While it’s usually Yucatan’s lush, green jungles and pristine beaches that draw visitors’ eyes, beneath their feet, rivers, including the world’s longest underground river, flow through immense caverns. Thousands of years of rainwater percolation have carved these tunnels throughout the Mexican peninsula’s base material, ancient limestone coral reefs.
Not only have these underground waters sustained classic Mayan cities like Tulum and Chichen Itza, but they supply freshwater both to inhabitants and to more than 10 million annual visitors. They also receive their wastewaters. “These cave systems are so extensive and so interconnected that if there is a point of pollution in one area, then it can quickly get distributed to a very, very wide area,” British cave diver Stephen Bogaerts said in National Geographic.
Although Bogaerts has squeezed and scooted through miles of underground channels, his technique is slow motion compared to what Amigos de Sian Ka”an, a conservation group based in Cancun, is now attempting to do.
“This is quite spectacular—this is a very sophisticated study,” beams Gonzalo Merediz-Alonso, director. Amigos has joined with the Austrian Geological Service to adapt oil exploration technology to map underground aquifers. To do this, a Mexican Navy helicopter dangles a torpedo-like electromagnetic sensor as it flies in beelines back and forth across the peninsula, drawing a colorized map of subterranean waters.
“We can see how pollutants flow underground. We want to understand the hydrological system and to generate public policies to orient urban development in Tulum, for example. We certainly cannot establish a landfill on top of an underground water source,” Gonzalo explains. Considering that these black rivers eventually lead to the Caribbean, Amigos’ work wouldn’t just conserve drinking water, but reduce contamination of the barrier reef itself. Since the Mexican government plans on expanding hotel rooms by tens of thousands, torpedo speed may not be fast enough.