, varies widely across Minnesota’s lakes and also exhibits large variations during the open-water season. Map at right shows range of chlorophyll a, in Lake Minnetonka and nearby lakes in the west metro Twin Cities in summer 2018. For more details, see our chlorophyll page.
Eve Daniels, videographer, shoots B-roll film on a gorgeous June day on beautiful Big Sandy Lake for two videos that our group developed to describe what CDOM is, how it affects lake ecology and human uses of lakes, and how CDOM can be measured. For more information, see the CDOM page under Metrics of Surface Water Quality.
As part of an NSF citizen science project, we are exploring the use of smartphone cameras to measure CDOM levels. Two approaches are being explored: photos of Secchi disks suspended at 1 ft. depth or a white bucket filled with lake water. Photos of the disk above water or the empty bucket are used to account for varying light conditions. Photo at right shows postdoc Ben Ma conducting a rooftop experiment to compare results from different smartphone models.
The Minnesota LakeBrowser has provided satellite-derived water clarity, an indicator of water quality, data for more than 10,000 Minnesota lakes since 2002. It was recently updated with new data on lake clarity and additional water quality variables (CDOM and chlorophyll). Enhanced capabilities have been added to display images, data and maps of geospatial patterns, show temporal trends, and provide data access and download.
With financial support from the Minnesota’s Pollution Control Agency and Environment and Natural Resources Trust Fund, Leif Olmanson, remote sensing scientist in our group (shown at right), recently completed four additional (2010, 2011, 2015 and 2018) statewide assessments of water clarity (Secchi depth) of Minnesota lakes, which now extend from 1975 to 2018. For complete results, go to the LakeBrowser.