Lough Derg, Ireland

Lake Locations:

Ireland - Shannon Region -

One of Ireland’s most pristine national treasures is Lough Derg, a 29,000-acre lake nestled within western Ireland’s Shannon Region. Its title comes from the word “Loc Dergdherc”, meaning the “lake of the red eye.” The name was derived from an old Irish legend about a king, a lake monster and a hero. It is the last and largest of three lakes along the River Shannon; the other two lakes are Lough Ree and Lough Allen, both to the north.

Lough Derg is a freshwater lake situated within three counties: County Clare to the south, North Tipperary to the east and Galway to the north and west. It should not be confused with a lake by the same name in County Donegal.

The lowest body of water on the Shannon lake system, Lough Derg features an average depth of 25 feet, a maximum depth of 118 feet, and a shoreline length of 111 miles. Water levels are regulated by the ESB (Electricity Supply Board) via sluices at Parteen Weir. Measuring in at 23 miles long, it is the third largest lake in Republic of Ireland.

By observing the irregular texture of Lough Derg’s floor, scientists speculate that the lake is the result of ancient ice erosion. In the 1800s, locals took advantage of its more than 23 miles of navigable length and turned it into a hotspot for trading and commerce. An electric power plant at Ardnacrusha was implemented at Lough Derg in 1927.

Today, Lough Derg is known as “Ireland’s Pleasure Lake” because of its vast recreational opportunities. Sailing, swimming, boating and angling are its main pastimes, along with windsurfing, and yachting. Various luxury and pleasure cruises offer journeys in utmost comfort and style.

Perhaps the most phenomenal activity on Lough Derg is canoeing or kayaking out to its Holy Island, a monastic settlement dating back to the 7th century. Here you can browse the remnants of five churches, monastic cells, and a cemetery dating from antiquity to the 1100s. Just over a mile from Mountshannon, its ancient name is “Inis Cealtra,” or “Island of the Graveyard.” Let your imagination run wild as you explore its 80-foot round tower, collection of bullaun stones and sacred well on this 50-acre island. (Bullaun stones refer to depressions in stones that fill with rainwater, pebbles or other stones; they are believed to have magical or curative powers.)

Fishing is another popular pastime at Lough Derg, where brown trout average between one and two pounds; pike and course fish also inhabit the lake. While the season opens in March, Mayfly season is the best time to come – when trout spawn on the Little Brosna/Camcor Rivers. Fishing companies offer excursions including boat, gillies, bait and tackle, plus hotel, transportation and meals.

Active types will love hiking the waterway paths around Lough Derg. Portumna Forest Park and Lough Derg Way Hillwalks each take about 2.5 hours. The Dromaan to Williamstown Walk is perfect for a full day hike, covering an incredible 13 miles of stunning terrain. East Clare Way Limited also offers five circular trails that are popular with outdoor lovers.

Equine enthusiasts can’t get enough of horseback riding Lough Derg’s forest trails, mountain paths and coastlines. The Galway Clare Burren Trail takes six days to complete from start to finish, with a terminus at the legendary Cliffs of Moher, a Refuge for Fauna and Special Protection Area for Birds since the late 1980s.

Driving around the Lough Derg is one of the simplest ways to enjoy Ireland’s lush countryside. Routes are perfect for exploring old watermills, taking in breathtaking views, and eating at some of the finest restaurants in Ireland. Following the road northward along the River Shannon, you’ll pass a mound called Brian Boru’s fort. After this, plop down for the perfect picnic at a nearby bay, where you can watch windsurfers and kayakers in action. Next pass through the town of Ogonelloe and on to Scarriff Bay’s beautiful observation area. Continuing on through various towns – like Tumangraney, Mountshannon, and Portumna – you’ll finally arrive at the ancient community of Nenagh.

Ample facilities are available all around Lough Derg, including several marinas with picnic areas, tennis courts, children’s play areas, pubs, restaurants and shops. The University of Limerick owns an impressive activity center along the shore at Killaloe. Additionally the Lough Derg Science Group, a coalition of independent scientists established in 2003, has several aquatic research studies underway.

Numerous real estate properties, apartment rentals and Irish holiday cottages are dotted throughout the Lough Derg area; expect to find them tastefully decorated and with elegant decor. Many feature en-suite style rooms and beautiful lakeside vistas. Whether you come for an unforgettable family vacation, a romantic honeymoon, or a solo-getaway you’re sure to find enormous peace and tranquility at Lough Derg.

Things to do at Lough Derg

  • Vacation Rentals
  • Fishing
  • Boating
  • Sailing
  • Swimming
  • Canoeing
  • Kayaking
  • Tennis
  • Picnicking
  • Hiking
  • Horseback Riding
  • Birding

Fish species found at Lough Derg

  • Brown Trout
  • Pike
  • Trout

Lough Derg Photo Gallery

Lough Derg Statistics & Helpful Links

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Lake Type: Natural Freshwater Lake, Dammed

Water Level Control: Electricity Supply Board (ESB)

Surface Area: 29,158 acres

Shoreline Length: 111 miles

Normal Elevation (Full Pond): 111 feet

Average Depth: 25 feet

Maximum Depth: 118 feet

Water Volume: 719,103 acre-feet

Water Residence Time: 2.4 months

Drainage Area: 3,969 sq. miles

Trophic State: Eutrophic

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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".

You can find many of the world's highest-elevated lakes on LakeLubbers. Lakes with the lowest elevations (known by LakeLubbers) are shown on the final page of that list.


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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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