is a

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

Gwynedd Gwynedd () is a county in the north-west of Wales. It borders Anglesey across the Menai Strait to the north, Conwy, Denbighshire, and Powys to the east, Ceredigion over the Dyfi estuary to the south, and the Irish Sea to the west. The ci ...

, Wales, which has its source in a wide area north of Dduallt in

Snowdonia Snowdonia, or Eryri (), is a mountainous region and National parks of the United Kingdom, national park in North Wales. It contains all 15 mountains in Wales Welsh 3000s, over 3000 feet high, including the country's highest, Snowdon (), which i ...

. It is 28 miles (45 km) in length, and is much branched; many of the significant tributaries are of a similar size to the main river. The catchment area is bounded to the east by the

Aran Fawddwy Aran Fawddwy is a mountain in southern Snowdonia, Wales, United Kingdom. It is the highest point (List of counties of England and Wales in 1964 by highest point, county top) of the historic county of Merionethshire (for local government ...

massif and to the west and north by the

Harlech Harlech () is a seaside resort and community (Wales), community in Gwynedd, North Wales, and formerly in the Historic counties of Wales, historic county of Merionethshire. It lies on Tremadog Bay in the Snowdonia National Park. Before 1966, it ...

dome which forms a watershed just south of

Llyn Trawsfynydd Llyn Trawsfynydd is a large artificial reservoir situated near the village of Trawsfynydd in Gwynedd, North Wales. With a total surface area of the reservoir is slightly more extensive than Wales's largest natural lake, Bala Lake at . History ...

. The Mawddach has been the site of significant industrialisation and land management. Gold mining and subsequently

gold panning Gold panning, or simply ''panning'', is a form of placer mining and traditional mining that extracts gold from a placer deposit using a pan. The process is one of the simplest ways to extract gold, and is popular with geology enthusiasts espec ...

have had major impacts but forestry, the preparation of animal skins, the storage of old munitions and the use of hill-sides as artillery ranges have all added to the legacy of pollution. The river is also very ''flashy'' - prone to very rapid rise and fall in level depending on rainfall. Rainfall can also be very heavy and it falls on very base-poor soils leading to episodes of strongly depressed pH. Despite this, the river sustains an important

salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...

and

trout Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...

fishery and the countryside through which it flows is some of the most spectacular and scenic in the UK. The main tributaries starting in the west and working clockwise are: * Afon Cwm Mynach which drains Llyn Cwm Mynach on the Rhinogydd. *

Afon Gamlan This is a list of rivers of Wales, organised geographically. It is taken anti-clockwise from the Dee Estuary to the M48 Bridge that separates the estuary of the River Wye from the River Severn. Tributaries are listed down the page in an upstre ...

which joins at

Ganllwyd Ganllwyd is a small village and Community (Wales), community in southern Gwynedd, Wales. It lies in the Snowdonia National Park to the north of Dolgellau. A470 road, A470 passes through it. The Community population taken at the United Kingdom ...

after following a tumultuous valley through ancient

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

woods before descending towards the main river down Rhaeadr Ddu (''Black waterfalls''). This valley has one of the more important

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

and

liverwort Liverworts are a group of non-vascular land plants forming the division Marchantiophyta (). They may also be referred to as hepatics. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry ...

communities in the southern UK. * Afon Eden - its headwaters known as Afon Crawcwellt - a large tributary draining from below

and closely following the

A470 The A470 (also named the Cardiff to Glan Conwy Trunk Road) is a trunk road in Wales. It is the country's longest road at and links the capital Cardiff on the south coast to Llandudno on the north coast. While previously one had to navigate th ...

through the Coed-y-Brenin forest. This tributary has been severely affected by

industrialisation Industrialisation ( UK) or industrialization ( US) is the period of social and economic change that transforms a human group from an agrarian society into an industrial society. This involves an extensive reorganisation of an economy for th ...

in the past, including

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

mining and its use as an ordnance range. * Afon Gain, a large tributary which has also been impacted by similar problems to the Eden and is very acidic and peaty. * Afon Wen which joins south of the Gain is similar but smaller. *

Afon Wnion The River Wnion is a river in the southeast of Gwynedd, Wales. It begins high on the slopes of Aran Benllyn about five miles south of Lanuwchllyn and flows south-west into the River Mawddach near Cymer Abbey. It flows past several villages, ...

is a major tributary joining from the east and which drains a large area out towards

Estuary

Below

Dolgellau Dolgellau (; ) is a town and Community (Wales), community in Gwynedd, north-west Wales, lying on the River Wnion, a tributary of the River Mawddach. It was the traditional county town of the Historic counties of Wales, historic county of Merion ...

the river enters a wide and sandy estuary. The head of the estuary is marked by the confluence of the Mawddach and Wnion. At its mouth is the town of

Barmouth Barmouth (formal ; colloquially ) is a seaside town and community in the county of Gwynedd, north-west Wales; it lies on the estuary of the Afon Mawddach and Cardigan Bay. Located in the historic county of Merionethshire, the Welsh form of t ...

and its

railway bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somet ...

Geology

The Mawddach estuary was formed from a glaciated valley which was flooded by the sea during the

Holocene glacial retreat The Holocene glacial retreat is a geographical phenomenon that involved the global retreat of glaciers ( deglaciation) that previously had advanced during the Last Glacial Maximum. Ice sheet retreat initiated ca. 19,000 years ago and accelerated af ...

to form a

fjord In physical geography, a fjord (also spelled fiord in New Zealand English; ) is a long, narrow sea inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Antarctica, the Arctic, and surrounding landmasses of the n ...

. The valley occupied by the present Mawddach was later infilled by coarse-grained sub-glacial and pro-glacial deposits. In the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

(12,000 BP - present), gravel from the Irish Sea was introduced to the estuary.The late devensian and holocene evolution of Barmouth Bay, Wales, Piers Larcombe, 1994

Human history

The southern bank of the Mawddach estuary, along which used to run a section of the GWR branch line from

Ruabon Ruabon (; ) is a village and community in Wrexham County Borough Wrexham County Borough () is a Principal areas of Wales, county borough, with city status in the United Kingdom, city status, in the North East Wales, north-east of Wales. I ...

, has now been designated the Mawddach Trail, an 8-mile cycle path running from Dolgellau to Morfa Mawddach, at the south side of the Barmouth railway bridge. It is managed by the Eryri National Park Authority as a leisure route for walkers and cyclists, and is part of the

Sustrans Sustrans ( ) is a United Kingdom-based walking, wheeling and cycling charity, and the custodian of the National Cycle Network. Its flagship project is the National Cycle Network, which has created of signed cycle routes throughout the United ...

Cross-Wales Cycling Route. The estuary of the Mawddach was a great centre of

ship building Shipbuilding is the construction of ships and other floating vessels. In modern times, it normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces i ...

in the 18th century and probably for some centuries before. There is no evidence remaining of this activity in the estuary today.

References

External links

River Mawddach panorama

Aerial photograph of Cadair Idris and the river Mawddach

The Mawddach Trail - The 'Railway Walk' between Dolgellau and Barmouth

The Mawddach Way: A 50km Circular Walk around the Mawddach Estuary

Mawddachestuary.co.uk - Events and Activities along the Mawddach Estuary

{{authority control Mawddach Mawddach