Hydrogeologic Framework data and models for the Eel River groundwater basin, Humboldt County, California

This data release contains a geospatial database related to a digital 3D hydrogeologic framework model (3D HFM) of the Eel River Valley groundwater basin, California. The geospatial database contains two main data elements: (1) input data to the 3D HFM; (2) interpolated elevations and thicknesses of hydrogeologic units as a cellular array, which are a spatial representation of the 3D HFM results. Three hydrogeologic framework models of the same extent and similar conceptualization but successively increasing complexity were developed to characterize the structure, thickness, and extent of the materials within the basin; data from each phase of model-building are contained in this data release. The Phase 1 3D HFM has three hydrogeologic units (HGUs) and is based on a state-scale geologic map and generalized geologic cross sections, with no faults. The Phase 2 3D HFM has four HGUs and refines the elevation and thickness of the HGUs using data from detailed geologic maps and on structure contour and isopach maps that were based on formation tops picked from oil and gas well logs; the model includes faults. The Phase 3 3D HFM has seven HGUs and further refines the elevation and thickness of the HGUs using additional detailed geologic map data and stratigraphic interpretation of lithology data from water wells; the model includes faults. Each 3D HFM is a digital representation of the subsurface configuration of the HGUs that can be visualized in three dimensions and directly incorporated into numerical flow models. Input data to the 3D HFMs included in this data release include surface map data polygons of the hydrogeologic units, fault traces, and structure contour and isopach data that were used in the Phase 2 and 3 HFMs to define the extent and thickness of the deepest basin-filling hydrogeologic unit. Textural (grain size) data were compiled from driller’s lithologic logs from water wells. Well locations are included as point data within the geospatial database; the lithologic data from downhole intervals in each borehole are tabulated in spreadsheet form. The interpolated elevations and thickness of stratigraphic units are presented as a cellular array: essentially a “flattened”, two-dimensional representation of the digital 3D geologic framework, which defines the elevation and thickness of the HGUs within the 3D HFMs from each phase of model construction. The elevation and thickness of the geologic units are contained within a single polygon feature class ModelCells, which contains a mesh of polygons that represent model cells that have multiple attributes including XY location, elevation and thickness of each hydrogeologic unit. The spatial data are accompanied by non-spatial tables that describe the sources of geologic information, a glossary of terms, a description of model units, and a Data Dictionary that duplicates the Entity and Attribute information contained in the metadata file. Spatial data are also presented as shapefiles.