Water Management and the Political Economy of Chaco Canyon During the Bonito Phase (ca. AD 850–1200)

Abstract

Agricultural intensification is widely assumed by archaeologists to have been a catalytic factor in the development of social complexity in Chaco Canyon, New Mexico, between ca. AD 850 and 1200. In this perspective, water control technology resulted in surplus food production which was controlled by elites to finance the construction of massive buildings (“great houses”). However, recent fieldwork and archival research has been unable to substantiate this view of technological innovation promoting surplus agricultural production. An alternative explanation for economic growth is social transactions involving labor rather than food.

La intensificación agrícola es ampliamente asumida por los arqueólogos como un factor catalítico en el desarrollo de la complejidad social en Chaco Canyon, Nuevo México, entre el 850 y 1200 DC. En esta perspectiva, la tecnología de control del agua resultó en un excedente de producción de alimentos que fue controlado por las élites para financiar la construcción de edificios masivos (“casas grandes”). Sin embargo, trabajos de campo recientes e investigaciones archivísticas han sido incapaces de corroborar esta perspectiva de la innovación tecnológica que promueve el excedente de producción agrícola. Una explicación alternativa para el crecimiento económico son las transacciones sociales que implican trabajo más que alimentos.

Keywords:

• Chaco Canyon
• Great houses
• Agricultural intensification
• Water control
• Surplus production

Acknowledgments

R. Gwinn Vivian’s pioneering work and gracious professionalism are inspirational. His extensive field studies of Chaco water control created a legacy of empirical data and theoretically informed models that are the foundation for any consideration of great house economy and while my thesis about water control is at odds with Gwinn’s view of managerial complexity, that in no way diminishes my immense regard for his research and ideas or my support for his vision of Chaco as a prime agricultural zone in the past. The rigorous experimental investigations of William B. Gillespie, H. Wolcott Toll, Mollie S. Toll, and Marcia Newren have provided the only quantifiable field data for maize productivity in Chaco based on actual yields. The efforts by these National Park Service Chaco Project staff members in the 1970s to understand how water control features actually functioned through hydrological engineering studies and cultivation of experimental plots generated invaluable insights about the scale and nature of runoff irrigation. I believe the ongoing fieldwork by the University of New Mexico is building upon a foundation established by Chaco Project archaeologists.

I am very pleased to recognize a number of colleagues who provided information or access to unpublished materials, especially Ruth Van Dyke, Wendy Bustard, Dabney Ford, Brenna Lissoway, and Roger Moore. Many current and former University of New Mexico faculty and students have been integral contributors to ongoing field and laboratory research, especially Patricia Crown, Wetherbee Dorshow, Lee Drake, Jennie Sturm, Beau Murphy, Pablo Flores, Marian Hamilton, Joe Birkman, and Jacque Kocer (who also translated the abstract into Spanish). None of these fine people is responsible for any errors or confusion in the text. Two anonymous reviewers offered important critiques and bibliographic guidance. Financial support has been provided by the National Science Foundation (BCS 1523224) and the Colorado Plateau Cooperative Ecosystem Studies Unit (#H1200-09-005).

Data Availability Statement. Primary site information is available at the Chaco Culture National Historical Park Archives, University of New Mexico, Albuquerque.

Supplementary Material

For Supplementary material accompanying this paper, visit 10.1080/00231940.2017.1343109.

Notes

1 In agrarian societies with strong ancestor cults, as among the modern Pueblos, we should expect that ancestors were central actors in social organization and religion and were literally enmeshed in the daily lives of communities. It is only from our perspective as researchers that ancestors are perceived as merely symbolic or conceptual entities.

2 The factors that caused the Bonito paleo-channel to form are unknown (Hall 2010b). Force et al. (2002) suggest that a gypsum sand dune at the mouth of the canyon controlled base levels by periodically damming floodwaters, but this model has been challenged by field studies that found no evidence for ponding (Love et al. 2011; also Hall 2010b). The paleo-channel formed and filled during the North American Medieval Warm Period (ca. AD 900 to 1300) when average temperatures in the Southwest were about 1°C higher than the average for the past 1,200 years, and a severe drought occurred in the mid-AD 1100s (Woodhouse et al. 2010). However, as a number of researchers have concluded, the AD 900s on the Colorado Plateau were mostly characterized by average annual rainfall (there are no reliable measures of summer precipitation), but the AD 1000s with higher-than-average precipitation (Bocinsky et al. 2016). During the tenth century there was extensive aeolian deposition around Pueblo Bonito and an apparent hiatus in construction activity (Judd 1964; Lekson 1984; Windes and Ford 1996) that may signal a period of aridity. Unfortunately, there is no conclusive linkage between regional climate patterns and the Bonito paleo-channel history (Dean and Funkhouser 2002) and arroyo formation is demonstrably complex with respect to climate, which is why localized stochastic events (such as a single massive storm) may play critical roles (Huckleberry and Duff 2007).

3 In this paper a number of feature types are presumed to be associated with the physical control and management of flowing water: canals are man-made channels designed to irrigate fields; headgates (or floodgates) are conduits that can be opened or closed to regulate water entering a field system or reservoir; fields are areas in which plants were intentional cultivated; dams are features built to retard or block flowing water; reservoirs or rendition features are artificial constructions intended to hold water blocked behind dams; weirs are small, often temporary barriers that divert surface flows from natural pathways.

4 Detailed survey information for sites in Chaco Culture National Historical Park can be found at the Chaco Research Archive (http://www.chacoarchive.org/cra/) but site locations are not indicated in Figure 3 at the request of the National Park Service.

5 In the early 1980s the National Park Service Chaco Project re-excavated the Rincon 4 headgate complex under the direction of William Gillespie, who drew new maps and recorded local stratigraphic sequences. Headgates were then left open so that they could be used to water experimental maize plots in likely farming locations and a new 30-m-long feeder ditch was excavated to the west to bring water into the gate complex (Toll et al. 1985). The headgates were documented channeling water after a thunder storm by a film crew and featured in the 1980 NOVA film “Chaco Legacy.” Compared to other experimental locations in the canyon, the Rincon 4 fields were less productive, particularly compared to nonirrigated dune plots on the south side of the canyon and the investigators speculated that perhaps great temperature extremes were the cause (Toll et al. 1985:112).

6 Estimates derived from published photographs and a National Park Service map (c55411).

7 Ceramic identifications from headgate excavations in the 1970s made by Robert Buettner indicate that the Rincon 4 complex, the Casa Rinconada Complex, and the Chetro Ketl complex were overwhelmingly dominated by Chaco black-on-white (ca. AD 1075–1150) and McElmo black-on-white (ca. AD 1075–1250). Mesa Verde black-on-white (ca. AD 1150–1280) occurred in excavations at Casa Rinconada, Chetro Ketl and Hungo Pavi. Gallup black-on-white (ca. AD 980–1150) was rare. (Time spans from Office of Archaeological Studies Pottery Typology Project website at http://ceramics.nmarchaeology.org/typology).

8 Tankersley et al. (2016) report two sediment cores from this feature but the exact locations are not given. The reservoir was breached prehistorically and all sediments behind the dam are a combination of recent deposition combined with organic material from use historically as a Navajo corral. Although the authors suggest the reservoir was used to distribute water to fields there is no empirical evidence for this conclusion and it is difficult to imagine much cultivation on the exposed bedrock below the reservoir, although there are excellent field locations on the mesa above.

9 The third largest discharge event recorded in Chaco was a January rain-on-snow runoff-flow of 35.7 m3/sec (Love et al. 2011:110).

10 Most maps showing Chacoan great house locations do not indicate relative size of these structures and hence convey the impression that all structures are the same. In fact, the combined mass of most (and perhaps all) San Juan Basin “outliers” would not be equivalent to the Chetro Ketl great house in the canyon.

Additional information

Funding

This work was supported by National Science Foundation: [Grant Number BCS 1523224]; National Park Service, Colorado Plateau Cooperative Ecosystem Studies Unit: [Grant Number H1200-09-005].