HYDROGEOLOGIC FRAMEWORK AND ESTIMATES OF GROUNDWATER STORAGE FOR THE HUALAPAI, DETRITAL, AND SACRAMENTO VALLEYS, ARIZONA

Alluvial aquifers in Hualapai, Detrital, and Sacramento Valley’s in northwest Arizona supply water exclusively from groundwater. Mohave County and the Arizona Department of Water Resources are concerned about potential changes in stored groundwater from increased water use for alternative energy in the newly proposed solar corridor and population growth. This study developed a conceptual hydrogeologic framework model (HFM) and estimates of groundwater storage describing the hydrostratigraphy and aquifer properties to guide the construction of a numerical water management tool for investigating long-term effects of increased water use.

The HFM and storage estimates based on new and existing hydrologic, geophysical, and geologic data, include gravity measurements, airborne transient electromagnetic (GEOTEM) profiles, ground-based transient electromagnetic measurements (TEM), and lithology from driller’s logs. GEOTEM resistivity profiles, surface geology, well log lithology, and water-levels guided the selection of hydrogeologic units (HGUs) within the alluvial aquifer and the contact with the bedrock. Lithology was inferred from TEM in areas were other data were unavailable. Saturated basin-fill sediment was simplified into two HGUs, saturated fine-grained basin-fill and saturated coarse-grained basin-fill.

Well logs provided better control then gravity data in areas of volcanic rock and where it was difficult to distinguish fine grained units and saline water along GEOTEM profiles. GEOTEM allowed for inferred distribution of coarse and fine grained HGUs. HGUs in Hualapai and Sacramento Valley’s contained distributions of coarse- and fine-grained sediments, however, Detrital Valley contained mostly fine-grained sediment. Initial results indicate Hualapai Valley includes the southern Gregg, Hualapai, and Kingman sub-basins with an estimated aquifer storage of 14.75 million ac-ft using a specific yield of 15 percent; Detrital Valley includes the northern Detrital, central Detrital, and southern Detrital sub-basins with an estimated aquifer storage of 6.8 million ac-ft using a specific yield of 8 percent; and Sacramento Valley includes the Chloride, Golden Valley, and Dutch Flat sub-basins with an estimated aquifer storage of 16 million ac-ft using a specific yield of 15 percent.