Access to water and modification of the landscape to enable water storage are key factors in assessing the viability and development of societies. Our civilization has already had its first wars over water (Tajikistan-Kyrgyzstan 2021-2022, genocides in Darfur 2003-2008, India just used access to water as a weapon in its fight against Pakistan). Explosions of dangerous bacteria in municipal water supplies get their five minutes in the media time and again (Legionella in Rzeszow in 2023, high-profile failures of treatment plants in Warsaw and Gdansk).
Every day we consume microplastic in bottles with the cap bravely attached, and the effects of the above and similar phenomena will only be able to assess historians and… archaeologists. The question of water quality turns out to concern not only our times, and its contamination may be one of the factors that determined the fate of ancient countries and perhaps even civilizations. An analysis of the ways in which the Maya transformed their cultural landscape using Stone Age technology reveals a thoughtful and sustainable impact on the environment.
Did and possibly how did the Maya deal with water contamination?
Studies of water reservoirs in Tikal (Peten, Yucatán, Guatemala) – reservoirs dug to aggregate water as far back as the Preclassic Maya – that began at the end of the first decade of the 21st century, yielded an astonishing and completely unexpected discovery. Taking cores from their bottom sediments, they sought data on water contamination by cyanobacteria. Meanwhile, in one of the reservoirs, a trace of an advanced water filtration system was encountered. The Corriental Reservoir – its name in Peten and southeastern Campeche means as much as a ravine – is located some distance from the ch’een, the ceremonial and residential center of the former city-state. The reservoir was not close to important palaces, pyramids and public squares. Yet it was in Corriental, not in any of Tikal’s other reservoirs, that traces of an installation used to filter water with cartridges filled with quartz sand… and zeolite were discovered!
The oldest treatment plant on the continents of the Americas?
Until now, it was thought that the oldest water filtration systems were developed in Europe and Asia. No similar installations have been found on the continents of the Americas. On the other hand, we still have little field-acquired data for Mesoamerica. To date, only a few dozen of the many thousands of ancient Maya reservoirs have been surveyed, and most excavations have been limited to a single test pit.
The Corriental reservoir was used for water collection from the Late Preclassic era (from around 200 BC) to the end of the Classical period (around 870-900 AD). It sustained a deficient population in the first centuries after the abandonment of the city. The zeolite filtration system at Tikal, identified by archaeologists, is therefore the oldest known example of a water purification facility in the Western Hemisphere and the oldest known case of zeolite being used to decontaminate drinking water on Earth.
Preclassic water reservoirs in Tikal
Beginning in 2009, three reservoirs were studied first: the Perdido (southwest of Mundo Perdido), the Temple Reservoir (between Mundo Perdido and the North Acropolis and Tikal Grand Plaza) and Corriental. Later, the study also included the Palace Reservation, located on the outskirts of the Central Acropolis, where the rulers and aristocracy of the state, known in pre-Columbian times as Yax Mutul, resided during Tikal’s hegemony over the Maya Plains.
A natural reservoir, the Inscriptions karst funnel, was also checked to compare the collected data. Each has its own and quite a large catchment area. All of the artificial reservoirs were excavated back in the Middle Preclassic era (around 500 BC), about two centuries after the dawn of Maya civilization at Tikal (the observatory-group E at Tikal is dated to around 800 BC, so it is among the oldest in the Maya Lowlands). These reservoirs have stratigraphic discontinuities due to dredging. All but the largest reservoir is Corriental. The chronology of the sites was determined by AMS radiocarbon dating of charcoal samples from contexts with undisputed stratigraphy.
In the centrally located Temple Reserve, the sediment layer reaches less than a meter. Perdido and Corriental are located a little further from the center of Tikal. The thickness in the former is 120 centimeters. The bottom of the reservoir was once sealed with limestone cement to retain water (Tikal is located in an area made of limestone, which naturally absorbs water, resulting in the scarcity of lakes and rivers). The thickness of the sediment at Corriental, which – unlike the others – was never dredged during use, is as much as 250 cm. Its bottom was composed of clay. The mineralogy of the sediments from the reservoirs and karst funnel was examined by X-ray diffraction (XRD).
A few words about stones…
Zeolite is a non-toxic, porous, hydrated aluminosilicate with natural adsorption properties. It owes these to its three-dimensional microcrystalline pores of 0.3-0.4 nanometer in size, which form a natural molecular sieve. It removes microbes, nitrogen compounds and soluble and insoluble toxins from water. Thus, today it has found many applications: from aquariums to neutralizing radioactive waste (e.g., after the Fukushima power plant disaster). Roman engineers used it as a filler in the construction of dams, harbors, bridges and aqueducts, without realizing its special properties.
There are about half a hundred types of zeolite occurring naturally, including analcym, mordenite and clinoptilolite. In Guatemala, analcym appears as a highly transformed form of jadeite. Mordenite and clinoptilolite are found in caves in western Guatemala, where active, dormant and extinct Sierra Madre volcanoes pile up. They also occur in association with quartz, calcite and smectite in places where volcanoclastic tuffs (rocks formed from ashfall after volcanic eruptions) are transformed into zeolites.
While the aforementioned calcite is the local Cretaceous-Paleogene limestone (the entire Yucatán peninsula was a great coral reef from the Cretaceous to the Pleistocene), quartz and smectite were born from the volcanic ash that makes up the Sierra Madre mountain range, also known as the Maya Highlands cultural area. Smectite is a clay mineral derived from the transformation of air-borne volcanic ash. In Tikal, therefore, not only cultural but also geological influences from both zones have mixed.
Although mordenite and clinoptilolite do not occur naturally in Tikal, they have been discovered in outcrops of crystalline tuff northeast of the city, where sources of clean drinking water also lie. The co-occurrence of macrocrystalline quartz, zeolite and clean water may have been a clue to the Mayans, the impetus for experimentation and subsequent use of the mineral. In Tikal, it has so far only been found at the Corriental site, where it occurs together with macrocrystalline (0.5-2.0 mm) quartz.
The microcrystalline quartz (0.05 mm) found in the sediments was formed as airborne volcanogenic crystals, also known as primary quartz. The ubiquitous co-occurrence of volcanogenic smectite and quartz octahedra in sediments from Tikal shows that volcanic ash fell here in portions throughout the city’s habitation.
Corriental
Corriental is one of Tikal’s largest water reservoirs. It has a capacity of about 57.5 million liters. It is surrounded by an embankment 4-7 meters high. In all the layers of sediment, we find shells of vessels that were used by the ancient Maya to scoop water. Only modest evidence of chemical contamination and no traces of cyanobacterial contamination were found here. According to the researchers, the filtration system here is an anomaly not only in Tikal itself, but also on the scale of the entire Maya Lowlands. The system consisted of clinoptilolite, mordenite and coarse to very coarse euhedral quartz crystals (the size of grains of sand). These zeolites and macrocrystalline quartz came from Cretaceous tuff outcrops exposed along the margins of the Bajo de Azúcar.
Bajo de Azúcar is a mid-forest floodplain located about 30 kilometers northeast of Tikal, the kind that abound in Peten today. These usually shallow reservoirs can grow to an area of several hundred square kilometers during the rainy season, making navigating the selva much more difficult. Especially since crocodiles take advantage of them. In the past, they were the basis of the Mayan civilization’s agricultural development, as they provided fertile soils. Crops were developed not only along their banks. Chinampas, or beds on the water, were built from the bottom sediments. However, Bajo de Azúcar at the time when the Mayan civilization flourished in the area of present-day Peten had to attract their attention with drinkable water.
The water filtration system probably took the form of a stone structure that supported filter cartridges placed in mats of reed or palm fibers, known as petates. The filtering material was, of course, zeolite and quartz crystals. Such installations operated above or within tributaries to the reservoir, which formed spontaneously during flash floods following tropical storms. Traces of such events include lenses of crystalline quartz in the reservoir’s sediments. Zeolite crystals, much smaller than quartz (0.001 – 0.01 mm), were more easily spread by water, so their presence in the sediments is more dispersed. Quartz alone would be able to optically clarify the water, but without the zeolite input, it would not clean the water of toxins and microbes.
From the beginning and to the end of time
The filtration system was in operation early, starting around 210 BC, during the preclassic period of the Mayan civilization. It was therefore six centuries older than the sand and gravel filter described in the Hindu treatise Suśrutasaṃhitā. It predates by some 2155 years the use of zeolite for water filtration by our much-advanced European civilization. To the inhabitants of southwestern Tikal, it provided healthy water for more than a thousand years!
It appears that the Maya made, through observation alone, an extremely important and interesting discovery. Whether and possibly why it was not applied more widely requires further research. Perhaps understanding the importance of what they had at their disposal, and applied only locally, could have protected at least Tikal, if not other city-states, from collapse(more on water contamination as one of the potential causes of the collapse of the Classic Maya civilization in the third part of the text).
The youngest, or stratigraphically highest, layer of zeolite in the Corriental reservoir is a reminder of the last episode involving the filtration system at Tikal. Scientists date it to the Late Classic era (at Tikal it was between 562-830 AD). The filtration system was apparently not renewed later. Thus, in the younger layers we find mercury from anthropogenic processes – the Maya used a dye containing this element to decorate palaces and temples. Mercury sulfide (cinnabar) was also used extensively in funerary rituals. Cinnabar rinsed from the walls and leached from burial sites in the catchment area landed in the Corriental reservoir, from which water was drawn.
It is not known why the Maya did not rebuild the filters or why they did not apply them to the other reservoirs on the site. Tikal was abandoned shortly thereafter, in the Late Classic era, around 870 AD, although the last Mayan traces associated with the Corriental reservoir are in the early postclassic years – 1010-1170 AD. – a time when Chichen Itza – one of the last, but paradoxically the most famous Mayan city – blossomed in the far north of Yucatán. The reservoir allowed the chosen few to survive a century or two after the collapse of the Classic Maya civilization.
Main Photo: Przemek Trześniowski Archeophotography