Visitor's horror at state of Eryri's 'Lake of Beauty' and why there's no cause for alarm

A man revisiting his old haunts last weekend was disturbed to see the state of Wales’ largest natural lake. Water levels at Llyn Tegid - which travel writer George Borrow called “Lake of Beauty” - appeared to be dangerously low.

For answers, the former Bala resident turned to social media. “I was shocked to see how low the level of the lake was,” he said. “Memories of it lapping up to the wall by Loch Cafe.... today the landing stage is out of the water. No recent drought so why is it so low, as it detracts from the beauty of the lake?”

Lake levels can ebb and flow and over the centuries Llyn Tegid has suffered from the vagaries of the elements. At times the Eryri lake has flooded dangerously, whipped up by south-westerly winds and deluged by hillside run-off.

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In the 18th century, travellers warned the lake was vulnerable to “dreadful” overflowings: in the early 1780s a “prodigious” flood that killed several people was referred to by both Thomas Pennant and Richard Fenton. The later records coming across a “vast collection of large stones” from a turnpike swept away from the lake.

He added: “The Lake of Bala was covered with the wreck of different houses, and one person recovered two feather beds floating on the lake, and one with a looking glass on it as she had left it when she left her house.”

These days, Llyn Tegid’s waterline is determined not just local factors but also by sophisticated computers taking their cues from elsewhere. The Eryri lake is a key cog in a vast water regulation network that has its roots in the early 19th century.

Sluices designed by Thomas Telford were built at the lake not so much to protect Bala but to ensure his newly constructed Llangollen Canal had a constant and sufficient supply of water via the River Dee. His engineering meant water levels were raised in Llyn Tegid, enlarging what was already the largest natural body of water in Wales. Join the North Wales Live Whatsapp community now

More than a 150 years later, this form of river regulation was substantially refined. A scheme originally conceived before World War 11 was put into practice in the 1950s, aiming both to sustain the River Dee during low flows while reducing flooding in the Dee valley. In turn, this would increase the amount of drinking water available for abstraction.

New sluice gates were built near Bala and Dee inflows were controlled by water from Llyn Brenig and, via Afon Tryweryn, from Llyn Celyn. Now, Llyn Tegid acts as a balancing reservoir for the Dee system.

In summer, levels are kept artificially high. In autumn, water is discharged ready for an influx of winter rain. As a water storage facility that also drives hydro plants, the Dee system acts as a giant battery.

It means that, each year, the lake’s water levels can vary by as much as 40cm (about 18 inches). Calculating when to release water from Llyn Tegid and its reservoirs is a task for the computers at Bala's control centre.

This way, the lake fluctuates differently from most others, which typically shrink in dry weather. So the recent Bala visitor need not be alarmed: Llyn Tegid has yet to replenish - it's waiting to do its job of reducing the risk of winter flooding to communities in the lower Dee Valley.

Neither has the recent dry spell detracted from its appeal to others. “It hasn’t rained substantially for weeks,” said a Bala man. “And it is still one of the most beautiful locations on planet earth.” Get all the latest Gwynedd news by signing up to our newsletter - sent every Tuesday

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