Fig 1.
General location of Chaco Canyon Cultural Historical Park in relation to the Chuska Mountains.
Four Corners is in upper left corner of figure at intersection of black state lines. Only selected major drainages contributing to or near Chaco Wash are represented. Black triangles are the three closest pedons to Chaco Canyon that have been sampled by the USDA.
Table 1.
Comparison of variations in electrical conductivity measurement.
Table 2.
Conversion equations for estimating measured electrical conductivity on a saturated extract.
Table 3.
This table shows estimated crop yield declines at particular soil or irrigation water conductivities.
ECe is a measurement on the extract from a saturated soil paste. ECw is the conductivity of irrigation water with yield declines based on an estimated 15–20% leaching fraction. These data are always presented as guidelines, not definitive limits, and are for modern crop varieties. Given the range of tolerance within a given crop type, see squashes, it is possible that varieties used by Chacoan farmers were less susceptible than modern varieties largely grown in wetter climates. Data, except for sunflower, is from [81]. Amaranthus, found to be part of diets at Salmon Ruin and Antelope House, is considered a tolerant plant to salinity [82]. Chenopodium, Amaranthus, and Asteraceae were found to be significant diet contributions [82], and each is considered a halophytic, or salt adapted, plant.
Fig 2.
Shows the relation of key water characteristics for 113 observations between 8/6/1976 and 10/6/1983.
The average for pH (7.55) and EC (0.46) are each indicated by a solid line behind each data type. Chaco discharge is shown for visual comparison of covariation between periods of increased flow and EC.
Fig 3.
Shows SAR variation from 41 measurements from 8/6/1976 to 10/6/1983.
Max SAR/fine—the highest flat horizontal line—is the maximum SAR value usable for irrigation on fine textured soils under any management practice and is the highest flat horizontal line. Mean SAR represents the value of 5.74. No SAR issues—the horizontal shaded area at the base—indicates that below a value of 3 there is no projected impact from the Na composition. The Na/SO4 Ratio is the simple ratio of the USGS data for each reported in mg/L. Shaded vertical bars indicate the seasonal period of precipitation at Chaco Canyon: July through October.
Fig 4.
Figure shows the location for all known soil salinity samples in the main are of Chaco Canyon.
Larger circles are to avoid providing precise location information for non-public archaeological areas. Selected profiles are presented with values for single depth samples shown next to their location. Blue circles, connected by a simple smoothed line for visual interpretation, represent estimated ECe values in profiles. For sources that specify a depth range for specific samples, point depth is the range midpoint. For each salinity graph, the Y-Axis is Depth (cm), and the X-Axis is Estimated ECe. Vertical lines represent varying yield decrease thresholds for maize (moving left to right): Yellow = 0%, Peach = 10%, Orange = 25%, Brown = 50%, and (when shown) Red = 100%. See S1 Table for raw and converted data.
Table 4.
Estimated time and labor efforts for Chuska residents to transport maize to Chaco Canyon based on varying population sizes, carrying capacities, and travel times.
Drennan [132] used loads of 20 and 50 kilograms in his studies of long distance transport. The final weight estimate derives from Malville [131], as reported in Windes and McKenna ([142] p136).
Table 5.
Estimated time and labor efforts for Chaco residents to transport maize to the canyon based on varying population sizes, carrying capacities, and travel times.
Round trip lengths are based on a distance of 85 km between Chaco Canyon and the Chuska Mountains. Six-day trips were suggested by Benson [33] based on traveling 26.67 km/day, while 9.5 and 27 days—assuming a speed of 18 km/day and 6.34 km/day respectively—were derived from travel times determined by Malville [137] and reported by Windes and McKenna ([142] p136). Drennan [132] used loads of 20 and 50 kilograms in his studies of long distance transport, both of which are paired with Benson’s assertion that the trip could be made in six days. The second two weight estimates derive from Malville [131], as reported in Windes and McKenna ([142] p136) and are directly linked to the trip lengths determined in the first column. Number of trips and travel days are rounded based on the completion of an entire trip.
Table 6.
Estimated transport time and labor efforts for transport of maize to the canyon by seasonal residents living 6 months in the Chuskas and 6 months in Chaco Canyon based on varying population sizes, carrying capacities, and travel times.
In this case, the amount of required maize is halved to represent only seasonal occupation within the canyon. Round trip lengths are based on a distance of 85 km between Chaco Canyon and the Chuska Mountains. Six-day trips were suggested by Benson [33] based on traveling 26.67 km/day, while 9.5 and 27 days—assuming a speed of 18 km/day and 6.34 km/day respectively—were derived from travel times determined by Malville [137] and reported by Windes and McKenna ([142] p136). Drennan [132] used loads of 20 and 50 kilograms in his studies of long distance transport, both of which are paired with Benson’s assertion that the trip could be made in six days. The second two weight estimates derive from Malville [131], as reported in Windes and McKenna ([142] p136) and are directly linked to the trip lengths determined in the first column. Number of trips and travel days are rounded based on the completion of an entire trip.