Monitoring of the Rivers Glomma, Vorma and Lake Øyeren, SE Norway 2014

Summary

During the autumn 2014 macroinvertebrates, benthic algae and water quality were assessed at 5 sites in River Glomma, one site in River Vorma and at one site in Lake Øyeren. The average phosphorus concentration in Øyeren in 2014 was 7.8 μgP/l, classifying the lake to be at very good ecological status, according to the Water Framework Directive criteria. The average concentration of chlorophyll a in the production period was 4.1μg/l classifying the lake to very good ecological status. The upper part of River Glomma is polluted by copper (average 4.88 μg/l), probably caused by runoff from abandoned mines. The benthic algae at the uppermost sites of the river indicated very good ecological status with respect to eutrophication. The ecological status was reduced downstream. The ecological status according to benthic algae in River Vorma was good. The ecological status according to benthic macroinvertebrates was very good at the uppermost sites with respect to organic load and eutrophication, however it was reduced to good status further downstream. In Vorma the ecological status according the macroinvertebrates was good. On the average the ecological status measured by macroinvertebrates and benthic algae was fairly in accordance with each other, even though there was a tendency for lower status as measured by macroinvertebrates.