Lake Arenal, Alajuela & Guanacaste, Costa Rica

Lake Locations:

Costa Rica - Alajuela - Guanacaste -

Also known as:  Lago Arenal, Laguna de Arenal

Lake Arenal, flanked by lush rainforest and the magnificent Arenal Volcano, is a world-class destination lake. Known for its feisty rainbow bass and incredible winds, the lake is a favorite among anglers, windsurfers and sailboarders. Nearby La Fortuna, known as the adventure capital of Costa Rica, adds to the mix cave spelunking, bungee jumping, whitewater rafting, canopy (zip-line) tours, and waterfall rappelling. Yet Lake Arenal’s daring spirit is tempered by groomed hiking trails, wildlife watching (monkeys included), and spectacular scenery, making it an ideal lake for both a low-key vacation and high-adrenaline adventure.

At 21,128 acres — three times its original size — Lake Arenal is Costa Rica’s largest lake. Known locally as Lago Arenal or Laguna de Arenal (Arenal Lagoon), the reservoir sits at the base of Arenal Volcano. In 1968, after 400 years of dormancy, Arenal Volcano awoke with a violent eruption, destroying several towns including the original Arenal and Tabacon. Today, their ruins are flooded beneath Lake Arenal, which was expanded in 1979 to generate hydroelectric power and drinking water. The reservoir is the golden child of Costa Rica’s hydroelectric power program; Lake Arenal generates more than 70% of Costa Rica’s hydropower – and 50% of the country’s electric power.

Straddling the provinces of Alajuela and Guanacaste, Lake Arenal is an aquatic paradise, attracting lake lovers from around the globe. Lake activities include swimming, kayaking, canoeing, boating, windsurfing, and fishing. In fact, Lake Arenal is recognized internationally as a mecca for inland anglers, and offers opportunities for solo and group fishing trips. Rent a boat and test your fish-finding skills, or hire one of Lake Arenal’s experienced fishing guides. You’ll troll for the world-famous and sharp-toothed guapote (rainbow bass), an incredible fighting fish that can exceed 15 pounds. Beneath the lake’s sparkling surface, rainbow bass are joined by populations of machaca, mojarra, catfish, South American bass, and tilapia.

In addition to fishing, Lake Arenal is well known for its excellent windsurfing and sailboarding. The reservoir’s average water temperature hovers at 72 degrees year-round, though ideal sporting conditions are from November through April, when high winds kick up around the lake. Beginner and advanced windsurfers will benefit from the lake’s boarding culture: experienced professionals offer lessons, gear rental, and plenty of camaraderie.

Surrounded by waterfalls, volcanic hot springs, caves, tropical rainforest and a picturesque, cone-shaped volcano, the Lake Arenal area is also ideal for exploration on foot. Hanging bridges offer a birds-eye view of the blue waters and startling Arenal Volcano cone, while private reserves around the lake form a web of hiking trails that pass near the reservoir’s shoreline. Outdoor aficionados, wildlife lovers, and birdwatchers are especially fond of Arenal Volcano National Park. The 30,000-acre park hosts pre-montane forest, lowland rainforest, cloud forest, and several other ecosystems. Common sighings include toucans, woodpeckers, coatimundis, howler monkeys, and sloths.

After a long day of hiking, fishing, or windsurfing on Lake Arenal, there’s nothing better than a relaxing dip in natural volcanic hot springs. Just a few miles west of the lake, several commercial hot springs promise gorgeous settings, varying water temperatures, and natural springs known for their healing powers. And when the sun goes down, tourists gather at the base of Arenal Volcano to watch the iridescent lava show; October is the best month for lava viewing.

Local lore has it that Lake Arenal is home to a 100-foot lake monster, though this cow-headed, horned, and serpentine beast is rarely seen and never photographed. Nearby Cote Lake, also called Lake Coter, is a mystical volcanic crater lake just west of Nuevo Arenal. The small lake, which boasts an excellent view down to Lake Arenal, is known for several UFO sightings, including one that was photographed by NASA.

After an exciting day, there’s no better place than your vacation rental’s lakeview porch. Lake rentals and real estate take advantage of the lake terrain, and are often perched atop green hills that overlook spectacular views. For a more urban setting, the town of La Fortuna (population approximately 7,200) is located a few miles east of the lake and provides a variety of tourism services, including hotels and bed and breakfasts. Tilaran, a small city of approximately 8,300 residents, is located four miles south of Lake Arenal’s western end. On the lake’s northern shore, between these two population centers, lies the picturesque town of Nuevo Arenal. Other small towns around Lake Arenal, like Aguacate, Las Piedras, San Luis, and Tronadora, are less populated.

With blue waters and even bluer skies, Lake Arenal is the sapphire jewel of Costa Rica. Excellent adventure activities, outdoor fun, and vacation opportunities await the thousands of tourists who visit each year. And for those looking for a Costa Rican home away from home, Lago Arenal has a growing expat population and booming retirement communities — so come find your vacation house, investment property, or retirement home today.

Things to do at Lake Arenal

  • Vacation Rentals
  • Fishing
  • Boating
  • Swimming
  • Canoeing
  • Kayaking
  • Whitewater Rafting
  • Hiking
  • Spelunking
  • Waterfall
  • Wildlife Viewing
  • Birding
  • National Park
  • Ruins

Fish species found at Lake Arenal

  • Bass
  • Catfish
  • Guapote
  • Machaca
  • Mojarra
  • Rainbow Bass
  • South American Bass
  • Tilapia

Lake Arenal Photo Gallery

  • View of Lake Arenal.

Lake Arenal Statistics & Helpful Links

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Lake Type: Natural Freshwater Lake, Dammed

Water Level Control: Instituto Costarricense de Electricidad (ICE)

Surface Area: 21,128 acres

Shoreline Length: 50 miles

Normal Elevation (Full Pond): 1,785 feet

Average Depth: 92 feet

Maximum Depth: 200 feet

Water Volume: 1,945,711 acre-feet

Completion Year: 1979

Lake Area-Population: 20,000

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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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