Afon Aeron

November 2024

Very few rivers have escaped physical modification by humans at some point in their history. In Britain, less than 1% are free of artificial barriers. Many have also had sections straightened, culverted or their banks re-enforced with artificial material, usually for road building, flood defence and agriculture.

The Afon Aeron in West Wales is no different. Rising from Llyn Eiddwen in the Mynydd Bach hills of Ceredigion, this relatively small river (around 23 miles in length) is almost semi-circular in shape. From its source it first flows south west, then arcs north west before reaching Cardigan Bay at the harbour town of Aberaeron. No more than a handful of houses in 1800, Aberaeron expanded rapidly into a bustling port in the early nineteenth century but nowadays is better known for its colourful quayside properties and restaurants.

Llyn Eiddwen, the source of the Aeron on the Mynydd Bach hills. Photo: Paul White/People’s Collection Wales

Salmon and sewin trying to ascend the Aeron to their spawning grounds are almost immediately faced with a series of weirs. These obstacles also have to be negotiated by juvenile fish making their way downstream.

One of the Aeron’s tributaries. What should be a productive sewin spawning stream is now a featureless agricultural drainage ditch.

World War I German prisoners of war at Fron-goch camp in North Wales. Gangs of POWs were used to fill gaps in the agricultural labour force as the war took its toll. In the Aeron catchment, they were used to improve drainage of agricultural land.

The Afon Aeron at Llangeitho
(cc-by-sa/2.0 – © Roger D Kidd – geograph.org.uk/p/2536856)

Aeron barriers

For Atlantic salmon and sewin returning to the Aeron from the sea to spawn, the impact of humans is immediate. A series of five weirs confront them in Aberaeron. All are passable for the fish in the right flows but in combination, they present an impediment to passage to their spawning grounds in the headwaters, leaving them more vulnerable to predation. Perhaps more damagingly, juvenile salmonids on their way to sea pause at such structures. Human consumption of these small outbound fish may have ceased but a host of other predatory mouths still await.

The Aberaeron weirs were probably built so that the once abundant stocks of salmon and sewin could be caught more easily. An article in the Cambrian News in 1916 reported an attempt to remove one of them with explosives. The weir had been built six years before that by the local Fishery Board and anglers were divided in their opinions over it.

One group, who were known locally as “Moonlighters”, thought that the deeper weir pool would give the fish a resting place having entered the river. Others (described in the paper as “Sin Feiners”) thought that it gave poachers too good an opportunity. After years of heated arguments, it seems the Sin Feiners took matters into their own hands.

However, human modifications to the Aeron had begun well before then. The river had been diverted through Aberaeron’s new harbour in 1807. Other weirs had also been installed further upstream to power a number of wool mills. Here the millers were suspected of setting traps in the leats for juvenile salmonids on their way to sea. Fortunately, many of these upstream weirs are not longer standing.

Agriculture’s influence

Agriculture too has made physical changes to the natural flows of the Aeron. The straightening of rivers and streams for land drainage purposes has been common practice for centuries, with the objective of increasing productivity in areas that would otherwise be too wet to be of any use. Large areas of upland Wales that would otherwise be uninhabitable, impassable and unfarmable have been transformed this way.

But it comes at a cost. Straightened, unnatural rivers quicken flows and reduce the ability of catchments to store water. They exacerbate flooding downstream impacting communities such as Aberaeron where previous flood events have damaged properties. In dry periods less water is released to sustain flows. The faster a river is, the more sediment, nutrients and other chemicals are stripped from the land. Modified rivers do not have the habitat diversity of naturally meandering rivers and as a consequence, are much less biodiverse. They are bad news for fish and other aquatic wildlife.

The fertile Aeron valley has a rich agricultural heritage. Although the river’s name is associated with warfare, it is also the Welsh word for “berries.” The valley’s agricultural wealth enabled ten estate houses to be built between Tal-sarn and Aberaeron by the start of the twentieth century.

Straightening local streams was all part of the plan to extract as much as possible from the land. In 1918 and with an obvious shortage of labour, German prisoners of war were being used to dig out Aeron tributaries to improve the land drainage.

Earlier, in 1874 a farmer wrote in to the Aberystwth Observer to say:

“The rubbish carried by the rivulet WaIIen (Nant Rhiwafallen) to the river Aeron blocks the course of the latter more than two-thirds up the valley. Occasional washing makes the meadows more sprightly and fresh but stagnant pools, marshy flats, and dead water carriers are a great loss and a nuisance to the farmer, as well as being anything but advantageous to the successful rearing of cattle. No one who watches the effect of draining on the Ystrad flats, and the want of it on the Talsarn flats, will doubt for a moment the great advantage which is derived from good drainage.”

A West Wales Rivers Trust survey of the Aeron catchment found evidence of these modifications to the river’s main stem. Some tributaries had also been turned into no more than straight, featureless agricultural ditches. No longer were they the kind of natural stream in which the Aeron’s sewin could spawn in and juveniles thrive.

Encouragingly, the reprofiling of artificially straightened rivers (sometimes called “re-wiggling”) to “reconnect” them with their floodplains is gathering apace in river restoration work across the UK. More than 2,500km has been restored since the early 1990s but while this sounds impressive, it amounts to less than 3% of the damaged river network.

Much more is needed. One of the many restoration recommendations the West Wales Rivers Trust has made is to work with landowners to re-profile the Aeron and its tributaries to make a more natural catchment. This type of work has proven benefits not just for rivers but for soil health too. Raising the project funds will be a challenge, as will gaining trust locally to make the landscape changes required.