Doctor of Philosophy

dissertationWater is arguably the most important resource for successful crop production in the Southwest. In this dissertation, I examine the economic tradeoffs involved in dry farming maize vs. maize farming using simple surface irrigation for the Fremont farmers who occupied Range Creek Canyon, east-central Utah from AD 900 to 1200. To understand the costs and benefits of irrigation in the past, maize farming experiments are conducted. The experiments focus on the differences in edible grain yield as the amount of irrigation water is varied between farm plots. The temperature and precipitation were tracked along with the growth stages of the experimental crop. The weight of experimental harvest increased in each plot as the number of irrigations increased. The benefits of irrigation are clear, higher yields. The modern environmental constraints on farming in the canyon (precipitation, temperature, soils, and amount of arable land) were reconstructed to empirically scale variability in current maize farming productivity along the valley floor based on the results of the experimental crop. The results of farming productivity under modern environmental constraints are compared to the past using a tree-ring sequence to reconstruct water availability during the Fremont occupation of Range Creek Canyon. The reconstruction of past precipitation using tree ring data show that dry farming would have been extremely difficult during the period AD 900-1200 in Range Creek Canyon. Archaeological evidence indicates that the Fremont people were farming during this period suggesting irrigation was used to supplement precipitation shortfalls. Large amounts of contiguous arable land, highly suitable for irrigation farming, are identified along the valley bottom. The distribution of residential sites and associated surface rock alignment features are analyzed to determine whether the Fremont located themselves in close proximity to these areas identified as highly suitable for irrigation farming. Seventy-five percent of the residential sites in Range Creek Canyon are located near the five loci identified as highly suitable for irrigation farming