Penllergare Valley Woods

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What are we doing at the Upper Lake 2014

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We’re completing the work started last year to dig out the silt and spread it on the old park area down the valley. We’re also finishing off the earthworks around the turbine site. The lakeside track is closed while dump trucks are carrying silt away. The waterfall will stop flowing when the lake is drained down and the river pumped around the lake. Depending on the weather, this work is due to be completed by the end of September. We regret any inconvenience caused. We hope that you will take the opportunity to explore other paths and tracks available – there are nearly 7 miles of paths and tracks altogether.

What's going on01

Why are we doing this?
The lake is being reinstated to its historic form and to prevent total reversion to marshland and woodland, as part of the first stage to restore the historic landscape design:

Penllergare Valley Woods is notable as a partial survival of a very important picturesque and Romantic landscape of the mid-nineteenth century created by John Dillwyn Llewelyn, a nationally important figure in horticulture. Despite the neglect of recent decades, the well watered and wooded landscape still retains the original designed qualities of magnificence, surprise, beauty and seclusion. (Conservation Management Plan, 2008)

The upper lake, or fish pond as it was described in some old maps, was made by damming the river Llan in the 1840s. The dam, made of stone quarried in the valley, was carefully designed to mimic the natural rock strata. The falls have three channels over which the river falls in picturesque and sometimes spectacular style. The falls are one of the striking historic features of the estate.

By 1936, the lake had almost completely silted up and disappeared and was shown on maps as marshland. A partial restoration was carried out in the 1980s, but we believe that this is the first time that a full scale restoration has been attempted.

Upper Lake - Summer Evening.

Upper Lake – Summer Evening.

What is silt and why does the lake silt up?
Silt is an earthy material made up of fine sand, clay and other matter that has been washed off the land and into our streams, rivers and lakes. It is carried by fast flowing water, especially in flood conditions, and drops out of the water when the flow slows, eg as it enters the lake. Silt is generally rich in nutrients. It clogs up ditches, streams, ponds and lakes and if not cleaned out, the lake would revert to woodland with the loss of the most important feature of the historic landscape design.

How is the lake being de-silted / dredged?
The flow of the river is being diverted by pumping it around the lake. This will allow the silt to be worked in a drier state and to make it easier to dig out and cart it to the former park area. It is estimated that there were 16,000m3 of silt to be removed. Half was dug out in 2013 and the rest will be removed in July, August and September.

Why do it during the summer months when most people are visiting?
Because these are usually the driest months of the year, making the job easier and less disruptive for the Valley as a whole. Also, from October to April, the river is used by salmon and trout to breed and so no work in the river is allowed during this time. February to June is the height of the bird nesting and wildlife breeding season. So a reasonable time has been left to allow nesting birds to fledge their young.

Will any wildlife be harmed?
Fish and other aquatic creatures in the lake will be captured and released into the river below the dam before the lake is drained down. Most birds, frogs and toads will move out of the way of the works. Some silt is to be retained on the eastern side of the lake to encourage a greater diversity of wildlife. The wildlife in this retained silt will help to rapidly recolonise the lake. In addition to re-creating a stunning landscape feature, the restored lake will support a greater variety of wildlife than at present.

Will the waterfall and Llewelyn Bridge still be accessible?
Yes – Two crossing points have been agreed – one at the M4 culvert, to retain access between the car park and the east side of the valley. The other is at the bottom of the new path from the terraces – giving access to the waterfall and on to the Llewelyn bridge and beyond.

Where is the best and safest place to watch the contractors in action?
From the east bank, the carriage drive, the terraces or the top of the waterfall.

How deep is the lake?
It is about 20ft deep nearest to the dam (waterfall) and then getting shallower towards the top end.

Will fishing be allowed in the lake?
We have no plans to encourage fishing in the lake.

How many islands will there be?
There were originally three or more islands. However in order to minimise the accumulation of silt in future, it was decided to retain only one.

How can I find out more or get involved?

  • Come and see the work in progress, have a chat with a member of the Penllergare team and enjoy a cup of ‘real’ coffee and some locally made cake or a cream tea in our volunteer run coffee shop.
  • Sign up to become a volunteer
  • Sign up to become a subscribing member of the Friends of Penllergare Valley Woods
  • Join David our site manager for a tour of the restoration project on the last Wednesday of every month throughout the Summer at 6pm. Meet at the new Penllergare Car Park. Wear sturdy footwear.
  • Sign up for our free monthly bulletin

For more information, please contact the Penllergare Trust at or tel 01792 344224 or visit

The Penllergare Trust is a charity dedicated to preserving Penllergare Valley Woods for everyone to enjoy. Please support us today by donating, volunteering or becoming a Friend.


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