RIIM is a highly specialised course which trains people to do surveys of the invertebrates in their rivers. Such surveys can be a major step forward in identifying the source of trouble with river invertebrate abundance: not only do they indicate shortfalls in abundance, they can often show what may be causing it and point the way to a solution. The system allows you to monitor water quality by identifying freshwater invertebrates to species level.
The full circular can be found here