Remote sensing and water Clarity

*Click on any red text to view a detailed definition or description.

Since 1999, Citizen Lake Monitoring volunteers have assisted in a collaborative research effort with University of Wisconsin Environmental Remote Sensing Center by taking secchi readings on dates when the satellites were overhead. The volunteers' participation has allowed the University to successfully calibrate computer programs that enable satellite imagery to be used to predict Secchi Disc Depth and other water quality parameters on lakes. The researchers at the Remote Sensing Center are continuing their research. The ultimate goal is to put the satellite data into everyday use by making the water clarity data derived from the satellite imagery available to the DNR and to the public.

About Water Clarity and Trophic State

Clarity is a common, but indirect, way to roughly estimate the trophic or nutritional condition of the lake. Researchers use various methods to calculate the trophic state of lakes. Common characteristics used in combination to make the determination are:

• Secchi disk readings: an indicator of water clarity
• Chlorophyll-a: the amount of algae present
• Total phosphorus concentration: important for algae growth

Here is a link to Green Lake's clarity and trophic state from 1999-2001. The following information was gathered from www.lakesat.org.

	Legend - Clearer lakes have smaller trophics state indexes and larger secchi depths.

Lakes can be divided into four general categories based on trophic state: hypereutrophic, eutrophic, mesotrophic, and oligotrophic. These categories reflect a lake's nutrient and clarity level as in the chart below. Compare the above trophic state index with the chart below.

The University of Wisconsin Environmental Remote Sensing Center, in conjunction with the WI DNR, are currently analyzing water quality data from 2002-present to determine water quality trends. This information will be available in spring 2012.

Aerial remote sensing photos coming soon!