Alwen Reservoir, near Denbigh

What's here

Please be aware of timber haulage lorries using the forest roads whilst harvesting operations are carried out. Please follow all signage and instructions.


The first thing you notice on arriving at the Alwen car park is the huge dam which sits astride the reservoir.

The dam is the starting point for a seven mile trail around Alwen reservoir that can be followed by walkers and cyclists.

The trail goes through forest and moorland and there are far-reaching views over the reservoir.

The reservoir and dam were constructed in the early 20th century to provide water for the port of Birkenhead.

The conifer forests around the reservoir form part of Hiraethog Forest and were planted to replenish timber supplies following the First World War.

Cyclists and walkers can also follow a link route from Alwen reservoir to nearby Llyn Brenig where there is a visitor centre with café and toilets.

Walking trail

The walking trail is waymarked from start to finish.

Look out for the information panel at the start of the trail.

Find out about walking trail grades.

Alwen Trail

  • Grade: Moderate
  • Distance: 6¾ miles/10.9 kilometres
  • Trail information: The walking trail starts from the Alwen car park. It is a shared use trail and may be used by walkers and cyclists. It must be followed clockwise on foot – look out for the waymarkers.

The Alwen Trail runs through forest, moorland and along the water’s edge on surfaced paths and forestry tracks.

Along the way there are ever-changing views across the reservoir and to the mountains of Snowdonia.

Illustrated panels at the side of the path explore the wildlife, culture and folk tales of this historic upland landscape.

Look out for wildlife ranging from hen harriers to black grouse, and cuckoos to crossbills - you may even be lucky enough to see a red squirrel or osprey.

Man and woman walking on Alwen Trail

Mountain bike trail

All our mountain bike trails are waymarked from start to finish and have been graded for difficulty.

At the start of the trail there is an information panel – please read this before setting off.

Alwen Trail

  • Grade: Blue (moderate)
  • Distance: 10.9 kilometres
  • Trail information: The mountain bike trail is waymarked and starts from the Alwen car park. It is a shared use trail and may be used by walkers and cyclists. It must be followed anti clockwise by bike – look out for the waymarkers.

The trail links forest roads with purpose built, often singletrack, trail sections weaving in and out of the forest around the reservoir.

It has great variety for such a short trail with some sheltered forest and open moorland.

The climb up from the bridge over the reservoir is taxing but can be pushed up.

The highpoint of the trail beyond the bridge is very exposed to the elements and you should be prepared for any change in weather.

This shared use trail must be followed anti clockwise by bike – look out for the waymarkers and please give way to walkers.

Llyn Brenig visitor centre

The entrance to Llyn Brenig car park is off the B4501, one mile from the entrance to the Natural Resources Wales Alwen car park.

The Llyn Brenig visitor centre is managed by Dŵr Cymru/Welsh Water.

It has a café, toilets, fishing shop, play area and bike hire.

The Brenig Trail (9½ miles/15 kilometres) sets off from the visitor centre car park and makes its way around Brenig reservoir – this trail can be followed by walkers and cyclists.

Cyclists and walkers can follow a link route between the car parks at Alwen Reservoir and Llyn Brenig.

The Llyn Brenig reservoir was constructed in the 1970s and it helps to regulate the water supply to the River Dee.

It is also one of the premier fly fisheries in the UK and it hosts international competitions.

Tickets for fishing in the Alwen and Brenig reservoirs are available from the visitor centre.

For more information see the Llyn Brenig website 

Man and child fishing at Llyn Brenig

Closures and diversions

  • Sometimes we need to close or divert trails for your safety whilst we undertake maintenance work or forest operations
  • Occasionally we may have to close a site in extreme weather, such as high winds or snow and ice due to the risk of injury to visitors or staff
  • Please always follow any instructions onsite and make sure you follow any temporary diversion signs in place

How to get here


Alwen is 11 miles south west of Denbigh.

This site straddles the county borders of Conwy and Denbighshire.

Ordnance Survey map

Alwen is on Ordnance Survey (OS) map 264.

The OS grid reference for the car park is SH 956 529.


From the south: take the B4501 from Cerrigydrudion towards Denbigh, following the brown and white signs to Llyn Brenig. After three miles, turn left down a stoned track to the Alwen Natural Resources Wales car park.

From the north: Take the B4501 from Denbigh towards Cerrigydrudion. After 10 miles, go past the Llyn Brenig Dŵr Cymru/Welsh Water visitor centre car park and continue for one mile. The turning to Alwen Reservoir is on the right and the car park is at the end of a stoned track.

Public transport

The nearest train station is in Rhyl.

For details of public transport visit the Traveline Cymru website.


The car park at Alwen Reservoir is operated by Dŵr Cymru/Welsh Water.

The parking charge is £2.50.

You need to pay the parking charge with the correct cash as the machine does not give change.

Contact details

There are no staff at this location.

Contact our customer team for general enquiries during office hours, Monday to Friday.

Related document downloads

Alwen - Brenig leaflet PDF [6.0 MB]
Alwen trails information PDF [806.2 KB]
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