There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of invertebrates, angiosperms and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail.
To determine this, various factors are taken into account, including biological aspects like the number and types of invertebrates, angiosperms, and fish. Additionally, chemical analysis is conducted to compare concentrations against established safe limits, resulting in either a "good" or "fail" rating.