River Dee/Glyde
The Rivers Dee and Glyde are the principal rivers in this catchment. They join close to Annagassan before discharging into Dundalk Bay. The River Dee rises near Bailieboro in Co. Cavan and flows in a north-easterly direction for over 50 km through counties Meath and Louth before entering the sea at Annagassan. The River Glyde owes its origins to a series of smaller tributaries, which rise in counties Cavan and Monaghan. These include the Tubermannin and the Killany Rivers, which contain stocks of wild brown trout. The upper reaches of the Glyde are deep, slow-flowing and known as the Lagan River. The Lagan and Kilanny River meet at Tully, Co. Louth, to form the River Glyde. The River Glyde contains stocks of wild brown trout and salmon throughout.

The Rivers Dee and Glyde enter the sea into the Proposed Natural Heritage Area (pNHA) of Dundalk Bay, one of 24 proposed NHAs in the county. The rivers also support species designated under the EU Habitats Directive including: river lamprey, brook lamprey, sea lamprey, Atlantic salmon and white-clawed crayfish. The catchment also includes the Annex I priority habitat 'Alder Woodland on Floodplains', characterized by alluvial forests with alder (Alnus glutinosa) and ash (Fraxinus excelsior).

Invasive Plant Distribution in the Dee/Glyde catchment - 2011 update
Two of the four target invasive plant species were found on the Rivers Dee and Glyde: Giant Hogweed and Japanese Knotweed. Giant Hogweed’s distribution was contained within the lower stretches of both rivers, covering approximately 0.5 km of the River Glyde and 8 km of the River Dee. A large infestation of Japanese Knotweed was found in the Castlebellingham Estate on the River Glyde and various other small patches throughout the lower stretches of the rivers and at Rahan’s Lough near Kingscourt. No Himalayan Balsam has been recorded in this catchment to date.