Forecasting Algal Blooms with AI inLake Atitlán

Related to their photosynthetic activity, algal blooms produce pigments such as chlorophyll-a, which have a strong signal in satellite images, particularly in the visible and near-infrared parts of the electromagnetic spectrum. Hence, scientists can use a number of techniques, including spectral indices, to identify algal blooms. Algae rich water has been shown to have a peak in the green area of the electromagnetic spectrum, specifically in the 500 nm and 600 nm range (Jensen 2007). Satellite sensors (multispectral sensors) can measure light in those wavelengths, hence making it possible to detect quantities of chlorophyll-a produced by algae. Specific to Lake Atitlan, recent research shows that it is possible to use a spectral index derived from the ratio of blue to green reflected light as a proxy for the concentration of chlorophyll-a (Flores- Anderson et al. 2020). That research was done combining satellite images with field measurements, and show that it is possible to map the extents (area) of algal blooms in Lake Atitlan using satellite imagery - at least the area of the blooms near the surface of the water.

The communities surrounding Lake Atitlan depend on it - and its health - for their very livelihoods. Roughly 400,000 people reside in the communities surrounding the Lake. They depend on the Lake for their drinking water and roughly half of the people living around Lake Atitlan do not have access to treated drinking water. Therefore, for those people, any pollutants in the water can also affect their health. It is also believed that the algal blooms themselves have been triggered by an increase in untreated wastewater entering the Lake, and this is compounded by the destruction of natural ecosystems in the areas draining into the Lake. Lake Atitlan is also essentially at the center of a basin which only drains into it and has no outlets - what is referred to as an endorheic watershed. That means that chemicals from agricultural activities occurring in other parts of the basin will drain into and accumulate in the Lake. That will diminish the quality of the drinking water taken from the Lake, and is believed to cause algal blooms to flourish.

In the past, some of the wastewater draining into Lake Atitlan was treated, but the area’s only treatment plant was destroyed during Hurricane Stan in 2005, and four years later, in 2009, the first major algal bloom in Lake Atitlan was observed. The Lake is also the second most visited tourist attraction in Guatemala, and the algal bloom of 2009 resulted in a 25% decrease in visitation (Dix et al. 2012). For the sake of the health of those who drink water from the Lake, and the economic livelihoods of those depending on it, addressing algal blooms - and the broader water quality issue - is very important.

“Lake Atitlan is located in the Department of Solola, west of the Guatemalan capital, Guatemala City. It is located in an ancient volcanic caldera, bound by deep cliffs to the north and east, and by three volcanoes to the southwest. The Lake sits in a 541 km 2 endorheic drainage basin or watershed -meaning it lacks a surface water outlet. Those same endorheic characteristics accentuate the concentration of pollutants, sediments and other eroded materials, which accumulate in the lake. The management of lands within the watershed is therefore critical to the Lake’s health. Lake Atitlan also constitutes an important natural resource for tourism in Guatemala; populations totaling more than [400,000] surround it. For years, human activity within the Lake’s basin has been negatively impacting the Lake’s functions. Some of the most significant impacts are due to nearby municipalities dumping untreated sewage directly into the Lake. Intensive agriculture has also led to erosion, sediment transfer, and even decreased water infiltration into underground aquifers (Kogio, 1995). Kogio (1995) also notes that the percent of such infiltration in the Central Plateau has declined due to land use change, since most of the catchment area has been used for agricultural purposes.” - Hernandez et al. (2011)

Many communities around Lake Atitlan have been working hard to preserve this unique ecosystem and its provision of natural resources. There are also a number of governmental and non-governmental organizations and international cooperation programs working in Lake Atitlan, all committed to preserving the lake and its environment. Here, we present a brief list of these groups working at the forefront in Lake Atitlan:

Mancomunidades:

• Mancomunidad de Municipios T'zolojyá -MANCTZOLOJYA-
• Mancomunidad de Chichoy Atitlán –Mankatitlán-,
• Mancomunidad La Laguna -MANCLALAGUNA

NGOs and International Cooperation programs:

• “Vivamos Mejor” https://www.vivamosmejor.org.gt/sitio/en/
• Centro de Estudios y Cooperación Internacional -CECI-
• Asociación Amigos del Lago https://amigosatitlan.org/home/
• Movimiento Ciudadano Mas Vale Limpio https://www.facebook.com/masvalelimpio
• Afica 70 (cooperacíon Italians).
• Asociación de Desarrollo Comunitario del Cantón Panabaj -ADECCAP https://ethelramirez.wordpress.com/acerca-de/
• SOCDEVI ,
• GIZ, Asociación Atitlan https://www.giz.de/entwicklungsdienst/en/html/59987.html

Government institutions:

• CONAP https://conap.gob.gt/
• MARN https://www.marn.gob.gt/
• AMSCLAE https://www.amsclae.gob.gt/
• INAB https://www.inab.gob.gt/
• SESAN https://www.sesan.gob.gt/
• MAGA https://www.maga.gob.gt/