Lake Arenal is a reservoir in Costa Rica, formed by enlarging an existing small lake of the same name by the completion of a dam in 1979. It is located near the Arenal Volcano and the Monteverde cloud forest. Lake Arenal is the key driver in a nationwide hydroelectric project that currently produces the majority of electricity for the entire country.^[1]. Water depth generally varies between 100 and 200 feet (61 m). The communities of "old" Arenal and Tronadora were submerged by the expanded lake.