Electrical Resistivity Tomography Data at Fort Irwin National Training Center, San Bernardino County, California, 2015 and 2017

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.