Noel Avalos ran to the shore of Lake Suchitlán and found thousands of dead fish washed up overnight. Nearly a year later, Salvador still has no explanation for what caused the die-off, and the lake’s pollution has spread into daily work and income around Copapayo.
The lake is El Salvador’s largest body of freshwater, a Ramsar site, and the country’s main hydroelectric reservoir. It supports 12 of El Salvador’s 14 native fish species and feeds the Cerrón Grande dam, which supplies roughly 28% of El Salvador’s hydroelectric power.
Copapayo and Suchitoto
Around the lake, fishers earned about $15 a day before the crisis deepened. Residents who depend on fishing reported that livelihoods were deteriorating, while local guides said tourism fell as the water turned opaque and foul-smelling.
Alberto Castillo, a boat operator in Suchitoto, said: “The clean-up seemed impossible.” He added: “People are starting to come back very slowly, but during these months we had to take different jobs, getting only 30% of what we were making before.”
Labtox and the water
In the weeks after the die-off, researchers from the University of El Salvador’s toxicology laboratory were asked to analyse the water through institutional channels linked to the courts. Labtox provides technical support without publishing public reports, leaving the lake’s condition to be read through what people see on the surface.
By August 2025, nearly 70% of Lake Suchitlán’s 135 sq km surface was covered with water lettuce, and plastic waste had accumulated along the shoreline. Fish died, mosquito numbers surged, and persistent foul smells rose from the water.
El Salvador and Cerrón Grande
Scientists and local environmental organisations had warned for years that untreated sewage, agricultural runoff and weak water-quality enforcement were pushing the lake toward collapse. Gabriel Cerén said the nutrient overload was severe, and he explained: “What facilitates the reproduction [of the water lettuce] is the high amount of nutrients that the Lempa River gets from fertilisers that end up in the lake and concentrates a high amount of nitrogen and sulphates,”
The contradiction is hard to miss: Lake Suchitlán carries national weight for electricity, fisheries, tourism and biodiversity, yet the cause of the die-off still has no public explanation. That leaves fishers in Copapayo, boat operators in Suchitoto, and other lake users waiting on the same unanswered question: what caused the pollution, and what did the water analysis find?
