Lake Amatitlan (amatl = letter, titlan = mail in the pipil language) is the fourth largest water body in Guatemala, located close to the south of the capital city (ca. 15 km) at an altitude of 1,188 m above sea level. The lake consists of two basins connected by a narrow constriction, where a dry dock was constructed to let the railway pass through. This separated the lake into two water bodies with different physical, chemical and biological characteristics. The western basin receives all pollution loads coming from the southern part of the capital city as well as from the whole catchment area via the Villalobos River. The water of the same basin is drained by the Michatoya River, which is used for hydroelectric power generation.

The lake is directly and negatively affected by the rapidly growing impacts from the capital area, through 1) population growth, 2) consumption of forest trees for fuel, 3) inadequate land use, 4) industrial development in the catchment area, 5) lack of environment consciousness and environmental education among the inhabitants, 6) almost no administrative/legal control for environmental protection, and 7) absence of proper foresight and management program.

Despite these circumstances, L. Amatitlan and surrounding valleys, mountains and nearby volcanoes present a unique landscape, making the area a recreation park for a lot of visitors. The lake has also been used in other multiple ways. In pre-Columbian days, it was a place for rituals where offerings were deposited. During the colonial times, the lake was a center of fisheries and its catchment area was the most important site of production of cochineal, which was the main product for export when industrial chemicals had not yet replaced the natural dye. The lake water is also being used for domestic use, irrigation and industrial activities (13, 28, 29).