The western basin receives pollution loads from the capital as well as from the whole catchment area via the Villalobos River. This are annually approx. 75,000 tons of dissolved wastes, also fertilisers, causing high eutrophication. Another fact is that this river brings around 500,000 tons of sediment to the lake, as a result the depth of the lake diminishes about 70 cm per year. The water of this basin is drained by the Michatoya River, which is used for hydroelectric power generation.
Most important threats are:
- High population growth
- Deforestation for firewood
- Intensive farming at the shore line
- Industrial growth in the catchment area and the wastewater contamination
The Lake Amatitlán with its surrounding valleys, mountains and volcanoes has a unique landscape, which is used by many people as recreation area.
There are archeological remains dating back to the year 2000 B.C.. The town of Amatitlan was founded in 1536 and developed quickly. Since the colonial time, the lake is a centre of fishery. Its catchment area was the most important site of cochineal production (E 120), which was the main product for export when industrial chemicals had not yet replaced the natural dye. The lake water is also used for domestic use, irrigation and industrial activities. In 1800, the average depth of the lake measured 33 m, in the year 1996 the depth was only 18 m.