Culture and Ecology of Chaco Canyon and the San Juan Basin

182 Chaco Project SynthesisTable 6.1. Estimates of land in Chaco Canyon available for crop production.Investigator Criterion Acres HectaresHayes (1981) Canyon floor alluvium 3,200 1,295Loose and Lyons (1976a) Vegetative zones associated with old fields defmed by Potter and 3,584 1,451Kelley (1980)Gwinn Vivian (1974b, Area covered by floodwater from side canyons 2,667 1,0801991:66)If lower moisture levels charted by Windes(1987[I]:Figures 2.2 and 2.3) prompted farmers toconstruct Bc 362 around A.D. 1088 on an alluvial fanat the bottom of a major side drainage during a periodof stress (ca. A.D. 1081 to 1099), later expansion ofthe site in the early A.D. 1100s would have allowedthe inhabitants to take advantage of a longer andwetter period that followed. The demise of the site inthe early A.D. ll00s may correlate with the onset ofa long-term drought beginning around A.D. 1126.The late sherds obtained from the water control featureby Gwinn Vivian suggest that this system may havebeen reused by people living at another site in anattempt to alleviate effects of the A.D. 1130 to 1180drought.Dating of the water control system and associatedgardens is difficult to establish. Of the systemslocated on the north side of the canyon in the 15-kmstretch from Wijiji to the confluence of the Chaco andEscavada washes (Gwinn Vivian 1974b, 1984, 1990:309-313, 1991, 1992), we know the most about theChetro Ketl field (Loose and Lyons 1976a) that Vivianused to model the Rincon-4 system (Vivian 1974b,1992:51). Near Chetro Ketl, one of the gates that funneledwater through the gardens had been remodeled,reconstructed, or repaired at least once, probably dueto a flood that washed out the structure. Vivian(personal communication, 2002) thinks that this repairoccurred soon thereafter and is not representative ofdifferent periods of use. He reasoned that if the gridborders were being constructed in the early to mid­A.D. l100s using earlier refuse, the occasionalMcElmo sherd might represent refuse washing downfrom the pueblo. Vivian indicated that sherdsrecovered from this system span the period from A.D.1050 to 1200. The mid- to late-A.D. 1200s archaeomagneticdate obtained by Nichols (1975) anddiscussed by Loose and Lyons (1976a) might suggesteven later use of the fields than the Wingate Black-onredsherds indicate. At Casa Rinconada there issimilar evidence for one instance of change in the useof features. Here the latest canal orientation runsapproximately at a 45-degree angle from an earlier,deeper canal (personal communication, 2002). Vivianis currently preparing an in-depth report on hisresearch, which hopefully will help clarify the use ofthese features.In summary, the Chacoans used several differentfarming techniques, mainly along the canyon bottom.Table 6.1 summarizes estimations of possible cropproduction areas on the canyon floor. Hayes (1981)calculated the area of the canyon floor covered byalluvium. The range of numbers (from 1,080 to 1,451ha [2,667 to 3,584 aD probably encompass the actualarea under cultivation, yet not all of this area wasnecessarily in use contemporaneously. Schelberg(1982a: 116-118) introduced fallowing ofland into theevaluation of Chacoan agricultural practices. He suggesteddecreasing the available acreage by either 40 or50 percent to allow for renewal of soils. Is fallownecessary? Perhaps not; natural accumulation of newsoils probably occurred during certain periods. Judd(1964:224-225), Jackson (1878), and Bryan (1954) allindicated accumulation of from 1.2 to 4.8 m (4 to 16ft) of soil in the Chaco Wash between Pueblo I andPueblo III. The deposit of several feet of soils abovethe lower clay level where Pueblo I sherds wererecovered to the upper clay levels in the Chetro Ketlfields (Loose and Lyons 1976a) also indicated thatfallow may not have been necessary. Any discussionof agricultural practices, however, should not dismissthis consideration.