Hydrostratigraphic Model Development from Ground and Airborne Geophysical Surveys of the Western Hualapai Reservation near Grand Canyon West, Arizona, USA

Abstract:

In the desert southwestern United States, sustainable water resource planning is hindered in part by uncertainty in the geologic structure. On the western Hualapai Indian Reservation along the southern rim of the Grand Canyon, deep water tables and limited well infrastructure have led to subsurface geologic models that are well constrained at canyon outcrops, but poorly defined elsewhere, leading to structural uncertainty and hampering the development of realistic groundwater models. The U.S. Geological Survey has recently undertaken a series of geophysical surveys to supplement the notably spectacular outcrop observations of Truxton Basin and Hualapai Plateau, including audiomagnetotelluric profiles, gravity measurements, and a 1400-km airborne electromagnetic and magnetic survey. These data are being used to develop high-resolution maps of the hydrostratigraphy, including updated maps of regional aquifer contacts and the identification of geologic structures such as faults and buried paleocanyons. These geologic structures likely place significant controls on groundwater flow and may present preferential groundwater recharge pathways. These data also provide new constraint on the geometry of regional structures that are significant to the geologic evolution of the Grand Canyon region, including the southern terminus of the Hurricane fault, an active extensional fault along the margin between the Basin and Range and Colorado Plateau provinces.