Llyn Brianne Reservoir, Wales, United Kingdom

Lake Locations:

United Kingdom - Wales - Mid Wales -

Also known as:  Llyn Brianne, Lake Brianne

The Llyn Brianne Reservoir is a beautiful 530-acre (2.1 square kilometer) body of water nestled in the Cambrian Mountains of Mid-Wales. Created in 1972 by damming a section of the River Towy, the reservoir’s purpose is to store winter rain and snowmelt that can be released into the river during dry periods. The River Towy supplies a large part of south Wales with drinking water and would be in danger of going dry if it were not for the release of water from the upland reservoir. In addition to a constant flow of water, Llyn Brianne offers a haven for fishermen, bird watchers, mountain bikers and walkers.

Set in an area known as Little Switzerland, Llyn Brianne or Lake Brianne is just north of Llandovery and extends for three miles towards Tregaron. The Upper Towy Valley is considered one of the most beautiful areas of Wales. The rolling Cambrian Mountains fill the space between their better-known neighbors, Snowdonia to the north and Brecon Beacons National Park to the south. A peaceful, largely unspoiled area with a rich cultural history and vibrant natural beauty, Llyn Brianne attracts a wide range of outdoor enthusiasts and nature lovers.

The most notable tourist attraction of Llyn Brianne is the massive spillway of the dam when the reservoir releases water. The dam is the United Kingdom’s tallest, standing at a height of 300 feet (91 meters), and is the world’s largest clay core dam. In 1996 the reservoir spillway was increased by three feet (one meter) in height and a hydro electric generating station was added to the base of the dam. When all three turbines are operating, the station can generate 4.3 megawatts of electricity. The spillway was recently made famous by kayakers who filmed themselves racing down the spillway at over 40 mph (64 kph). Welsh Water, owners of the dam, issued a statement in 2008 calling the practice “dangerous” and stating that such activities were banned at the reservoir. The Llyn Brianne dam can be found at the conjunction of the counties of Ceredigion, Carmarthenshire and Powys, north of Llandovery.

Llyn Brianne’s close proximity to Llanwrtyd Wells makes it popular with extreme sport enthusiasts. The town of Llanwrtyd Wells is known for its mountain bike trails which loop through thousands of acres of forest and hillside. Hiking the trails is also a popular pastime with nature enthusiasts and bird watchers.

With a maximum depth of 278 feet (85 meters), Llyn Brianne Reservoir is a favorite with boaters and anglers. Because Llyn Brianne is a fresh water reservoir, motor boats are not allowed. Sea trout and salmon can be found in the reservoir, but the River Towy has an excellent reputation for its gigantic sea trout. The River Towy (or Afon Tywi in Welsh) is the longest river which runs entirely through Wales. On its 68-mile (109-kilometer) long journey seaward, the river runs south-westwards through Carmarthenshire where it flows through the towns of Llandovery and Llandeilo. It is joined in Camarthen by the tributary Afon Gwili at Abergwili which adds a substantial amount of water to the river’s flow. The Towy then flows into Carmarthen Bay, where it shares a combined estuary with the River Taf and River Gwendraeth. A 12th Century Norman castle, Llansteffan Castle, stands guard over the mouth of the Towy estuary.

Visitors to the Llyn Brianne area will have no trouble finding accommodations. For vacation rentals and holiday cottages, the beautiful village of Rhandirmwyn offers hotels, bed & breakfasts, and a number of self-catering options. Additional accommodations can be found in the towns of Llandovery and Llanwrtyd Wells. Brecon Beacons National Park is an easy drive south of Llyn Brianne and offers camping and caravan parks as well as some of the highest mountain peaks in South Wales.

Although a rather isolated area, the landscape around Llyn Brianne has much to offer tourists and year-round residents. Downstream from Llyn Brianne, the Dinas Bird Reserve is home to a rare pair of breeding Red Kites as well as other endangered birds. The Dinas Reserve offers walks along the cascading River Towy and through the stunning forestland in the area. The National Botanic Garden of Wales is located in Carmarthenshire and features beautiful flora and fauna, much of which is displayed under a gigantic glass dome which has the largest single-span glass roof in the world. A few miles west of Llandovery, near the village of Pumsaint, the Dolaucothi Gold Mines are great for a family adventure. Guided tours take visitors into the mines and a museum, gift shop and cafe offer a place to rest and relax.

In addition to Llansteffan Castle, the ruins of Carreg Cennen Castle can be found southeast of the town of Llandeilo which is southwest of Llyn Brianne. Constructed in the 1300s, the impressive fortress sits at the top of a cliff. Trails lead up to the castle and there are also cafes, gift shops and picnic areas along the way. Be sure to bring your camera because the castle and the view are quite amazing.

Set in a quiet location conveniently close to mountain biking and hiking trails, bird watching, horseback riding, and fishing, Llyn Brianne Reservoir has much to offer the outdoor enthusiast. Featuring some of the region’s most scenic and secluded countryside, the wild beauty surrounding Llyn Brianne and the Upper Towy Valley makes it one of Wales’ most exhilarating places to visit.

Things to do at Llyn Brianne Reservoir

  • Vacation Rentals
  • Fishing
  • Boating
  • Kayaking
  • Camping
  • Picnicking
  • Hiking
  • Biking
  • Horseback Riding
  • Birding
  • National Park
  • Museum
  • Ruins

Fish species found at Llyn Brianne Reservoir

  • Salmon
  • Trout

Llyn Brianne Reservoir Photo Gallery

Llyn Brianne Reservoir Statistics & Helpful Links

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Lake Type: Artificial Reservoir, Dammed

Water Level Control: Dwr Cymru Welsh Water

Surface Area: 530 acres

Normal Elevation (Full Pond): 908 feet

Maximum Depth: 278 feet

Water Volume: 48,643 acre-feet

Completion Year: 1972

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Trophic State | LakeLubbers

Trophic State measures the level of algae and nutrients in a lake.

An oligotrophic lake is very clear (blue in color) and does not support much plant or fish life. A hyper-oligotrophic lake is the clearest of all lakes, and is nearly devoid of plants and fish.

A mesotrophic lake is slightly green and supports a moderate degree of plant and fish life. A lake's most desired trophic state is generally this mid-point - the mesotrophic state.

A eutrophic lake is somewhat murky and supports a large amount of plant and fish life. A hypereutrophic lake is clouded with algae, plant life, and fish life. A eutrophic or hyper-eutrophic lake can be difficult to navigate by boat - and is often an unpleasant place to swim.

The use of phosphorus-rich and nitrogen-rich fertilizer on lawns and golf courses surrounding a lake can cause it to become eutrophic or hypereutrophic.


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Catchment or Drainage Area | LakeLubbers

This is the surrounding area that drains into a lake, including land, rivers and their tributaries. This is also known as the lake's "catchment basin".

Small lakes at the highest peaks of mountains have small drainage areas. The world's oceans have the largest drainage areas.


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Lake-Area Population | LakeLubbers

This is the estimated number of people who live in a house with a view of a lake, plus those who self-describe the lake as their home, for example: "I live at Smith Mountain Lake."


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Water Residence Time | LakeLubbers

This is the estimated time that it takes for an amount of water equal to the entire volume of a lake to flow out of - or evaporate from - the lake.

Residence Time can be as short as a few days for fast-flowing small lakes, and can exceed 100 years for slow-flowing large lakes.


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Completion Year | LakeLubbers

This is the year that a reservoir was first filled to the reservoir's normal elevation - or the year that a natural lake was first dammed. A large reservoir can take more than a year to fill after its dam is first closed.

The Grand Anicut in southern India is generally considered the world's oldest dam that still operates. Grand Anicut was constructed in the second century BC. It now impounds an irrigation network that includes roughly one million acres.

You can find many of the the world's newest reservoirs on LakeLubbers. Many of the world's oldest reservoirs appear on the last page of that list.


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Water Volume | LakeLubbers

This is the estimated volume of water that a lake contains -- measured at the lake's normal elevation. By this measure, the world's largest freshwater lake is Siberia's Lake Baikal.

You can find many of the the world's largest lakes (by water volume) on LakeLubbers.

Water Volume can be measured in acre-feet, in cubic miles, or in cubic kilometers. One acre-foot is the amount of water needed to cover one acre (43,560 square feet) to a depth of one foot. One cubic mile equals 3,379,200 acre-feet. One cubic kilometer equals 810,713 acre-feet.

1 acre-foot is equal to 325,851 US gallons. Siberia's Lake Baikal contains about 6,276,367,740,000,000 gallons of freshwater - nearly 1 million gallons for every living person on earth.

The other - and more widely used - measure of a lake's size is the lake's surface acreage. By that measure, the world's largest freshwater lake is North America's Lake Superior.


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Maximum Depth | LakeLubbers

This is the estimated greatest depth of the water in a lake -- measured at the lake's normal elevation. The world's deepest lake is Siberia's Lake Baikal; that lake's maximum depth is estimated at 5,314 feet.

You can find many of the the world's deepest lakes on LakeLubbers. If you select the last page of that list, you will find the (maximum depth of) the shallowest lakes in our database.


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Average Depth | LakeLubbers

This is the estimated average depth of the water in a lake -- measured at the lake's normal elevation. If the water volume and surface area of a lake are known, an estimate of the lake's average depth can be calculated:

Water volume ÷ Surface Area = Average Depth

Example: 1,000,000 acre-feet ÷ 20,000 acres = 50 feet average depth


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Maximum Elevation | LakeLubbers

This is a lake's highest water level, measured by the lake's surface distance above sea level, that can occur during flooding. A lake's highest possible maximum elevation is usually the top of the lake's dam or spillway.

At lakes that include residential development, government regulations usually forbid the construction of homes below a lake's maximum elevation.


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Minimum Elevation | LakeLubbers

This is a lake's lowest water level, measured by the lake's surface distance above sea level, that can be reasonably expected to occur. Low lake levels can occur due to deliberate seasonal draw downs for irrigation or impending snow melt, reduced water inflows, drought and evaporation, residential or commercial water demands, and hydropower generation.

Some lakes' minimum and maximum elevations are virtually the same. Lakes that generate hydropower may vary by several feet - according to power demand. Lakes whose primary purpose is to prevent flooding can seasonally vary by 100 feet or more.

When some lakes reach their minimum elevation, their boat ramps may not be long enough to permit boat access - and boats docked on shallow parts of the lake may end up on dry ground. In those cases, kayakers and shore-based anglers may be among the few happy recreational users of the lake.


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Normal Elevation | LakeLubbers

This is a lake's normal water level, measured by the lake's surface distance above sea level. For a reservoir, this water level is also known as "full pond" or "full pool".

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Shoreline Length | LakeLubbers

This is the length of the exterior shoreline around a lake - measured at the lake's normal elevation. The shoreline length can be considerably shorter or longer when lake water levels are lower or higher than normal.

A lake with many coves has a much longer shoreline than a lake of similar surface area that is nearly circular in shape.

When known, the shoreline miles that we report in our statistics include only the lake's exterior shoreline, and exclude the shorelines of islands located within a lake's boundaries. In lakes with many islands, those islands' combined shorelines may exceed a lake's exterior shoreline.

You can find many of the world's longest-shoreline lakes on Lakelubbers.


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Surface Area | LakeLubbers

This is the area (acreage, square kilometers, etc.) of the top surface area of a lake - measured at a lake's normal elevation. The surface area can be considerably smaller or larger when lake levels are lower or higher than normal. North America's Lake Superior is the world's largest freshwater lake by this measure.

The other measure of a lake's size is the lake's water volume. By that measure, the world's largest freshwater lake is Lake Baikal in Siberia.

You can find many of the world's largest lakes (acres) on Lakelubbers. There is no widely-accepted minimum surface area that defines a lake. What Lakelubbers describes as a lake, you might call a pond. The smallest lake that Lakelubbers currently includes is Hawaii's 2-acre Lake Waiau.


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Water Level Control | LakeLubbers

This is the organization that controls water releases or outflows from the lake or reservoir. In the USA, this is often the US Army Corps of Engineers, a power company, a municipal water system, an irrigation district, or a paper manufacturing company. In the case of private or gated lakes, a homeowners' association may be the lake's controlling authority.

Many lakes cross borders, including North America's Great Lakes. The control of such lakes and their coveted freshwater may be amicably shared - or hotly disputed.

"Water wars" continue at many lakes as growing populations and crop irrigation needs compete for the freshwater that lakes contain.


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Lake Type | LakeLubbers

There are 3 basic types of lakes that are currently included on LakeLubbers. 2 types may be dammed or not dammed, producing 5 classifications.

- A Reservoir is a man-made freshwater lake that is usually created by damming rivers.

- A Natural Freshwater Lake occurs naturally - often by glacial activity - and has a salinity of less than 30 parts per thousand. It may be dammed to produce electricity or for other reasons.

- A Natural Saltwater Lake occurs naturally and has a salinity of more than 30 parts per thousand (ppt). It may be dammed.

"Brackish" water may be categorized as freshwater or saltwater, depending on its salt content (salinity). Oligohaline water has less than 15 ppt of salt. Mesohaline water has 15-29 ppt. Polyhaline has 30-335 ppt.


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