Wednesday, August 6, 2014

What Did We Learn?

The more I learn,
the more I learn how little I know.
                                      - Socrates
The main goal of the first season of the Palenque Pool Project was to excavate and consolidate the largest pool in the Picota Group with the intention of better understanding its function and purpose (Video 1). The secondary objective was to evaluate and estimate the cost of consolidation of the Picota’s failing subterranean aqueduct that runs for 60 meters beneath the plaza floor. Below are some of the highlights pertaining to these questions.

The Pool

The Main Picota Pool, from the water’s edge, measures approximately 10 X 4 meters with an average depth of 1.25 meters, containing roughly 48 m3 (48,000 liters) of water. The Maya constructed the pool by excavating about 1.5 meters into bedrock, below the water table. Although the pool is within the water table (i.e. a fresh water source) it is also fed by two external sources, 1) a spring in the southwest corner; and 2) a subterranean conduit in the southeast corner (see Figure 1). There is also a constant source of water that bubbles up (out-gassing of CO2) from the pool’s floor (see Video 2). For the excess water, the pool maintains an overflow drain in the northeast corner that exits into main aqueduct (Figure 2).

Figure 1 - Map showing directional water flow.

Video 2 - Underwater in the Main Picota Pool.

Figure 2 - Interior of the overflow drain, northeast corner.
The feature’s east side is marked by a monumental staircase (Figure 3) composed of nine steps –five above water, one at the water’s surface, and three underwater – directing the participant to the pool’s floor. 

Figure 3 - Monumental Staircase of the Main Picota Pool.
The pool’s south side is double terraced, but unfortunately only small sections of the walls remain intact, with the collapsed portions now submerged. The west and north sides appear to only have a single terrace or wall.

The floor of the pool is comprised of a 10-15 cm layer of sand atop bedrock. The sand’s origin is unknown as Palenque is devoid of the material. Although it's possible the sand may be the result of the degassing (i.e. the bubbling) through the solid calcium carbonate on the bedrock floor. Analysis of the sand is currently underway.

Artifacts retrieved from the excavations consisted of a few broken matates, a mano, many kilos of pot sherds….oh, and one hippie crystal.

Function and Purpose

I’m fairly certain the pool’s true function and purpose will forever remain a mystery, but the first season did provide us with some insight. The pool’s location, in a large plaza only 8 meters from Palenque’s only standing stelae, does suggest that it was ceremonial in nature. Interestingly it’s quite similar to the Spring of San Juan in Chamula (Figure 4), just outside of San Cristobal. There the Tzotzil community uses the pool only once a year on May 3 for the Fiesta de Santa Cruz.

The nine stairs leading into the pool also indicate an element of ritual as this could be emblematic of the nine Lords of the Night (G1-G9). Let's also not forget that the pool is below the water table, it's actually underground.  The Palencanos may have viewed the pool as a symbolic (or actual) opening into the watery underworld – similar in the reverence held for the sacred cenotes of the northern Yucatan.

Lastly, if you refer back to the map from Figure 1 you will notice that all three pools in the Picota Group have conduits that bring water in and out of the aqueduct/stream. Now I'm sure there's a symbolic reason for combining the flowing water from the stream with the still water of the pools, but I haven't settled on an explanation for that just yet. However, over the last several months I did notice a functional reason for bringing water in and out of the pool – cleaning. Introducing water from the Picota Stream creates circulation, allowing for debris to easily exit via the overflow drain. Anyone who has ever owned a swimming pool is familiar with this concept. And no, we did not find a diving board or slide during our excavations.

Figure 4 - The Spring of San Juan in Chamula

The Picota Aqueduct

The main aqueduct that runs beneath the Picota Plaza is in dire need of consolidation. Many of the large capstones have fallen into the channel, essentially blocking the flow of water (Figure 5). When the Picota Stream is flowing at normal levels, this is not a big issue. But when a heavy rain occurs, limbs and leaf litter get hung up on the collapsed sections, preventing the water from flowing efficiently and thus causing the plaza to flood. We saw this happen after just one night of heavy rain in late-May (Figure 6). Luckily we were there to clear the debris out of the aqueduct, restoring normal flow. The erosion that occurs each time this happens is astounding. In less than two years over a cubic meter of erosion has taken place in just one area of the aqueduct (Figures 1 and 7).

Figure 5 - A collapsed capstones of the Picota Aqueduct.
Figure 6 - The Picota Plaza, flooded after one night of heavy rain.
Figure 7 - A heavily eroded section of the Picota Aqueduct.
The aqueduct is on the left, the eroded section is on the right.
The aqueducts of Palenque are a unique water management feature in the Maya world. They literally define Palenque’s ancient name, Lakamha', meaning Big Water. And the Picota Water Complex (pools, drains, and aqueducts) are all still operational…after some 1500 years without all still works! But not for long. Excavation and consolidation of the entire system will cost upwards of $400,000, but is essential for the preservation of this unique feature. In addition, test-pitting of the area in the 1950s and 1990s strongly suggests that the Picota Group is the earliest in Palenque. So needless to say, excavation of the Picota Plaza will no doubt yield enormous data on the early chronology of this ancient city – a subject we know little about.

What’s Next?

The planning for Season 2 has already begun with the writing up of season reports, analyzing data, publishing results, writing proposals, and dancing for money (not necessarily in that order). The plan is to return to Palenque in late-May of 2015 and begin excavating the upper terrace of the south side, as well as the west and north walls. More excavation will also take place on the floor of the pool.

So what did we learn? That the Picota Group’s water system is much more complicated (i.e. interesting) than previously thought. As with most my research I often think of the quote that is attributed to Socrates, "The more I learn, the more I learn how little I know." But isn't it fun?

The Picota Pool at the end of Season 1.

No comments:

Post a Comment