Usk Reservoir
The Usk Reservoir is located in the upper Usk Valley, at above sea level, in the western part of the Brecon Beacons National Park, Wales. The county boundary between Carmarthenshire and Powys runs through the reservoir which lies about six miles to the north of the Black Mountain escarpment. It is an important landmark for walkers on the mountain range. History. Completed in 1955 by Swansea City Council, the dam is approximately 100 ft (30m) in height and 1600 ft (480m) in width. It was the first example in the UK of an earth dam with  horizontal drainage blankets. The reservoir covers some of land. It can be located just off the minor road between Trecastle and Llanddeusant, west of Sennybridge. The reservoir is now owned by Welsh Water and the surrounding forests are managed on their behalf by Natural Resources Wales. Most of the area is open to walkers and cyclists via forest tracks and other footpaths. There are several small car parks for visitors. The reservoir is stocked with freshwater fish such as trout and can be fished with an appropriate licence.