Scientists have identified the largest ancient Mayan dam, constructed from stone and holding back around 20 million gallons of water in a man-made reservoir.
The Tikal dam stretched more than 260 feet in length and was 33 feet high, and sheds new light on how the Maya conserved their natural resources for over 1,500 years.
"The overall goal of the UC research is to better understand how the ancient Maya supported a population at Tikal of perhaps 60,000 to 80,000 inhabitants and an estimated population of five million in the overall Maya lowlands by AD 700," says University of Cincinnati anthropologistVernon Scarborough.
"That is a much higher number than is supported by the current environment. So, they managed to sustain a populous, highly complex society for well over 1,500 years in a tropical ecology. Their resource needs were great, but they used only stone-age tools and technology to develop a sophisticated, long-lasting management system in order to thrive."
To cope with seasonal and extended droughts, the Maya carefully integrated the built environment - expansive plazas, roadways, buildings and canals - into a water-collection and management system.
At Tikal, they collected every drop of water that fell onto these paved or plastered surfaces and sluiced it into man-made reservoirs.
The gravity dam is the largest hydraulic architectural feature known in the Maya area, second in size only to the huge Purron Dam built in Mexico's Tehuacan Valley sometime between AD 250-400.
For a long time, it was considered primarily a causeway - one that tourists coming to the site still use today. But the team's research now shows that it did double duty, and was used as an important reservoir dam as well as a causeway.
To help purify water as it sluiced into the reservoir tanks via catchment runoff and canals, the Maya employed deliberately positioned 'sand boxes' that filtered the water as it entered into the reservoirs.
"These filtration beds consisted of quartz sand, which is not naturally found in the greater Tikal area. The Maya of Tikal traveled at least 20 miles to obtain the quartz sand to create their water filters," says UC's Nicholas Dunning.
"It was a fairly laborious transportation effort. That speaks to the value they placed on water and water management."