The watersheds of the Tacaná volcano, which stands at an altitude of 4,093 m, cover a transboundary area of 3,170 km² right in the middle of the border area of the Department of San Marcos, Guatemala and the State of Chiapas, Mexico. This area comprises the Coatán, Suchiate, Cosalapa and Cahoacán rivers. The Coatán and Suchiate watersheds originate on the volcano, with both shared by Guatemala and Mexico. Cahoacan and Cosalapa are subwatersheds of the Coatán River, within Mexico.

The climate in this area is warm and temperate with an average temperature of 13.9°C. The driest month is February (6 mm) and the wettest one is June (268 mm). The average rainfall in the study area is 1413 mm.

These watersheds are of great strategic importance for both countries since they supply water to a large number of residents in the cities located downstream and are the main source of irrigation water for agriculture. In the lower reaches, fishing is an important source of income. However, deforestation and degradation of the upper watersheds and of riverbanks has led to erosion and flooding and reduced capacity of the watersheds to absorb water. (IUCN 2012)