Water storage spurred growth of Maya cities.

Water storage spurred growth of Maya cities

An oasis on a parched savanna draws a crowd of thirsty animals. That same principle applies on a much grander scale to the emergence of "Classic period" citystates in the Maya lowlands between A.D. 250 and A.D. 900, say anthropologists who have reexamined detailed maps of one such site.

The ancient Maya city of Tikal, in northern Guatemala, lacked a permanent water source such as a river or spring, as did other lowland sites in Guatemala, southern Mexico, Belize and Honduras. To provide water throughout the four-month annual dry season, residents constructed reservoirs fed by clay-lined drainage ditches, report Vernon L. Scarborough of the University of Cincinnati and Gary G. Gallopin of the State University of New York at Buffalo.

Tikal's reservoir system proved a liquid magnet for lowland inhabitants struggling with yearly droughts, and the city's population peaked at 60,000 to 80,000 around A.D. 750. Indeed, Scarborough and Gallopin argue in the Feb. 8 SCIENCE, the ability to control water critically influenced the growth of most lowland Maya cities, as well as the emergence of political control by an elite class serving Maya Kings.

At many of these lowland Maya urban centers, spurts of population growth followed by temporary abandonment probably corresponded to fluctuations in annual rainfall and the availability of stored water, adds anthropologist Richard E.W. Adams of the University of Texas at San Antonio, in a commentary accompanying the research report. Adams asserts that the lack of sufficient water reserves in times of drought, rather than military or political conflict, may have caused the permanent abandonment of the earliest lowland cities, such as Nakbe (SN: 1/27/90, p. 57).

Scarborough and Gallopin reconstructed Tikal's reservoir system from previously published maps of the ancient city. Six groups of paved drainage systems fed water into at least 10 central reservoirs, they maintain. The researchers estimate that the reservoirs received at least 900,000 cubic meters of water annually through the drainage setup, suggesting a far greater waterstorage capacity than previously thought, Adams points out.

The controlled release of water from central reservoirs into smaller storage basins on the outskirts of Tikal would have supported year-round crop cultivation, the investigators note, although it remains unclear how the Maya released water from the central reservoirs.

Central Tikal also contains "residential reservoirs," apparently intended to store water for individual households. A few small reservoirs were attached to domestic residences, but none of these received water from the central reservoirs, the researches say.

Massive building projects toward the end of the Classic period created quarries that may also have served as reservoirs and helped promote Tikal's growth, Scarborough and Gallopin suggest. In areas with seasonal water shortages, reservoirs acted as an underrecognized spur to urban growth, they conclude.