River Derreen

River Derreen
Footbridge over the Derreen River near Hacketstown
Native name	An Daoirín
Etymology	Diminutive of doire, Irish for grove, esp. oak
Country	Ireland
Cities	Hacketstown, Tullow
Basin features
Main source	Lugnaquilla, County Wicklow
River mouth	Irish Sea at Wexford via River Slaney
Basin size	201.18 km2 (77.68 sq mi)
Physical characteristics
Length	40 km (25 mi)

The River Derreen (Irish: An Daoirín) is a large river in the southeast of Ireland. It rises on central Lugnaquilla Mountain in the western Wicklow Mountains and flows south from Lugnaquilla Mountain and then southwest to join the River Slaney south of Tullow, passing close to Hacketstown and Tullow, Co. Carlow before it joins the Slaney upstream of Aghade bridge. Running through tillage and pastureland in its lower reaches, the Derreen with its sandy, gravelly bottom is a prime salmon spawning tributary of the Slaney. Passing through counties Wicklow and Carlow, it is the first large, major tributary of the River Slaney.

Towns on the Derreen include Hacketstown and Tullow. It is crossed mainly by old humpbacked stone bridges. It is a rural river, flowing through only 2 major towns.

Varied and plentiful wildlife can be found in the environs of the river. In Wicklow, herds of deer can be seen, as well as swans, dippers, wild ducks, herons and kingfishers. At dusk, bats, owls and otters may be seen, while the mudflats of the Slaney estuary are favoured by black-headed gulls, redshanks and oystercatchers. The rare goosander can be seen on the Slaney at Kildavin. The River Derreen holds occasional salmon in the spring but the upper reaches are better known for trout, averaging 0.5lbs. The best of the fishing is from March to June. It is primarily a Brown Trout fishery. In season, brown trout, salmon, sea trout and occasional pike are fished. There are two angling clubs with fishing rights on the Derreen River and the remainder is in private hands. It also a habitat of the freshwater pearl mussel.