The source of the UK’s longest river

This is what crossing Pumlumon does to you (to the writer, anyway!) © Chris Hassan

Walk length: 16km (out and back).

For an upland that can make so many bold claims (highest point in Mid Wales, one of the greatest uninterrupted wildernesses in Wales and, as will shortly be elaborated upon, the source of Britain’s longest river, fifth-longest river and the longest two to flow across Welsh soil), Pumlumon is a very unfrequented place. We can vouch for that. When we went there this August, on the search for the source of the River Severn, the longest river in the UK, we scarcely saw another soul.

A few walkers do ascend to the loftiest point of land hereabouts, Pen Pumlumon Fawr, snap some shots of the summit cairn and the giant reservoir of Nant-y-Moch splayed dramatically below, then return whence they came. Unless you are in the trickle of hikers walking the Cambrian Way, or the even thinner trickle of walkers motivated to traipse this massif’s other wild pathways, you don’t make any further incursions into Pumlumon. You just don’t. Which is part of the reason why we did, late this summer just gone.

The day we went, there was only one other walker on the Pen Pumlumon Fawr summit and then, as one half of Undiscovered Wales and an equally wilderness-obsessed friend forged onwards, eastwards and then northwards over the yellow-green hills, absolutely nobody for the next four kilometres. Nobody as we bent this way and that through some of Wales’ very finest moorland scenery on our way to where Britain’s longest river began…

The route: to the Severn’s source

The best route to get up onto the upland is not the way we came (so we will not regale you with another one of those ‘lost in the bog’ stories!) The best way begins where we have in the past, at the car park in the little hamlet of Eisteddfa Gurig, and climbs to Pen Pumlumon Fawr via a fairly straightforward trail. Do not be tempted to walk from Ponterwyd just because the nearest pub is there – the only trail up becomes impossible to follow, obscured by bog and plantations.

From the summit cairn, the path follows a distinct field boundary east (yes, you need a compass for this walk ideally!). Just down off the highest ground as you descend a dip between Pen Pumlumon Fawr and the next, unnamed rise, there are spectacular views north over Llyn Llygad Rheidol, with the peaks of southern Snowdonia peppering the skyline.

From the top of the unnamed rise (about 1km from Pen Pumlumon Fawr), you behold, looking about you, an awful lot of yellow-brown undulations of moorland and, perhaps because the view is so moor-dominated, landmarks that might otherwise have remained insignificant assume new importance. A good example of this are the number of boundary marker stones, some on natural rocks but most on stone posts, emblazoned with the letters ‘WWW’ – not the World Wide Web making an encroachment on this untouched-by-modern-times terrain but a reference to one of the biggest landowners in this part of Wales in Victorian era, Watkins William-Wynn. 

It’s just beyond here, as our route switches direction slightly more west-northwest, with a steepish drop down to lower moorland now immediately on the right, that the day’s first river source comes into view. Without any fanfare whatsoever, an area of morass with a couple of thin stream gullies issuing from it further down indicates the beginning of the River Wye (Britain’s fifth-longest waterway and the river responsible for the birth of modern British tourism, incidentally, but that we suppose is another story). The Wye Valley Walk begins here and leads down, through Llangurig and Rhayader to Newbridge-on-Wye, Hay-on-Wye, Symonds Yat, Monmouth and Tintern to Chepstow.

On we go. The path now ascends another 1km another named summit, Pen Pumlumon Arwystli, with the route passing just right of, and below, the summit along a fenceline with an area of rather deforested forest falling away to the right. The path descends 350m to meet another fence at the corner of this former forest, with this boundary descending noticeably to the right (east). However the route to the source of Britain’s longest river skips to the left (without crossing the fence) to a stone visible 200m away and on slightly higher ground to the left. A distinct (although hardly well-trodden) route now bears slightly down, tracing a rather decrepit fence on the right and in an almost due north direction, crossing a couple of cross-fences on stiles in need of maintenance to reach two tiny tarns after a further 1km.   

Just beyond here, it comes as quite a shock, after such a barren stretch of moor, to encounter a very well-maintained stile set in the fence on the right. Even more surprisingly, a path studded with actual proper paving stones ( a welcome break from the bogginess underfoot) weaves from here between an area of bog so raised the reeds are at points almost head height to the biggest indication of civilisation anywhere on the top of this massif: the source. This is indicated by a broad area of neatly-positioned stone slabs, centred by a hefty pointed wooden post as high as the bowed head of a rather weary hiker with the words ‘TARDDIAD AFON HAFREN – SOURCE OF THE RIVER SEVERN’ etched down its sides. Alongside the paved area are the boggy puddles which are the first tangible sign of the water source, which no doubt actually begins somewhere in the sopping morass nearby. 

Having with us a life straw, a water filter that enables you to slurp from 99% of the world’s waters supposedly without any ill effects, we decided there was no better test of it than to take a well-earned drink from the rather black-looking pools. And so we are able to ‘take the waters’ at the source of the most major river either of us had ever been up close and personal to. And be privy to a startlingly stark and scenic area of Mid Wales moor at the same time.

The River Severn, too, has a trail to accompany it, and the Severn Way coils its way down from here, all 224 miles of it, to Bristol. There is another road access to the source of the River Severn if you follow this trail 4.5 miles down into the valley via the beautiful Blaenhafren Falls you come to Hafren Forest Car Park, itself accessible by road from the western end of Clywedog Reservoir.

Standing there by the source of the River Severn, we think of the Romantic poets and how they loved utilising that metaphor of the spring (as in the water source, not what supports your mattress): from a humble origin underground surges forth an often-mighty river that thrills along its upper course with its waterfalls, irrigates countless fields and provides a setting for towns and cities lower down and finally, with much aplomb, to onlookers lounging on its beaches or fishing in its estuaries, enters the sea.

And all this starts with a bog. 

Then we turn around, and walk back.   

NEXT ON THE JOURNEY: From the source of the River Severn, it’s 29 miles west to the impressive sand dunes of Ynyslas.

At a glance

How to get there: Access from Eisteddfa Gurig, on the A44 between Aberystwyth and Llangurig (as detailed in our article on climbing Pen Pumlumon Fawr). Follow our description in that post of how to get to Pen Pumlumon Fawr, the first part of the walk described here.

Parking: At Eisteddfa Gurig, as described in our article on climbing Pen Pumlumon Fawr)

Refreshments: Bring food with you. Technically the nearest food and drink would be at the George Borrow Hotel in Ponterwyd, further down the A44 past Eisteddfa Gurig towards Aberystwyth.

Best time to visit: The weather is a fickle beast, out here, but we recommend a clear day so you get some sort of view from Pen Pumlumon Fawr on the way. Just remember all of this upland is very exposed and the winds blowing across from Snowdonia can be biting: bring warm clothes at any time of year, even if you’re in a t-shirt at the bottom of the climb!

Map: