This page shows results of a study that uses remote sensing to estimate water quality. 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 based 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.

For more information, please contact MCWD's Water Quality Staff.

Click here to read about a separate, similar project, featuring Lake Minnetonka, conducted by the North American Lake Management Society.

 

                                                              July 3, 1973

                

                                                              July 29, 1975

                                                              

                                                              August 7, 1975

                                                              September 6, 1976

                                                              September 4, 1991

                                                              July 29, 1995

                                                              September 12, 2000

                                                              August 30, 2001

                                                              September 5, 2003

                                                              August 30, 2004