The Alberta Index
The Alberta index uses a ‘performance indicator’ for water quality, which essentially computes the fraction of samples which do not comply with water-quality standards from among the total sampled.
Uses and Limitation:
The designated uses of this index include water quality estimation for recreation, agriculture and aquatic life.
The index can give meaningful results only if a statistically significant number of samples (>30) are taken randomly from a site. With progressive lesser number of samples, it may give increasingly biased results.
Standards Required
Any national or international water quality standards could be used in this method.
Calculation of Alberta Index
\(\)
\begin{eqnarray*}
A = \frac{n_{exceed}}{n_{measure}} X 100
\end{eqnarray*}
A is, therefore, the percentage of the samples, taken at a site where one or more of the variables exceed the objectives for a designated use.