Human impact on natural systems modeled through soil erosion in GeoWEPP: A comparison between pre-Hispanic periods and modern times in the Teotihuacan Valley (Central Mexico)

Anthropogenic changes during the past 2000 years in the Teotihuacan Valley imply that intensity of soil degradation varies depending on the land management practices and the intensity of soil use. As a part of a broader effort to reconstruct erosion dynamics in the Teotihuacan Valley through geoarchaeological approaches, our study applies a process-based watershed hydrology and upland erosion model, the Water Erosion Prediction Project (WEPP). The Geo-spatial interface for WEPP (GeoWEPP) was used to characterize locations of soil detachment and sediment deposition predicted in the watershed through time, based on current and reconstructed conditions in the valley. Climate, topography, soil and land use were used as inputs to WEPP to estimate surface runoff and soil loss rates for periods with different environmental and anthropogenic conditions: the Teotihuacan period (1-650 CE), the Aztec period (1325-1521 CE) and for modern times (after 1970 CE). Over a simulated and established timeframe for those periods, surface runoff and rate of soil loss were estimated to be higher during the Aztec period, when the area devoted to agriculture dominated the landscape. Land use change had a major impact on soil erosion. Comparison of the pre-Hispanic periods with current conditions shows that WEPP is useful in showing the roles of management and climate in environmental degradation. The results contribute to the scientific debate about the antiquity and causes of erosion in central Mexico. The research shows that land use is one of the foremost factors affecting soil erosion, both in ancient and modern periods, with particular impact during the Aztec period.