Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA

Abstract Hydrogeologic systems in the southern Cascade Range California (USA) develop volcanic rocks where morphology, stratigraphy, extensional structures, and attendant basin geometry play a central role groundwater flow paths, groundwater/surface-water interactions, spring discharge locations. High-volume springs (greater than 3 m /s) from basin-filling (<800 ka) Hat Creek Fall River tributaries contribute approximately half of average annual Pit River, largest tributary to Shasta Lake. A hydrogeologic conceptual framework is constructed for combining new geologic mapping, water-well lithologic logs, database active faults, LiDAR mapping faults landforms, streamflow measurements airborne thermal infrared remote sensing stream temperature. These data are used integrate structure volcaniclastic stratigraphy create three-dimensional interpretation hydrogeology basin. Two large gains focused near Big Spring north Sugarloaf Peak result barriers that restrict lateral force water into Creek. The inferred groundwater-flow divide aquifer system at least three leaky compartments. two downstream compartments lose upstream reaches (immediately barriers) gain with greatest inflows immediately barriers.