Research Results and Applications

Key activities and results from Minnesota projects

1. Satellite Remote Sensing of Minnesota Land Cover and Impervious Surface Area

Conversion of rural landscapes to urban and suburban land uses is directly related to increasing amounts of impervious surface area. Imperviousness affects the amount of runoff to streams and lakes and is related water quality of surrounding lakes and streams, to urban heat island effects, habitat degradation and fragmentation, and aesthetics of landscapes.

The University of Minnesota’s Remote Sensing and Geospatial Analysis Laboratory has completed classifications of land cover and impervious surface area of the state for 1990, 2000, and 2013, and for 1986, 1991, 1998, 2002, 2007, and 2015 for the Twin Cities metro area. Classification of the Landsat Thematic Mapper data enables quantifying the spatial and temporal patterns of impervious surface area over large geographic areas at modest cost.

The classification data are available at rs.umn.edu

2. Satellite Monitoring of Minnesota Lake Clarity

Classification of lake clarity, a key indicator of water quality, using Landsat satellite imagery has proven to be an accurate and economical method to monitor the condition of lakes in Minnesota. The Remote Sensing and Geospatial Analysis Laboratory, with support from the Minnesota Pollution Control Agency and Legislative Commission on Minnesota Resources, has developed and extended the capability for using satellite remote sensing to classify the clarity of over 10,000 lakes at different times over the past 30 years.

Our research has documented a strong relationship between the spectral-radiometric responses of Landsat TM and ETM+ data and in-situ observations of water clarity (Secchi depth transparency). The relatively low cost, geographic coverage, spatial resolution, and availability of Landsat data make it particularly useful for assessment of inland lakes. The geographic coverage of 12,000 square miles per Landsat image allows for the simultaneous assessment of thousands of lakes in lake rich areas. The spatial resolution of 30 meters is suitable for all lakes down to about 10 acres and can be used to map in-lake variability.

Classifications at approximately five-year intervals over a 30-year period (1985, 1995, 1990, 2000, 2005 and 2008) provide an unprecedented assessment of lakes in terms of number of lakes and geographic and temporal extent. We are analyzing the data for temporal and geographic patterns and trends, as well as relationships to land use and other factors that may cause changes in lake quality. Initial analysis indicates relatively stable conditions statewide, but more meaningful analyses are now possible for individual lakes, as well as by county, lakeshed, watershed, and ecoregion. The data are being used by the MPCA and other agencies and citizens.

Data for all lakes and years are available in the LakeBrowser, a web-based mapping tool that enables searches and display of results for individual lakes at: water.rs.umn.edu.