Completed in 1926, Llwyn Onn is the southernmost and largest of the three reservoirs built across the Taf Fawr to supply water to Merthyr Tydfil and the valleys south to Cardiff. With unsually warm and dry weather so far in 2010, water levels at Llwyn Onn have dropped dramatically, revealing Pont-yr-Daf and allowing safe access along the retaining wall to the sluice gates at the southern end.
The Taff Trail (national cycle route 8 ) runs down the western edge of the reservoir, and from the road there are plenty of paths like this one that you can use to walk down to the shores of the reservoir.
When the reservoir is at normal levels, Pont-yr-Daf lies underwater. But current water levels have fallen low enough to reveal the bridge – the only surviving structure from when the reservoir was created. This shot is looking north … note how the whole northern end of the reservoir is both silted up and completely dried out.
Another shot of Pont-yr-Daf, showing the low water levels as we look south down the reservoir.
On reflection, I should have taken this photo at f/8, and made it sharp front-to-back. A lesson for future shots, I think.
Here’s a pile of human junk out in the middle of the drying Llwyn-Onn reservoir.
Note how green the ground is starting to turn at this spot. My wife reckons the ground here could have been exposed for about a month for these plants to take hold like this.
The Llwyn-Onn reservoir is completely dry north of Pont-yr-Daf. From the bridge itself, you can clearly see how the water is retreating south towards the reservoir’s retaining wall.
This is a close-up shot of a tree that had been washed up in the reservoir at some point.
The water levels at the Llwyn Onn Reservoir north of Merthyr Tydfil have fallen quite low this year, exposing all of the northern end of the reservoir bed. It is drying and cracking up quite nicely.
As the water level drops, the reservoir bed is being slowly uncovered. At first, the bed is a horrible sticky mud, and until it dries out it’s a bit tricky to walk on. The local fishermen have solved this problem, by creating stone pathways out to the water and extending them as the water level continues to drop.
Here’s a shot of the reservoir retaining wall, looking south along the reservoir towards Merthyr. You can clearly see how far the water stocks have fallen already this year, and summer is only just beginning.
At the top of the retaining wall, my wife spotted this tree growing out of a drainpipe. It certainly looks like it has been here for some time.
With the water levels so low, we were able to carefully walk out along the reservoir wall to the sluice gates.
To stop debris being flushed into the sluice gates (and, presumably, to stop nosey photographers from doing something silly and ending up falling down the gates!) there are these metal bars across all of the sluice gates at the reservoir.
View this photo at ‘large’ or better on Flickr … the rust patterns in the bars are quite something.
Behind the bars lie the sluice gate itself … but what does it look like and where does it go?
This is what the bars are protecting … one of the sluice gates at the reservoir. Not far into the blackness there must be quite a drop down to the valley floor below. We didn’t go and explore the other side, so I couldn’t tell you whether the gates empty into the river below or into the water plant. Either way, it’s a ride that you don’t want to try.
Whilst clambering back along the reservoir wall after visiting the sluice gates, I spotted this shoe further down towards the receding water. I’m guessing it was washed up here when the water level fell, rather than being simply abandoned by someone else scrambling along the wall.
- Trelewis’s photos of Pont-yr-Daf; it was her shots on Flickr that convinced us to head up to the reservoir to see the bridge for ourselves!
- Alan George’s Cwmtaff page, including photos of the buildings lost when the valley was flooded to create the reservoir.
- brackenb’s photos of Pont-yr-Daf, including a shot in the comments from 1959.
- A list of the UK’s reservoirs on Wikipedia.