Its sources are located in between the
Sierra Madre and the
Sierra del Merendón mountain ranges in southern
Guatemala, near the town of
Olopa. The river forms a small part of the international boundary between El Salvador and Honduras. The river's
watershed covers of which , that is, 56.56% of the watershed territory, lie in El Salvador; in Honduras; and in Guatemala. 49% of El Salvador's territory is covered by the Lempa River basin, and 77.5% of the Salvadoran population lives in cities, towns, and villages located within the basin territory, including the capital city of
San Salvador. ==Hydroelectricity==