It is similar to the trophic state index but was proposed as alternative that suited New Zealand.

The Trophic state index of the lake is Eutrophic.

Limnology classifies lakes (or other bodies of water) according to the trophic state index.

Trophic state index (water quality indicator for lakes)

The quantities of nitrogen, phosphorus, and other biologically useful nutrients are the primary determinants of a body of water's trophic state index (TSI).

Trophic state index - primary determinants of a body of water's trophic state index .

These levels are scientifically measured using the Trophic state index (TSI), and the chain of lakes should have TSI numbers of 60 or higher.

Both Lake Manapouri and Lake Te Anau lie within the ultra-oligotrophic index on the trophic state index with clear highly oxygenated waters of very low biological productivity.

Measurements taken at the time, that included the examination of Carlson's Trophic state index, the measure of Chlorophyll, inorganic nitrogen and phosphorus in the water column were made, showing increases in all measures.