General information
on Lake Atitlan
Surface area: 126 km3 - 50 sq miles
Average depth: 203 meters – 126 miles
Maximum depth: 327 meters – 203 miles
Water volume 25.46 km3 - 6.1 cubic miles
Lake perimeter 101 km – 62.7 miles
Height above sea level: 1,564 meters – 5,131 ft
Average water temperature: 18C°
Water retention in the lake 78 to 110 years
Water level fluctuation: 12 meters – 39 ft in cycles of more than 30 years. There is evidence of a human settlement 15 metres underground that sank around 1,700 years ago.
Overview
Atitlan is the Nahuatl word that the Tlascalteco warriors brought by Alvarado gave the lake in 1524 and it means “near/in the water” (from “atl” water and “tlan” near/in). The name in K’aqchikel is “choi”.
Drainage
The lake has no surface drainage, but it does have underground outlets to the south coast via the San Lucas Bay and other sites south of the lake. The Quiscab River (in Jaibal), the Cojolya River (aka the Waterfall) and the San Buenaventura River in the San Buenaventura Valley, and the San Francisco River in Panajachel flow into it. In addition, the lake's waters come from several springs, mainly on the north side, and from rain that falls in its large basin (548 km2 / 212 sq miles).
Lake level fluctuation
Apparently, there are relatively long-period fluctuations in lake level; it was reportedly low in the 1820's, 10-15 meters higher in the 1870's, back down to its low level in the 1920's, and high again in the late 1940's and going down to the present. Most fluctuation is a result of variation in annual rainfall or the effects of regional earthquakes on the subsurface drainage from the lake; it is not known whether any uplift and subsidence of the caldera floor is involved. Short-term changes in lake level that are attributable to rainfall may be as great as the increase of 3.3 meters during the exceptionally wet year of 1933; those attributable to earthquakes may be as great as the drop of 2 meters that occurred within one month following the 7.5 Guatemala earthquake of 1976. Sediments of the lake floor suggest episodic, decades-long increases in thermal activity of fumaroles on the caldera floor.
State of the Lake
Being a deep lake means that life activity is concentrated in a strip about 80 meters from the shore. Until the late 1990s, the lake used to have remarkably clear waters with visibility of up to 15 meters (Secchi disc). Currently, due to human activity and the influx of pollutants, visibility is 5 meters. Normally, with the prevailing wind regime, the lake's waters are turned over every six months. In the middle of the lake, the waters are usually clearer.
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