• MicroSieman per centimeter of water measured at a temperature of 25 degrees Celcius (abbreviated ?S/cm @ 25? C); and
• Micromhos per centimeter (abbreviated micromhos/cm or ?mhos/cm)

The Role of Specific Conductance in Waterbodies
Specific conductance increases when more of any salt including the most common one, sodium chloride, is dissolved in water. For this reason, conductance is often used as an indirect measure of the salt concentration in waterbodies. In general, waters with more salts are the more productive ones, except, of course, where there are limiting nutrients or limiting environmental factors involved.

Natural factors can also cause higher conductance values in the open water. For example, drought conditions can increase the salt concentrations in a waterbody in two ways:

(1) drought can cause inflowing waters to have higher salt concentrations, and
(2) heat and low humidity can increase the rate of evaporation in open water, leaving the waterbody with a higher concentration of salt.

Because animal and human wastes (sewage, feed lot effluent, etc.) contain salts, the measurement of conductance can also be used for the detection of contamination. Since most discharges of industrial and municipal wastewater directly into lakes in Florida have been stopped, measurements of conductance are now used in this context primarily to detect septic tank seepage along shorelines. (It's important to keep in mind that elevated conductance measurements may have various causes and do not by themselves prove there is contamination from human or animal wastes.)

In Florida
Waterbodies in the Florida LAKEWATCH database have average conductance values that ranged from 11 to over 5500 ?S/cm @ 25? C. Over 75% of these waterbodies had conductance values less than 190 ?S/cm @ 25? C.

The location of a waterbody has a strong influence on its conductance. For example, lakes in the New Hope Ridge/Greenhead Slope lake region in northwestern Florida (in Washington, Bay, Calhoun, and Jackson counties) tend to have conductance values below 20 ?S/cm @ 25? C, while the lakes in the Winter Haven/Lake Henry Ridges lake region in central Florida (Polk County) tend to have values above 190 ?S/cm @ 25? C.

Health Concerns
There are no known human health concerns directly related to specific conductance. In waters where human or animal waste contamination is suspected, bacterial tests should be conducted regardless of whether conductivity values are high.