At the time that the NRWQN was developed, the incorporation of benthic (river bed) biological monitoring was considered quite innovative.
The network sampling includes two biological measures of water quality. These biological indicators provide a direct measure of response to changes in water quality.
Periphyton (algae attached to the river bed), can sometimes be a nuisance, and its cover at each site is visually assessed on monthly visits.
Benthic macroinvertebrates are sampled annually from the river bed at suitable sites, using a Surber sampler in late summer. The types of invertebrates present (e.g., mayflies versus snails) provide an ‘integrating’ index of river ecological ‘health’.
Benthic biological data from the NRWQN has been used for a wide range of applications. This includes SoE reporting, practical water management and scientific applications.