Culture and Ecology of Chaco Canyon and the San Juan Basin

Chapter FiveThe Florescence of the Chaco People:The Classic Period (Pueblo II to Early Pueblo III)The climax of this development was Pueblo Bonito. From the treasures found within its ruinedwalls we can reconstruct the golden days of Pueblo history. Bonito housed somewhere around1,000 people and there must have been 3,000 to 4,000 people in the canyon living in the othercommunal dwellings. To Chaco came the riches of the Pueblo world through an extensive tradesystem. Shells from the west coast and the Gulf of Mexico, pottery from the neighbors on all sides,parrots and copper bells from old Mexico, and various Jl'Iineral pigments and semi-preciousturquoise came from the four comers of their far-flung country. (Pierson 1956: 15)Most of what was known about Chaco Canyonprior to 1969 was derived from excavations at severallarge pueblos and a number of smaller sites dating tothe Classic period (Appendix A). Summaries of earlyresearch by Brand (1937a) and by Gordon Vivian andMathews (1965) provided overviews of the natural setting,environment, and resources available, as well asthe known changes in architecture and material culture.Based on available tree-ring samples, Bannister(1965) found considerable unity among dated sitesranging between A.D. 828 and 1178, a period he considered"Classic" and one that encompassed what arenow defined as Late Pueblo I through Pueblo III sites(see Appendix B for a correlation of chronologicalschemes used during different studies). Cessation ofthe construction of large pueblos and a dwindling ofthe population were thought to have occurred by themid-A.D. 1100s. Several possible reasons for thisflorescence and decline have been proposed.Why this florescence and decline occurred in asemiarid environment needed explanation. AlthoughKidder (1924) painted a bleak picture of ChacoCanyon and its surrounding area, Gordon Vivian andMathews (1965:1-5, 14) recognized its uniquenesswithin the central San Juan Basin, in that perennialgreen cover existed in side canyons where there werepockets of trees and other vegetation not found on thecanyon floor or flat plains to the north and south.Although the greatest variation in vegetation andlargest number of species were found in these sidecanyons, they were not necessarily representative ofthe entire area. Based on the presence of a few localpine trees (Hawley 1934; Judd 1954) and estimates ofbetween 75,000 and 100,000 trees used in constructionof Chetro Ket!, Vivian and Mathews(1965: 110) suggested that a widespread pine beltprobably receded as construction needs increased.Comparison of 32 years of precipitation records withhistoric Hopi agricultural needs (Hack 1942) indicatedthat the growing season, calculated at 150 days, waslong enough, but the average annual precipitation of22 cm (8.71 in) in Chaco was about half of the 47.5em (16 in) needed to produce Hopi com. Thus, unlessadditional water was captured, dry farming would betenuous at best. Floodwater farming, enhanced bycapturing runoff from north side mesas using watercontrol features, however, would increase availablewater. Evidence for water control features had beenrecorded by a number of investigators (Brand 1937b:113-114; Bryan 1954:38, 39; Hewett 1905, 1936: 123-125; Holsinger 1901; Judd 1954:55-57). Floodwaterirrigation and akchin fields were therefore consideredthe most likely farming methods used. Based onphysiographic features, locations of the former on thenorth side of the Chaco Wash and the latter on thesouth side were postulated. Gordon Vivian began astudy of aerial photographs to determine where canals