The Afon Clywedog is an upland headwater tributary of the

River Severn The River Severn (, ), at long, is the longest river in Great Britain. It is also the river with the most voluminous flow of water by far in all of England and Wales, with an average flow rate of at Apperley, Gloucestershire. It rises in t ...

Powys Powys ( , ) is a Principal areas of Wales, county and Preserved counties of Wales, preserved county in Wales. It borders Gwynedd, Denbighshire, and Wrexham County Borough, Wrexham to the north; the English Ceremonial counties of England, ceremo ...

, Wales. It is approximately long and has its source on the flanks of

Plynlimon Plynlimon, or Pumlumon in Welsh language, Welsh (also historically anglicised as Plinlimon, Plynlymmon or Plinlimmon), is the highest point of the Cambrian Mountains in Wales (taking a restricted definition of the Cambrian Mountains, ex ...

and has its confluence with the Severn in

Llanidloes Llanidloes () is a town and community on the A470 and B4518 roads in Powys, within the historic county boundaries of Montgomeryshire (), Wales. The population in 2011 was 2,929, of whom 15% could speak Welsh. It is the third largest settleme ...

. The annual rainfall over the catchment is between and .

River regulation

A large part of the upper catchment of the river is inundated by the Clywedog reservoir which stores water from the catchment, especially during the winter months, and releases it during periods of low flow to support the flow in the Severn so that drinking water may be abstracted downstream. The management rules also enable the reservoir to maintain the reservoir below maximum level during the winter so that there is capacity to absorb

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

flows to reduce the impact of flooding further down the main river.Hydrology in Practice. Shaw E
/ref> The Afon Clywedog thus has a highly regulated flow with relatively high flow in dry conditions and reduced flow in wetter weather.

References

External links

{{authority control River regulation in Powys Clywedog Clywedog 1Clywedog

River regulation

See also

References

External links