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Rising Waters at Lake Atitlan

Concrete roof of a building flooded by rising lake level

Lake Atitlan from San Pedro

I am presently living with my family in Panajachel, on the shores of Lake Atitlan in Guatemala. Lake Atitlan occupies a volcanic caldera that formed in a huge eruption about 80,000 years ago. The lake is about 20 km long, 10 km wide and 300 m deep, so even very simplistic volume calculations indicate a large volume of erupted material draping the surrounding region. There are villages scattered around the shore of the lake, wherever there is a foothold between the shore of the lake and the bounding cliffs.

Village on shore of Lake Atitlan. Note the corn fields on the caldera wall above.

One of the unusual features of Lake Atitlan is that while it is the center of a considerable watershed it has no surface outlet. Rainfall and surface streams flow into the lake, but outflow is only through groundwater flow that discharges to springs on the Pacific slope. Thus while the inflow to the lake is quite variable depending on weather conditions and especially the occasional hurricane that crosses the region, the outflow remains constant. In consequence the lake level is quite variable; during extended dry periods the lake level falls and during periods of higher than average rainfall the lake level can rise.

After decades of low and relatively stable lake levels, Lake Atitlan rose 3 meters in 2010, and another 2 meters this year. In other words the lake level has risen 15 vertical feet in the last 2 years! This has caused major problems for people living along the lakeshore. Everywhere one sees drowned houses and dock facilities, eroding banks, and flooded shorefront property.

Buildings flooded by rising lake level, San Pedro on Lake Atitlan

Concrete roof of a building flooded by rising lake level

But it makes a great diving board...

Interestingly, the last lake level high stand (in the 1960’s as best as I can tell) is well within the memory of the older residents, but still people built on the lower shoreline with apparently little regard for the fact that the lake level might change. It’s not only in the U.S. that people have short functional memories!

Flooded farmland on shore of Lake Atitlan

David Greene

3 Comments

  1. Don’t build on the lakefront. Build on an overlook. At San Marcos La Laguna, people told me that the natives don’t set themselves on the lakefront, only the tourist types do.

  2. A drainage tunnel would certainly do the job, but might be quite difficult to build since water is already percolating through the rock. A siphon system might be better since part of the crater wall is relatively low, with a long slope down to the Pacific for “pull”. Still be a big project, though.

    Apparently, earthquakes can change the outflow rate dramatically, as well. After the 1976 Guatemala City earthquake the lake level dropped by more than a meter, presumably because the groundshaking opened up new fractures for the water to drain out through. But no one here would wish for another earthquake like that one!

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