As part of its Perpetual Planet initiative, Rolex has supported the Xunaan-Ha Expedition, with its twin goals to explore cave systems and find sources of contaminated water in Yucatan’s giant aquifer.

In November 2021, a team of professional divers, led by one of the world’s most experienced underwater explorers, Robbie Schmittner, completed a two-week expedition into the sinkholes of the Yucatán Peninsula to chart the cave systems and sample water quality at nine sites.

Support for this project through the Rolex Perpetual Planet initiative goes to the heart of the commitment the brand has made to future generations, by championing individuals and organizations in science-led efforts to preserve the natural world and the systems that sustain life. 

Schmittner has spent more than 20 years in the region exploring the Yucatán’s labyrinthine cave systems and studying the drainage system across the peninsula, which has no rivers and lakes. Instead, rainfall seeps through the porous limestone and collects in an aquifer that is the region’s only source of fresh water.

POLLUTION IN THE AQUIFER
The German cave diver’s ambition is to provide the scientific basis for tackling pollution of the aquifer, one of the world’s largest. It stretches 165,000 km2 across the Yucatán Peninsula, all the way to Guatemala and Belize. With a regional population of some 2.3 million people that swells by some 6 million tourists annually, pollution of the aquifer is a growing threat. Most of the effluent finds its way into the aquifer through overflowing septic tanks and open dumps with very little, if any, treatment in any of the cities.

“Tourism is the only real industry in the region as the soil is too poor for agriculture. But development on the peninsula has nevertheless taken place, using fresh water from the aquifer without much regard for its fragility and vulnerability,” according to Schmittner.

“A better understanding of the natural drainage system is essential for protecting ecosystems – the savannah, the rainforest – that depend on the aquifer for water,” he says. “Independent scientific projects, such as for the protection of the jaguar and mangrove forests, the preservation of the nature reserve areas or the replanting of coral reefs, would be much more efficient if the course of the groundwater was known, as in some cases it also comes with deadly pollution. We need to find the sources of contamination.”

One of the expedition’s achievements was to add 3,214 m to the roughly 1,600-2,000 km of cave systems already explored. This is an impressive distance given the winding nature of the caves that present their own set of risks. Divers use a thin nylon cord to prevent being lost but they can often get stuck in small caves. “If you get in, you can get out,” he says. “But it is stressful.” 

For Schmittner, one of the most important discoveries was to find cave systems that added valuable data on how rainfall drains across the peninsula.

Fresh water collects in the aquifer and sits above the saltwater that seeps in from the Caribbean because it is less dense. However, it continues to find ways to escape and is redirected through fractures or faults and waterbearing caves in the limestone plateau as it makes its way towards the ocean.

Using information from satellite images, cave exploration and an understanding of inland and ocean currents, Schmittner has formulated a big picture of the drainage system. “Viewed as a fact that the principal fractures are related, it is possible that most of the precipitation collects and is directed to the Caribbean coast in the fractures and their cave systems,” he says. “Massive suction is caused by powerful currents from South America that are dramatically constricted as they pass the Yucatán Canal on their way to the Gulf of Mexico. This draws fresh water from the Holbox and Akumal fractures, which run close to the Caribbean coast, where the limestone is comparatively thin, and draws it up to the north-eastern tip of the peninsula. This is how 2,000 km of cave passages were created along the Caribbean coast.”

As a result of the expedition, the geology, hydrology and chemistry of the cave systems will be analysed by university departments in Mexico and the United States. 

The next step for Schmittner is the construction of a Water and Jungle Institute in Tulum, which he will run. It will provide education, research, consulting and advice. “Masters and PhD students will conduct research there, with implications globally as aquifers in coastal and arid regions are under threat,” he says. “We need to preserve them for generations to come.”