—
2
—
2
The Trophic State Index (TSI) Calculator computes Carlson's Trophic State Index from Secchi disk depth measurements. TSI classifies lakes and reservoirs into trophic categories: oligotrophic (clear, nutrient-poor), mesotrophic (intermediate), and eutrophic (turbid, nutrient-rich). It is the most widely used lake classification system in limnology.
Secchi depth measures water transparency by recording the depth at which a black-and-white disk disappears from view. Lower Secchi depth means more turbid water and higher productivity. TSI converts this simple measurement into a standardized index for comparing lakes worldwide.
Carlson's TSI based on Secchi depth is calculated as:
TSI = 60 - 14.41 × ln(Secchi Depth)
Where:
Classification:
Inputs
Results
TSI = 60 - 14.41 x ln(3) = 60 - 15.83 = 44.2. This mesotrophic lake has moderate clarity and productivity.
Inputs
Results
TSI = 60 - 14.41 x ln(0.8) = 60 - (-3.21) = 63.2. This eutrophic water body likely experiences algal blooms.
Carlson's TSI is a standardized index developed by Robert Carlson in 1977 to classify lake trophic status. It can be calculated from Secchi depth, total phosphorus, or chlorophyll-a. The three forms are designed to give similar values for the same lake, allowing cross-comparison when only one measurement is available.
A Secchi disk is a simple circular disk (usually 20 cm diameter) divided into alternating black and white quadrants. It is lowered into the water on a graduated line until it disappears from view. The depth at which it vanishes is the Secchi depth, a measure of water transparency.
High TSI values indicate eutrophic conditions caused by excess nutrients (mainly phosphorus and nitrogen) from agricultural runoff, sewage, and urban stormwater. These nutrients fuel algal growth, reducing water clarity. Eutrophication can lead to algal blooms, oxygen depletion, and fish kills.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
How helpful was this calculator?
Be the first to rate!
