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Predicting Water Clarity of Lakes via Satellite

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Remote sensing is a method of gathering information about the physical world from photographs taken by LANDSAT satellites. The study, commissioned by MCWD and carried out by University of Minnesota Researchers Marvin Bauer and Leif Olmanson, compiled over 30 years of water quality data for 300 lakes in the MCWD.

The study uses an analytical model, based on actual water clarity measurements from hundreds of lakes throughout Minnesota, to predict water clarity base d on optical properties of satellite images. The model confidently predicts water clarity in lakes as small as 10 acres in size using images from 1973 and 1976, and as small as 5 acres in size using 1991-2004 images. This is because recent satellites offer improved spectral resolution. To read more about the study see the article 'Satellites expand lake monitoring reach' on Page 3 of the Winter 2006 edition of WaterPro.

Scroll down to see images depicting water quality from 10 points in time between 1973 and 2004. 'SDT' stands for 'Secchi Disk Transparency,' which is a measure of water clarity. The larger values (depicted in blue) represent clearer water, while lower values (red) represent more turbid water bodies. 'TSI' stands for 'Trophic State Index,' a measure of a lake's productivity (more productive lakes are less clear). Please note: the information presented on this page does not represent actual water quality samples. For smaller lakes, the chances for errors in the model's prediction of actual water quality increases. 

Water Clarity Legend

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Water Clarity Legend

July 3, 1973

Lake Minnetonka Water Clarity 1973

July 29, 1975

Lake Minnetonka Water Clarity July 1975

August 7, 1975

Lake Minnetonka Water Clarity August 1975

September 6, 1976

Lake Minnetonka Water Clarity 1976

September 4, 1991

Lake Minnetonka Water Clarity 1991

July 29, 1995

Lake Minnetonka Water Clarity 1995

September 12, 2000

Lake Minnetonka Water Clarity 2000

August 30, 2001

Lake Minnetonka Water Clarity 2001

September 5, 2003

Lake Minnetonka Water Clarity 2003

August 30, 2004

Lake Minnetonka Water Clarity 2004

separate, similar project, featuring Lake Minnetonka (PDF) was conducted by Patrick L Brezonik, Leif G. Olmanson, Marvin E. Bauer and Steven M. Kloiber.