This page was last modified on Monday, April 28, 2008 03:15:35 PM 

 

 

 

 

 

 

We participate in two statewide water quality programs. One is Riverwatch and the other is the Clean Lakes Program.

 

 

 

 

We use water quality kits from the DNR Riverwatch program. At the Riverwatch website you can also see the Barbee Chain water quality history. Just select 'search database', specify the Tippecanoe watershed, and the specific locations (Grassy Creek (two locations) and Putney Ditch.

In addition we participate an Indiana University program called Clean Lakes Program.

 

We use the Sechii Disk and measure clarity every several weeks. The results are entered into a statewide database on the Clean Lakes Program website. Historical results for many Indiana lakes can be viewed from this site. 

 

The clarity data for 2006 in the Barbee chain shows the following

 

 

Clarity in the lakes goes through a number of cycles for a number of reasons. Plankton biomass tends to be highest when water is well-mixed throughout the lake (lake turnover). In temperate lakes, there are two periods of lake mixing or lake turnover, one just following ice melt (early spring) and one in the fall (around September). In the winter, the lake is stratified with colder water sitting above warmer water. In very productive lakes especially, the lower (warmer) layer might have very low levels of dissolved oxygen, since decomposition of organic matter (which consumes oxygen) can persist even in low temperatures. This also means though that the lower layer has more nutrients than the upper layer. Because the water column is thermally stratified, the upper and lower layers cannot mix until air temperatures become warmer. In early spring, warmer air temperatures lead to an increase in the temperature of the lake’s surface layer. The upper layer thus becomes closer in temperature to the lower layer, and the two layers can mix. Nutrients from the bottom can thus mix with oxygen from the surface, leading to an increase in plankton (especially diatom) biomass (and a decrease in Secchi transparency) right after ice melt. Water circulation can also resuspend particles that had settled to the bottom during stratification, which can also contribute to decreased Secchi transparency in early spring.

In early summer (beginning around May), lakes go through a “clearwater” phase, in which the algal populations that prospered in early spring begin to die. Plankton that were successful in early spring (adapted to colder spring temperatures) may die as a result of increased temperature in early summer. In addition, May marks the onset of summer stratification. In this case, the upper water layer is warmer and sits above a colder water layer. Again, the upper water layer has fewer nutrients than the lower layer (because decomposition occurs in the sediments, not at the surface), and the lower layer will have less oxygen than the upper layer (because of oxygen-demanding decomposition in the sediments). Once again, since the two layers cannot mix due to temperature differences, plankton at the surface face a shortage of nutrients in early summer, and thus die. Too much light in early summer can also inhibit plankton growth (a process called photoinhibition). Finally, zooplankton biomass increases in early summer, and since zooplankton feed on phytoplankton, phytoplankton populations decrease even further in early summer. All these factors lead to the death of plankton in early summer. The water thus becomes very clear as plankton die and settle to the bottom. Also, since the lake is now in summer stratification, particles from the sediments cannot become resuspended in the upper water layer. Thus, Secchi transparency increases in early summer (April-May).

In later summer (June-August) temperate lakes are often dominated by Cyanobacteria, which are adapted to survive under conditions of low nutrient availability, high temperatures, and water column stability. Plankton biomass and Secchi transparency is often at intermediate levels during this part of the summer.

 
Finally, in the fall (around August/September), air temperatures decrease and thus decrease the temperature of the upper water level in the lake. Again, the temperature of the upper layer approaches the temperature of the lower layer, and the two layers can mix. Oxygen from the surface meets nutrients from the bottom, causing plankton to grow and multiply. Secchi transparencies are therefore low during this period. Again, suspended particles during lake turnover can also play a role in decreased Secchi depth in the fall.