July 17, 2012 Water Monitoring Report

At the Fox River Inlet the Secchi disk was visible while sitting on the bottom,
so true clarity could not be determined.

 Out of concern for oxygen and temperature levels during the recent fish kill, today I expanded water quality monitoring and reporting to include dissolved oxygen (D.O.) at each station.  I also did temperature and D.O. profiles to see how these factors change with depth.  While conditions are not as extreme as before they are a good indicator of how the lake responds to high temperatures.

Temperature depth profiles in the East and West Basin show that, as expected temperature does not change significantly with depth as with nearly all shallow lakes and reservoirs  Slightly higher temperatures in the West Basin were because they were taken slightly later in the day. 

D.O. concentrations at 1.5 feet were very good throughout the sample sites.  The D.O. depth profile however indicates how fast D.O levels begin to drop off in deeper water.  The primary reason for this is low water clarity.  As over abundant algae get mixed in the water column down below were little light penetrates they stop producing surplus oxygen, and begin extracting it from the water, just like the fish, invertebrates and zooplankton surrounding them.  Also the deeper the water, the further it is from the surface where oxygen can be exchanged with the atmosphere.  Still D.O. levels at the bottom are not harmful to fish, but oxygen is becoming limited.   Conversely he Fox River Deep Hole upsteam of Puckaway had a clarity of 7.75 feet and had a D.O. of 7.38 mg/L at 1.5 ft and 7.52 mg/L at 7 feet.  Clearer water has less algae.

An important note on D.O.:  After the sun goes done all algae and aquatic plants begin using oxygen found in the water.  If they are over abundant D.O. levels can sometimes become dangerously low.  D.O. levels have not been tested at night.  

D.O. at a depth of 1.5 feet

Clarity today hit a new low since monitoring began with only 6 inches of clarity exiting Lake Puckaway, while the lake took in 93 inches of clear water from the Fox River.  In other words the lake made the water 15.5 times less clear. 

Right to Left: Water as it moves The Fox River into Lake Puckaway and out again.
Stations match up with water clarity graph at top of post.