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A collaboration of the University of Minnesota's Remote Sensing and Geospatial Analysis Laboratory and Water Resources Center

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Monitoring Lake Clarity

The Upper Midwest is characterized by tens of thousands of inland lakes, networks of rivers and streams, and an abundance of groundwater, soil moisture, and winter snow pack. Although this resource is plentiful, it is heavily utilized to support commerce, recreation, transportation, agriculture, and numerous industries. This heavy reliance of infrastructure and economy on the regional water resources translates into high vulnerability to potential changes in water quality.

Human activities are impacting the quality of water resources in many ways, with eutrophication being one of the most pervasive problems affecting the lakes in the Upper Great Lakes region. The primary cause of this "accelerated aging" of the lakes is excessive nutrient input from near-shore land use as well as urban and agricultural runoff. Understanding this tie between lake water quality and land use is a major focus for our research.

Protecting and monitoring lake water quality is a major concern for many local and state agencies. Organizations, like the Citizen Lake Monitoring Program, routinely measure physical, chemical and biological properties of the region's water resources. However, because of expense and time requirements for this ground-based monitoring, it is impractical to monitor more than a small fraction of this large resource by conventional field methods. The use of satellite remote sensing is a cost-effective way to gather the information needed for water quality assessments in lake-rich areas.

For effective environmental planning and management, it is vital to have long-term water quality information on a broad regional scale. Although it is not possible to go back in time and collect additional water quality information using conventional field methods, Landsat satellite data have been collected regularly since the early 1970s, allowing the possibility of extracting historical water quality information from archived images.

The extraction of historic and current water quality data from satellite images, coupled with existing data collection efforts facilitates the development of comprehensive regional databases that can be used to evaluate regional differences and water quality trends over time. If used along with land use data, this information can help determine the impacts different land use practices have on lake conditions.

Results of such analyses will help local and state agencies make informed decisions about development policy and improve the management of lake resources.

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