The Story Behind Lake Arenal

Before the middle of the 20th century, what we now know as Lake Arenal was just a small natural lake, gently fed by the Arenal River. It was surrounded by quiet farmland and the villages of Arenal and Tondadora—simple, rural communities where life moved at a slow and steady pace.

​

Everything changed after the powerful eruption of Arenal Volcano in 1968. The eruption brought devastation, but also raised important safety concerns for the people living nearby. In the years that followed, the Costa Rican government made a bold decision: to turn this region into a source of clean energy and water for the country’s future.

​

Between 1972 and 1976, a massive reservoir project was launched. An earthen dam was built, and slowly, over four years, the valley north of the volcano filled with water. What had once been fields and homes became a vast, shimmering lake—three times the size of the original.

​

In 1979, the Sangregado Dam was completed. Standing 88 meters tall, it raised the water level even more, creating the Lake Arenal we know today: Costa Rica’s largest lake, stretching over 85 square kilometers.

This transformation came with sacrifice. The original villages of Arenal and Tondadora had to be relocated. Their residents moved to a newly built town—Nuevo Arenal—designed to offer safety, infrastructure, and a fresh start.

​

Today, Lake Arenal is not only a key source of hydroelectric power (producing more than 150 megawatts), but also a beloved destination for adventure tourism, water sports, and nature lovers. It plays a vital role in irrigation, drinking water supply, and the vibrant local economy.

What began as a necessity grew into a symbol of resilience, innovation, and balance between people and nature—a place where energy, community, and beauty come together in one extraordinary lake.