The Mournebeg runs along the border at Derrygoonan and Lisnacloone and eventually flows into the Derg between Aghyaran and Castlederg.
The Environmental Protection Agency (EPA), in its 2020 Water Quality indicators report, found that over 2017-20 only the Mournebeg and an unnamed stream labelled Ara_20 in Tipperary were in bad condition.
According to the EPA: “The biological quality of river water bodies across the country is assessed as part of the National Water Framework Directive monitoring programme. The system assesses macroinvertebrate communities to categorise the biological quality value of a river into five classes: high, good, moderate, poor and bad.”
Macroinvertebrates are tiny animals without backbones like snails, worms and insects.
Last November both the Mournebeg and the Derg were affected by a massive peat slide at Meenbog in Donegal. Tonnes of peat were swept into the rivers which form part of the Foyle system. This is not mentioned in the EPA report occurring as it did late in the recording period.
The EPA instead see high nutrient levels, such as phosphorus and nitrogen, as the main threat to water quality. Almost half of rivers (47%), a quarter of groundwaters (24%) and one fifth of estuarine and coastal water bodies (21%) have nitrogen levels that are too high. The levels impact the ability of these waters to sustain healthy ecosystems and cause nuisance algal blooms in estuaries. High nitrogen levels, above the drinking water standard, can also pose a risk to human health, the agency says.
EPA Director of Evidence and Assessment, Dr Eimear Cotter said: “If we do not substantially reduce nitrogen inputs to our rivers, and ultimately our marine environment, we are in danger of further deteriorations in water quality and losing our excellent coastal water quality.”