In the News

May 2019: 


The Lake Browser was updated recently with new statewide data on lake clarity for 2015, the distribution of CDOM in Minnesota lakes in 2015 and 2016-17, as well as summer chlorophyll-a concentrations for 2017-18. The graphic at the right shows the wide range of chlorophyll occurring in the many basins of Lake Minnetonka and in nearby lakes of the metro area west of Minneapolis. The search and display capabilities of the Browser currently are being expanded (expect more news on this in a few months), and new data will be added as they become available.

Leif Olmanson and Ben Page presented papers at the European Space Agency, 2019 Living Planet Symposium in Milan, Italy in May. One paper described the group’s advances on lake water quality monitoring capabilities using Sentinel and Landsat imagery and automated high-performance computing, and the other described evaluation of atmospheric correction methods for inland water quality mapping. In collaboration with Chris Crawford from the USGS EROS Center, they also presented a poster on use of Sentinel-1 synthetic aperture radar remote sensing to characterize under-ice limnology and in-lake primary productivity. As part of their visit to Italy, they participated in a data collection campaign on Lake Garda with remote sensing scientist, Claudia Giardino, and visited the Lake Garda Experimental Station Eugenio Zilioli.

Jacques Finlayand his lab are collaborating with the newly formed Regional Monitoring Network for inland lakes to increase the integration of CDOM data into spatial and temporal analyses of water quality change. The RMN is a partnership among states, tribes and other groups to develop and integrate monitoring across thousands of lakes in the Northeast and Midwest US. Finlay’s lab is supporting interested RMN members through provision of information from our work, advice on methods, and in some cases analyses to allow expansion of CDOM data collection within the network. The RMN recently was described in a 2018 article by RMN coordinator Jen Stamp in the NALMS newsletter, Lakeline.

Patrick Brezonik is the lead author of two recently published articles that describe results from our CDOM work. A paper on the importance of CDOM in limiting Secchi depth (SD) in colored lakes and the implications for use of SD as a trophic state metric was published in Ecological Applications in March. This work was a collaboration between our group and scientists from the Minnesota Pollution Control Agency. Coauthors include Will Bouchard and Jesse Anderson from the MPCA, as well as Jacques Finlay, Claire Griffin, Leif Olmanson, Bill Arnold and Ray Hozalski. A paper that details findings on dissolved iron-CDOM interactions and the limited role of dissolved iron in affecting the color intensity of CDOM was published in PLOS ONE in February . Coauthors on the paper are Jacques Finlay, Claire Griffin, Bill Arnold, Evelyn Boardman, Noah Germolus, Ray Hozalski, and Leif Olmanson.

Claire Griffin began a new postdoc position at the University of Virginia in February, 2019, working on interactions between built and natural environments in the Arctic. Griffin will continue working with our group in writing several papers related to the CDOM work she did with us since 2016. Griffin also gave an oral presentation at the American Geophysical Union (AGU) fall meeting in Washington, DC, December 10-14, 2018 on regional-scale measurement of dissolved organic carbon pools in lakes using remote sensing techniques. Griffin and Patrick Brezonik also presented a poster in a session on citizen science at the fall AGU meeting on progress in developing a smartphone app to measure CDOM.

November 2018:

The Minnesota Lake Clarity Browser ( with seven statewide classifications of lake clarity from 1975–2008 has been converted to ArcGIS Server with improved capability for search and display, additional basemaps, and data download. New classifications for 2010 and 2015 are underway and will be added as soon as they are available, along with capability to display temporal trends, geographic patterns and statistics by watershed, ecoregion and county.

Ray Hozalski presented a paper in mid-September on our CDOM work at the 19th conference of the International Humic Substances Society in Albena, Bulgaria.

Noah Germolus began his PhD studies in the joint MIT-Woods Hole Oceanographic Institute in Cambridge, MA, in September, 2018.

Leif Olmanson participated in an invitation-only workshop “A new paradigm in lake and reservoir research and management through global monitoring, modeling, and engaging and empowering people networks” in Alexandria, VA, Sept. 5-7, 2018. The workshop was sponsored by the Global Lake Ecological Observatory Network (GLEON); U.S. Geological Survey; UMN Dept. of Computer Science and Engineering; Center for Limnology, University of Wisconsin-Madison; and Cary Institute of Ecosystem Studies.

Leif Olmanson and Ben Page presented seminars "Near Real-Time System to Provide Critical Water Quality Information for Lake Management" to interest groups at the Minnesota Supercomputing Institute in August and April, 2018.

Jeff Peterson and Leif Olmanson  were awarded a two-year grant starting July 1, 2018, from the Minnesota Environmental and Natural Resources Trust fund, as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR), to build a near real-time water quality monitoring system using satellite imagery. The new work is a collaborative effort of the Remote Sensing and Geospatial Analysis Laboratory (RSGAL), Minnesota Supercomputing Institute (MSI), and the Water Resources Center (WRC).

Noah Germolus, an undergraduate research assistant on the NSF CDOM study, completed his B.S. in Environmental Engineering with highest honors in May and continued to work on the citizen-science component of the study during summer. Noah completed an honors thesis under the direction of Professor Ray Hozalski and Professor Emeritus Patrick Brezonik on “Trends in Colored Organic Matter and River Flow in the Mississippi River 1944-2010” using a 66-year record of daily color measurements from the Minneapolis water utility.” Germolus and his former advisors currently are preparing a manuscript for journal publication based on his analysis.

Claire Griffin presented invited seminars related to our remote sensing studies at the Southwest Research Institute (San Antonio, May 9, 2018), the Kansas Biological Survey (Lawrence, KS, April 20, 2018), and the University of Minnesota Duluth Dept. of Chemistry (Feb. 23, 2018).

Benjamin Page was appointed as a research fellow in the WRC in March 2018 as part of the new Digital Water Initiative, which is a joint effort of the WRC and MSI, and has joined our research group. Page was hired to work with Leif Olmanson (RSGAL) and David Porter (MSI) on WRC-housed grants related to remote sensing and mapping of lake water quality and ice phenology. Page has a strong background in geospatial analysis and remote sensing of inland waters. After earning a B.S. in biology from UMD, he completed an M.S. at the University of Georgia in geography, where he developed algorithms for atmospheric correction and satellite techniques to assess cyanobacteria bloom phenology. He also worked on geospatial data projects for NASA's DEVELOP and SERVIR programs, with a recent focus on remote sensing to monitor inland water quality with applications to the African Great Lakes.

November 2017:

Leif Olmanson was interviewed on Monitoring Minnesota lakes with Landsat Data for the USGS Landsat in Action video series.

September 2017:

leifseptResearch Associate Leif Olmanson (P.I.) has received a new two-year contract from the Minnesota Pollution Control Agency that will map lake water clarity statewide for two periods: 2010 and 2015. The project will enable updating our semi-decadal database that currently contains satellite-based water clarity results (reported as Secchi depth) for more than 10,000 Minnesota lakes in each of seven periods starting in 1975. The new grant also provides funds to update the LakeBrowser that is used to access the water clarity data.

This past summer was a very active time for our group gathering field data and water samples to calibrate statewide imagery for CDOM, chlorophyll, suspended solids, turbidity, and Secchi depth for our NSF and LCCMR projects. The 2017 field program was designed to collect samples within a few days following acquisitions of clear imagery by Sentinel-2.

sept2 We sampled 230 sites, from Hayes Lake in northwestern Minnesota and many lakes near Ely, MN to lakes within miles of the Iowa border. Claire Griffin, postdoctoral associate, led field coordination and sampling efforts with help from field teams that included three undergraduates, three technicians (recent graduates), two graduate students, and several Co-PIs. We also collaborated with researchers in the Cotner Lab at UMN, Lesley Knoll at the Itasca Biological Station, the Red Lake Nation DNR, Minneapolis Parks Board, Minnesota Science Museum St. Croix Research Lab, and volunteers from Brainerd and Lake Vermillion, who helped us obtain samples across a much larger area than we would have been able to do alone – many thanks to them! Despite cloudy conditions early in the summer, imagery from August and September provides clear data to map chlorophyll-a, suspended solids, and CDOM across the state. Some photos from the summer field work. 

August 2017:

rayhozalskiProfessor Ray Hozalski (Department of Civil, Environmental, and Geo-Engineering), an international expert on drinking water treatment processes and P.I. of our NSF grant on CDOM, gave an invited talk titled “Remote Sensing for Source Water Characterization” at a Gordon Conference on Drinking Water Disinfection Byproducts in early August. The week-long conference was held at Mount Holyoke College in South Hadley, Massachusetts, and the talk covered a broad range of topics involved in the NSF grant. According to Prof. Hozalski, the presentation was received enthusiastically by conference participants.




October 2016:

octoberOur ongoing work on satellite-based measurement of colored dissolved organic matter (CDOM) was described on NASA’s, Earth Observatory website, on October 25, 2016, in an article titled Minnesota: Land of the Many-Colored Lakes. The article provides maps of colored lakes in northern Minnesota and describes the state as “Minnesota, the land of 10,000 lakes,” might as well be called the “land of 10,000 shades of lakes,” stating that “many of them owe their color to CDOM: colored dissolved organic matter.” Comments by Leif Olmanson and Patrick Brezonik are included in the article, which can be viewed at:


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