DROUGHT EFFECTS ON PREHISTORIC SETTLEMENTS: PALEOHYDROLOGIC MODELING OF SPRING DISCHARGE, CANYON OF THE ANCIENTS NATIONAL MONUMENT, SOUTHWEST COLORADO

This unique study attempts to model the paleohydrology, viability of spring discharge and related climatic variations, with respect to prehistoric settlements in the Canyon of the Ancients National Monument, Colorado. Specifically, the intent is to understand and model the lagged response of ground-water resources in the study area to changes in precipitation and the broad impact of those changes on human occupation of the area. This is accomplished by understanding and modeling, for the first time, both the modern hydrologic and paleohydrologic systems of the coupled human/natural landscapes from A.D. 600 through 1300.

Multiple-scale, multi-temporal mathematical models simulating the relationships between environmental variables such as the frequency variations in precipitation, hydrogeology, and ground-water systems are used to predict paleohydrologic spring discharge. Prediction of the paleohydrologic spring discharge rates are then related to a direct response in prehistoric human settlement patterns as influenced by the viability of drinking water supplies over long periods of time.

Results show that although climate driven, the amount of drinking water available at any given time period corresponds proportionately to the effective extent of the Dakota/Burro Canyon aquifer recharge area. The resulting, delayed ground-water flow response is the direct function of the hydrogeologic characteristics of the aquifer being used by the prehistoric settlements. In most spring locations, some spring flow existed throughout both wet periods and times of drought, therefore, suggesting that other variables such as increasing population pressures were also important in the depopulation of the CANM region.