Secchi Depth Chart

Water transparency is measured with a black and white disk called a Secchi disk. The Secchi disk is lowered into the water until it cannot be seen. The depth at which it is no longer visible is called the Secchi depth. The water transparency, or Secchi depth, is dependent on the density of suspended materials in the water. The chart below shows the average Secchi Depth for all observations between 1990 and 2007. The plot provides a general indication of the ranking of Secchi Depth in area lakes. Observe that the largest Secchi Depth of just over 19 feet occurred in Big Glen Lake. The smallest Secchi Depth occurred Little Glen Lake. This lake also had the highest total phosphorus concentration as shown on the Total Phosphorus Chart. The Secchi Depth of about 7.5 feet means that a six foot person standing in Little Glen Lake up to their nose in water will just be able to see their toes. Finally despite the significant variation among the various lakes, the Secchi Depths are high compared to many other lakes in the State and are currently indicative of high water quality conditions. Continued vigilance and careful and thoughtful planning are essential to maintaining these desired conditions.