The lake was originally much smaller than it is today. The size was approximately 20-30% of its actual size. It was naturally created approximately 2-3 million years ago in the valley next to the mountain range. The small lake was irrigated by a couple of rivers.
In the ‘70’s the Government of Costa Rica was looking for a place to possibly build a Dam and produce electricity using water as the country had to buy petroleum to produce electricity and the cost was high for a small country.
In the '70s the government started to build a hydroelectric project in which the lake will be the main part of it. So the Costa Rican Institute of Electricity started the project in 1974.
To start the project some towns close to the lake must be relocated, this was the case of Tronadora and Arenal. The government offered the inhabitants to buy their lands or be relocated to higher ground and those who have no properties in town could have one and pay it later.
Finally, in 1978 the hydroelectric project Lake Arenal was finished, the last element was the completion of the Sangregado dam, with 1,012 meters long, with a maximum thickness at the base of 553 meters and 8 meters of the crest, the height is 65 meters and today the route number 142 crosses this dam, this way connects La Fortuna Town with Nuevo Arenal Town, and also we could say that connects Alajuela Province with Guanacaste Province.
With the passage of time, locals call it Arenal Dam. Around 4.6 million cubic meters of construction material were used to build it and the approximate cost of the project was about 1.500.000 colones of those days.
The hydroelectric project is producing today approximately 10 to 12% of the total electricity of the country, and around 35 to 40% of the hydroelectric energy.
Arenal Lake is also a wetland or part of it. In this case, the lake hosts multiple species of animals and flora that belong or live in this kind of habitat. As it adjoins the National Park this lake also turned into a valuable life zone combining mountains, rivers, and the lake and serving as a home for local tropical birds, reptiles, mammals, and fish of course.
Nowadays the Arenal Lake is one of the top attractions in La Fortuna. Many people come to this lake to practice kayaking, fishing, windsurfing, sailing to the sunset, or have some fun with jet skis or boats.
Local tour operators perform several tours to sightseeing the surroundings, there are great views of the Arenal Volcano and the mountains around which is in simple words a paradise.
Also, the lake is a very used connection between tourist destinations of La Fortuna and Monteverde, as many tourists navigate it every day to cross from one place to the other, in a faster and more scenic way than going only by land.
We recommend taking the Kayaking Tour at the lake, where you can spot lots of wildlife and the majestic view of the volcano.
Important data of Lake Arenal:
Lake Arenal has an area of 87.7 square kilometers.
It stores 2,416 million cubic meters of water and reaches 546 meters above sea level.
Maximum length 30 Kilometers
Maximum width 4 kilometers
Waves are generated up to a meter high
Rivers that supply it: Arenal, Aguas Gatas, Caño Negro, Chiquito and eight small rivers.
Electricity generation 157,398 KW.
It is the largest artificial lake in Central America.
The waters of the Arenal are used for recreation, fishing, and as a tourist destination.
The water that comes out is reused in the Miguel Dengo hydroelectric plant and as an irrigation system.