Lake Alajuela, reservoir in Panama

Lake Alajuela is an artificial reservoir in the Chagres River basin, formed in 1935 by the Madden Dam and linked to the Panama Canal. The Chagres, Pequení, Boquerón, Salamanca, La Puente, Indio, Piedras, San Cristóbal and Escandaloso rivers flow into it. Its waters supply 45 percent of the canal's total water.

The lake was created in 1935 to store and manage water for the Panama Canal system. Originally called Lake Madden by American administrators, it was renamed when Panama regained control of the canal zone.

Official Panama Canal sources spell the name Alhajuela, with an intercalated h, while most outside media write Alajuela; 19th-century maps show the nearby settlement was called Alhajuela. The reservoir was known as Madden Lake during U.S. administration of the Canal Zone and was renamed after control returned to Panama.

The lake lies in the Chagres River basin, with the Madden Dam at its edge and the Panama Canal to the southwest. Access is mainly by road from Panama City; no tourist facilities or marked trails are documented. Water levels vary greatly, from the record high of December 2010 to the low levels of August 2023.

The name Alhajuela, with an intercalated "h", is the form used by official Panama Canal sources, while most outside media write Alajuela; 19th-century maps show the nearby settlement was called Alhajuela. In late August 2023 the lake stood at its lowest level in recent years, limiting Panama Canal traffic.