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Geoff Cromwell, PhD

(He/him)

Geoff Cromwell is a geologist at the California Water Science Center in Santa Maria, California

Dr. Cromwell's research explores hydrologic systems processes through the development of three-dimensional geologic and hydrogeologic framework models and integrating those models with groundwater, surface-water, and geophysical data. The scope of his work ranges from basin-scale to national-scale, from areas that are data-poor to areas that are data-rich, with a focus on understanding the geologic and hydrogeologic controls on hydrologic systems.

Professional Experience

  • Geologist at USGS California Water Science Center, Santa Maria, CA (2016 – Present)

  • Adjunct Assistant Professor in Geology at Occidental College, Los Angeles, CA (2014 – 2015)

  • Hydrologist at USGS California Water Science Center, San Diego, CA (2014 – 2015)

  • Hydrologic Technician–Student Trainee at USGS California Water Science Center, San Diego, CA (2011 – 2014)

Education and Certifications

  • Ph.D., Earth Sciences, Scripps Institution of Oceanography, University of California San Diego, 2014

  • M.S., Earth Sciences, Scripps Institution of Oceanography, University of California San Diego, 2010

  • B.A., Geology, Occidental College, 2008

Science and Products

link
aerial view of Paso Robles, CA

Evaluation of Groundwater Resources in the Adelaida Area of San Luis Obispo County, California

Stakeholders in San Luis Obispo County are concerned that the increased demand for water use has, and will continue to, affect groundwater levels and availability in the Adelaida area. To address stakeholder concerns, the County of San Luis Obispo Board of Supervisors has asked the USGS to conduct a comprehensive evaluation of groundwater resources of the Adelaida area.
By
California Water Science Center
link

Evaluation of Groundwater Resources in the Adelaida Area of San Luis Obispo County, California

Stakeholders in San Luis Obispo County are concerned that the increased demand for water use has, and will continue to, affect groundwater levels and availability in the Adelaida area. To address stakeholder concerns, the County of San Luis Obispo Board of Supervisors has asked the USGS to conduct a comprehensive evaluation of groundwater resources of the Adelaida area.
Learn More
link
San Antonio Creek Groundwater Basin

San Antonio Creek Water Availability

Located in Santa Barbara County, California, the San Antonio Creek Groundwater Basin is a rural agricultural area that is reliant on local water supplies, predominantly groundwater. Because of the growth of irrigated agriculture in the area, water demands have increased significantly, taxing local groundwater supplies. Groundwater resources are also used to supply local inhabitants, as well as...
By
California Water Science Center
link

San Antonio Creek Water Availability

Located in Santa Barbara County, California, the San Antonio Creek Groundwater Basin is a rural agricultural area that is reliant on local water supplies, predominantly groundwater. Because of the growth of irrigated agriculture in the area, water demands have increased significantly, taxing local groundwater supplies. Groundwater resources are also used to supply local inhabitants, as well as...
Learn More
link
location map of the Yucaipa area in Southern California. Faults in the area are also displayed.

Yucaipa Subbasin Integrated Hydrologic Model

The USGS is developing a hydrologic model of the Yucaipa Subbasin to aid in evaluating and managing the groundwater resources in the area. The study results will provide a greater understanding of the geohydrology of the subbasin, and aid in the development of a groundwater-monitoring plan, as well as in the evaluation of potential hydrologic effects of future groundwater development and...
By
California Water Science Center
link

Yucaipa Subbasin Integrated Hydrologic Model

The USGS is developing a hydrologic model of the Yucaipa Subbasin to aid in evaluating and managing the groundwater resources in the area. The study results will provide a greater understanding of the geohydrology of the subbasin, and aid in the development of a groundwater-monitoring plan, as well as in the evaluation of potential hydrologic effects of future groundwater development and...
Learn More

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.
By
California Water Science Center

Hydrogeologic data of the Russian River Watershed, Sonoma and Mendocino Counties, California (ver. 1.1, July 2023)

This data release contains digital data generated by the U.S. Geological Survey under cooperative agreements with Sonoma County Water Agency and the California State Water Resources Control Board to characterize the three-dimensional hydrogeology and water quality of the Russian River Watershed, located in the northern part of the California Coast Ranges section of the Pacific Border province. Thi
By
California Water Science Center

Hydrogeologic Data from the Cahuilla Valley and Terwilliger Valley Groundwater Basins, Riverside County, California, 2022

The U.S. Geological Survey (USGS) entered into a cooperative study with the California Department of Water Resources and the Ramona Band of Cahuilla to characterize the hydrogeology of the Cahuilla Valley and Terwilliger Valley groundwater basins and surrounding water-bearing units, with the ultimate goal of developing a calibrated integrated hydrologic model to manage the groundwater supplies on
By
California Water Science Center

Data release of hydrogeologic data of the Yucaipa groundwater subbasin, San Bernardino and Riverside Counties, California

This data release contains digital data generated by the U.S. Geological Survey under cooperative agreements with San Bernardino Valley Municipal Water District to characterize the three-dimensional hydrogeology of the Yucaipa groundwater subbasin, located east of Los Angeles in southern California. This dataset contains borehole lithologic data, and geospatial data of a three-dimensional hydrogeo
By
California Water Science Center

Data Release of hydrogeologic data from the San Antonio Creek Valley watershed, Santa Barbara County, California, 2015-2019

The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County about 15 miles (mi) south of Santa Maria, California and 55 mi north of Santa Barbara, California. The SACVW, is about 140 square miles and encompasses the San Antonio Creek Valley groundwater basin. Since the late 1800s, groundwater has been the primary source of water for agricultural, military, municipal,
By
National Cooperative Geologic Mapping Program, California Water Science Center

Select borehole data for Edwards Airforce Base and vicinity, Antelope Valley, CA

Edwards Air Force Base (EAFB) is located in Kern County, CA, approximately 35 kilometers (km) northeast of Lancaster and 9 km south of California City. The Air Force Research Laboratory (AFRL) is situated on EAFB, approximately 7 km southwest of Boron, CA. Release of contaminants from the AFRL facilities have contaminated local groundwater, which is mostly restricted to fractured granitic bedrock,
By
California Water Science Center

Yucaipa valley integrated hydrological model

IntroductionThe hydrologic system in the Yucaipa Valley watershed (YVW) was simulated using the coupled Groundwater and Surface-water FLOW model (GSFLOW; Markstrom and others, 2008). This study uses version 2.0 of GSFLOW, which is a combination of the Precipitation-Runoff Modeling System (PRMS; Markstrom and others, 2015), and the Newton-Raphson formulation of the Modular Groundwater-Flow Model (M
Authors
Ayman H. Alzraiee, John A. Engott, Geoffrey Cromwell, Linda R. Woolfenden
By
Water Resources Mission Area, California Water Science Center

Hydrogeologic characterization of the Yucaipa groundwater subbasin

IntroductionWater management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California (fig. A1) is complex with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yucai
Authors
Geoffrey Cromwell, John A. Engott, Ayman H. Alzraiee, Christina Stamos-Pfeiffer, Gregory Mendez, Meghan C. Dick, Sandra Bond
By
Water Resources Mission Area, California Water Science Center

Simulation of groundwater and surface-water resources of the San Antonio Creek Valley watershed, Santa Barbara County, California

In the San Antonio Creek Valley watershed (SACVW), western Santa Barbara County, California, groundwater is the primary source of water for agricultural irrigation, the town of Los Alamos, and supplemental water to Vandenberg Space Force Base (VSFB). Groundwater pumpage has increased since the 1970s as non-irrigated agricultural land has been converted to irrigated land and as local pumping for mu
Authors
Linda R. Woolfenden, John A. Engott, Joshua Larsen, Geoffrey Cromwell
By
Water Resources Mission Area, California Water Science Center

Hydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California

The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County, about 15 miles south of Santa Maria and 55 miles north of Santa Barbara, California. The SACVW is about 135 square miles and encompasses the San Antonio Creek Valley groundwater basin; the SACVW is separated from adjacent groundwater basins by the Casmalia and Solomon Hills to the north, and the Purisima Hil
Authors
Geoffrey Cromwell, Donald S. Sweetkind, Jill N. Densmore, John A. Engott, Whitney A. Seymour, Joshua Larsen, Christopher P. Ely, Christina L. Stamos, Claudia C. Faunt
By
Water Resources Mission Area, National Cooperative Geologic Mapping Program, California Water Science Center

Hydrology of the Yucaipa groundwater subbasin: Characterization and integrated numerical model, San Bernardino and Riverside Counties, California

Executive SummaryWater management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California is a complex task with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yuc
By
Water Resources Mission Area, California Water Science Center

Geology and hydrogeology of the Yucaipa groundwater subbasin, San Bernardino and Riverside Counties, California

The Yucaipa groundwater subbasin (referred to in this report as the Yucaipa subbasin) is located about 75 miles (mi) east of of Los Angeles and about 12 mi southeast of the City of San Bernardino. In the Yucaipa subbasin, as in much of southern California, limited annual rainfall and large water demands can strain existing water supplies; therefore, understanding local surface water and groundwate
Authors
Geoffrey Cromwell, Jonathan C. Matti
By
Water Resources Mission Area, California Water Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Depth to bedrock based on modeling of gravity data of the eastern part of Edwards Air Force Base, California

We describe a gravity survey acquired to determine the thickness of basin-fill deposits (depth to bedrock) and to delineate geologic structures that might influence groundwater flow beneath the eastern part of Edwards Air Force Base, California. Inversion of these gravity data combined with geologic map and well information provides an estimate of the thickness of basin-fill deposits (defined here
Authors
Victoria Langenheim, Andrew Morita, Allen H. Christensen, Geoffrey Cromwell, Christopher P. Ely
By
National Cooperative Geologic Mapping Program, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center

Using a GIS to populate 3D geocellular geologic models

No abstract available
Authors
Donald S. Sweetkind, Geoffrey Cromwell
By
Water Resources Mission Area, Geosciences and Environmental Change Science Center, California Water Science Center

Holocene paleointensity of the Island of Hawai'i from glassy volcanics

This study presents new high‐quality paleointensity records and 14C radiocarbon age determinations from the Island of Hawai `i during the Holocene. Previous studies on Hawai `i use experimental methods and statistical selection criteria that may produce inaccurate geomagnetic field strength estimates. Additional high‐quality paleointensity results can be used to evaluate the existing Hawaiian data
Authors
Geoffrey Cromwell, Frank A. Trusdell, Lisa Tauxe, Hubert Staudigel, Hagai Ron
By
Water Resources Mission Area, California Water Science Center

Santa Barbara and Foothill groundwater basins Geohydrology and optimal water resources management—Developed using density dependent solute transport and optimization models

Groundwater has been a part of the city of Santa Barbara’s water-supply portfolio since the 1800s; however, since the 1960s, the majority of the city’s water has come from local surface water, and the remainder has come from groundwater, State Water Project, recycled water, increased water conservation, and as needed, seawater desalination. Although groundwater from the Santa Barbara and Foothill
Authors
Scott R. Paulinski, Tracy Nishikawa, Geoffrey Cromwell, Scott E. Boyce, Zachary P. Stanko
By
Water Resources Mission Area, California Water Science Center

Against the current— The Mojave River from sink to source: The 2018 Desert Symposium field trip road log

The Mojave River evolved over the past few million years by “fill and spill” from upper basins near its source in the Transverse Ranges to lower basins. Each newly “spilled into” basin in the series? sustained a long-lived lake but gradually filled with Mojave River sediment, leading to spill to a yet lower elevation? basin. The Mojave River currently terminates at Silver Lake, near Baker, CA, but
Authors
David M. Miller, R.E. Reynolds, Krishangi D. Groover, David C. Buesch, H. J. Brown, Geoffrey Cromwell, Jill N. Densmore, A.L. Garcia, D. Hughson, J.R. Knott, Jeffrey E. Lovich
By
Energy and Minerals Mission Area, Energy Resources Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Minerals, Energy, and Geophysics Science Center

Water-resources and land-surface deformation evaluation studies at Fort Irwin National Training Center, Mojave Desert, California

The U.S. Army Fort Irwin National Training Center (NTC), in the Mojave Desert, obtains all of its potable water supply from three groundwater basins (Irwin, Langford, and Bicycle) within the NTC boundaries (fig. 1; California Department of Water Resources, 2003). Because of increasing water demands at the NTC, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, completed several
Authors
Jill N. Densmore, Justine E. Dishart, David M. Miller, David C. Buesch, Lyndsay B. Ball, Paul A. Bedrosian, Linda R. Woolfenden, Geoffrey Cromwell, Matthew K. Burgess, Joseph Nawikas, David O'Leary, Adam Kjos, Michelle Sneed, Justin T. Brandt
By
Water Resources Mission Area, California Water Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Non-USGS Publications**

Cromwell, G., Tauxe, L., Staudigel, H., Constable, C.G., Koppers, A.A.P., Pedersen, R.-B., 2013, In search of long-term hemispheric asymmetry in the geomagnetic field: Results from high northern latitudes, Geochemistry Geophysics Geosystems, 14, 8, (3234-3249), https://doi.org/10.1002/ggge.20174. Non-USGS Affiliation.
Cromwell, G., Constable, C.G., Staudigel, H., Tauxe, L., Gans, P., 2013, Revised and updated paleomagnetic results from Costa Rica, Geochemistry Geophysics Geosystems, 14, 9, (3379-3388), https://doi.org/10.1002/ggge.20199. Non-USGS Affiliation.
Cromwell, G., Tauxe, L., Staudigel, H., Ron, H., 2015, Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material, Physics of the Earth and Planetary Interiors, 241, (44-56), https://doi.org/10.1016/j.pepi.2014.12.007. Non-USGS Affiliation.
Cromwell, G., Tauxe, L., Halldórsson, S.A., 2015, New paleointensity results from rapidly cooled Icelandic lavas: Implications for Arctic geomagnetic field strength, Journal of Geophysical Research, Solid Earth, 120, 5, (2913-2934), https://doi.org/10.1002/2014JB011828. Non-USGS Affiliation.
Cai, S., Tauxe, L., and Cromwell, G., 2017, Paleointensity from subaerial basaltic glasses from the Second Hawaii Scientific Drilling Project (HSDP2) core and implications for possible bias in data from lava flow interiors: Journal of Geophysical Research: Solid Earth, 122, https://doi.org/10.1002/2017JB014683. Non-USGS Affiliation.
Cromwell, G., Johnson, C.L., Tauxe, L., Constable, C.G., and Jarboe, N.A, 2018, PSV10: A Global Data Set for 0–10 Ma time‐averaged field and paleosecular variation studies, Geochemistry Geophysics Geosystems, 19, 5, (1533-1558), https://doi.org/10.1002/2017GC007318. Non-USGS Affiliation, [C:60, D:90, I:70, W:80].
Miles, N.D., Deustua, S.E., Tancredi, G., Schnyder, G., Nesmachnow, S., and Cromwell, G., 2021, Using cosmic rays detected by HST as geophysical markers. I. Detection and characterization of cosmic rays: The Astrophysical Journal, 916 (86), 28 p., https://doi.org/10.3847/1538-4357/abfa9b. Non-USGS Affiliation, [C:10, D:10, I:10, W:10].
Cromwell, G., and Zhang, Y., 2021, New paleointensity data from Aniakchak volcano, Alaska, USA; Geochemistry Geophysics Geosystems, 22, e2021GC010032. https://doi.org/10.1029/2021GC010032. Non-USGS Affiliation, [C:100, D:60, I:70, W:70].
Cych, B., Tauxe, L., Cromwell, G., Sinton, J., and Koppers, A.A.P., 2023, Changes in non-dipolar field structure over the Plio-Pleistocene: New paleointensity results from Hawai`i compared to global data sets: Journal of Geophysical Research—Solid Earth, 128, 6, https://doi.org/10.1029/2023JB026492. Non-USGS Affiliation.

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

The Ups and Downs of Groundwater Levels after the July 2019 Ridgecrest, CA Earthquakes

The Ups and Downs of Groundwater Levels after the July 2019 Ridgecrest, CA Earthquakes

Effects from the two July 2019 Ridgecrest, CA earthquakes were observed in several USGS continuous groundwater-level monitoring sites in California...

Read Article

Science and Products

link
aerial view of Paso Robles, CA

Evaluation of Groundwater Resources in the Adelaida Area of San Luis Obispo County, California

Stakeholders in San Luis Obispo County are concerned that the increased demand for water use has, and will continue to, affect groundwater levels and availability in the Adelaida area. To address stakeholder concerns, the County of San Luis Obispo Board of Supervisors has asked the USGS to conduct a comprehensive evaluation of groundwater resources of the Adelaida area.
By
California Water Science Center
link

Evaluation of Groundwater Resources in the Adelaida Area of San Luis Obispo County, California

Stakeholders in San Luis Obispo County are concerned that the increased demand for water use has, and will continue to, affect groundwater levels and availability in the Adelaida area. To address stakeholder concerns, the County of San Luis Obispo Board of Supervisors has asked the USGS to conduct a comprehensive evaluation of groundwater resources of the Adelaida area.
Learn More
link
San Antonio Creek Groundwater Basin

San Antonio Creek Water Availability

Located in Santa Barbara County, California, the San Antonio Creek Groundwater Basin is a rural agricultural area that is reliant on local water supplies, predominantly groundwater. Because of the growth of irrigated agriculture in the area, water demands have increased significantly, taxing local groundwater supplies. Groundwater resources are also used to supply local inhabitants, as well as...
By
California Water Science Center
link

San Antonio Creek Water Availability

Located in Santa Barbara County, California, the San Antonio Creek Groundwater Basin is a rural agricultural area that is reliant on local water supplies, predominantly groundwater. Because of the growth of irrigated agriculture in the area, water demands have increased significantly, taxing local groundwater supplies. Groundwater resources are also used to supply local inhabitants, as well as...
Learn More
link
location map of the Yucaipa area in Southern California. Faults in the area are also displayed.

Yucaipa Subbasin Integrated Hydrologic Model

The USGS is developing a hydrologic model of the Yucaipa Subbasin to aid in evaluating and managing the groundwater resources in the area. The study results will provide a greater understanding of the geohydrology of the subbasin, and aid in the development of a groundwater-monitoring plan, as well as in the evaluation of potential hydrologic effects of future groundwater development and...
By
California Water Science Center
link

Yucaipa Subbasin Integrated Hydrologic Model

The USGS is developing a hydrologic model of the Yucaipa Subbasin to aid in evaluating and managing the groundwater resources in the area. The study results will provide a greater understanding of the geohydrology of the subbasin, and aid in the development of a groundwater-monitoring plan, as well as in the evaluation of potential hydrologic effects of future groundwater development and...
Learn More

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.
By
California Water Science Center

Hydrogeologic data of the Russian River Watershed, Sonoma and Mendocino Counties, California (ver. 1.1, July 2023)

This data release contains digital data generated by the U.S. Geological Survey under cooperative agreements with Sonoma County Water Agency and the California State Water Resources Control Board to characterize the three-dimensional hydrogeology and water quality of the Russian River Watershed, located in the northern part of the California Coast Ranges section of the Pacific Border province. Thi
By
California Water Science Center

Hydrogeologic Data from the Cahuilla Valley and Terwilliger Valley Groundwater Basins, Riverside County, California, 2022

The U.S. Geological Survey (USGS) entered into a cooperative study with the California Department of Water Resources and the Ramona Band of Cahuilla to characterize the hydrogeology of the Cahuilla Valley and Terwilliger Valley groundwater basins and surrounding water-bearing units, with the ultimate goal of developing a calibrated integrated hydrologic model to manage the groundwater supplies on
By
California Water Science Center

Data release of hydrogeologic data of the Yucaipa groundwater subbasin, San Bernardino and Riverside Counties, California

This data release contains digital data generated by the U.S. Geological Survey under cooperative agreements with San Bernardino Valley Municipal Water District to characterize the three-dimensional hydrogeology of the Yucaipa groundwater subbasin, located east of Los Angeles in southern California. This dataset contains borehole lithologic data, and geospatial data of a three-dimensional hydrogeo
By
California Water Science Center

Data Release of hydrogeologic data from the San Antonio Creek Valley watershed, Santa Barbara County, California, 2015-2019

The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County about 15 miles (mi) south of Santa Maria, California and 55 mi north of Santa Barbara, California. The SACVW, is about 140 square miles and encompasses the San Antonio Creek Valley groundwater basin. Since the late 1800s, groundwater has been the primary source of water for agricultural, military, municipal,
By
National Cooperative Geologic Mapping Program, California Water Science Center

Select borehole data for Edwards Airforce Base and vicinity, Antelope Valley, CA

Edwards Air Force Base (EAFB) is located in Kern County, CA, approximately 35 kilometers (km) northeast of Lancaster and 9 km south of California City. The Air Force Research Laboratory (AFRL) is situated on EAFB, approximately 7 km southwest of Boron, CA. Release of contaminants from the AFRL facilities have contaminated local groundwater, which is mostly restricted to fractured granitic bedrock,
By
California Water Science Center

Yucaipa valley integrated hydrological model

IntroductionThe hydrologic system in the Yucaipa Valley watershed (YVW) was simulated using the coupled Groundwater and Surface-water FLOW model (GSFLOW; Markstrom and others, 2008). This study uses version 2.0 of GSFLOW, which is a combination of the Precipitation-Runoff Modeling System (PRMS; Markstrom and others, 2015), and the Newton-Raphson formulation of the Modular Groundwater-Flow Model (M
Authors
Ayman H. Alzraiee, John A. Engott, Geoffrey Cromwell, Linda R. Woolfenden
By
Water Resources Mission Area, California Water Science Center

Hydrogeologic characterization of the Yucaipa groundwater subbasin

IntroductionWater management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California (fig. A1) is complex with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yucai
Authors
Geoffrey Cromwell, John A. Engott, Ayman H. Alzraiee, Christina Stamos-Pfeiffer, Gregory Mendez, Meghan C. Dick, Sandra Bond
By
Water Resources Mission Area, California Water Science Center

Simulation of groundwater and surface-water resources of the San Antonio Creek Valley watershed, Santa Barbara County, California

In the San Antonio Creek Valley watershed (SACVW), western Santa Barbara County, California, groundwater is the primary source of water for agricultural irrigation, the town of Los Alamos, and supplemental water to Vandenberg Space Force Base (VSFB). Groundwater pumpage has increased since the 1970s as non-irrigated agricultural land has been converted to irrigated land and as local pumping for mu
Authors
Linda R. Woolfenden, John A. Engott, Joshua Larsen, Geoffrey Cromwell
By
Water Resources Mission Area, California Water Science Center

Hydrogeologic characterization of the San Antonio Creek Valley watershed, Santa Barbara County, California

The San Antonio Creek Valley watershed (SACVW) is located in western Santa Barbara County, about 15 miles south of Santa Maria and 55 miles north of Santa Barbara, California. The SACVW is about 135 square miles and encompasses the San Antonio Creek Valley groundwater basin; the SACVW is separated from adjacent groundwater basins by the Casmalia and Solomon Hills to the north, and the Purisima Hil
Authors
Geoffrey Cromwell, Donald S. Sweetkind, Jill N. Densmore, John A. Engott, Whitney A. Seymour, Joshua Larsen, Christopher P. Ely, Christina L. Stamos, Claudia C. Faunt
By
Water Resources Mission Area, National Cooperative Geologic Mapping Program, California Water Science Center

Hydrology of the Yucaipa groundwater subbasin: Characterization and integrated numerical model, San Bernardino and Riverside Counties, California

Executive SummaryWater management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California is a complex task with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yuc
By
Water Resources Mission Area, California Water Science Center

Geology and hydrogeology of the Yucaipa groundwater subbasin, San Bernardino and Riverside Counties, California

The Yucaipa groundwater subbasin (referred to in this report as the Yucaipa subbasin) is located about 75 miles (mi) east of of Los Angeles and about 12 mi southeast of the City of San Bernardino. In the Yucaipa subbasin, as in much of southern California, limited annual rainfall and large water demands can strain existing water supplies; therefore, understanding local surface water and groundwate
Authors
Geoffrey Cromwell, Jonathan C. Matti
By
Water Resources Mission Area, California Water Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Depth to bedrock based on modeling of gravity data of the eastern part of Edwards Air Force Base, California

We describe a gravity survey acquired to determine the thickness of basin-fill deposits (depth to bedrock) and to delineate geologic structures that might influence groundwater flow beneath the eastern part of Edwards Air Force Base, California. Inversion of these gravity data combined with geologic map and well information provides an estimate of the thickness of basin-fill deposits (defined here
Authors
Victoria Langenheim, Andrew Morita, Allen H. Christensen, Geoffrey Cromwell, Christopher P. Ely
By
National Cooperative Geologic Mapping Program, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center

Using a GIS to populate 3D geocellular geologic models

No abstract available
Authors
Donald S. Sweetkind, Geoffrey Cromwell
By
Water Resources Mission Area, Geosciences and Environmental Change Science Center, California Water Science Center

Holocene paleointensity of the Island of Hawai'i from glassy volcanics

This study presents new high‐quality paleointensity records and 14C radiocarbon age determinations from the Island of Hawai `i during the Holocene. Previous studies on Hawai `i use experimental methods and statistical selection criteria that may produce inaccurate geomagnetic field strength estimates. Additional high‐quality paleointensity results can be used to evaluate the existing Hawaiian data
Authors
Geoffrey Cromwell, Frank A. Trusdell, Lisa Tauxe, Hubert Staudigel, Hagai Ron
By
Water Resources Mission Area, California Water Science Center

Santa Barbara and Foothill groundwater basins Geohydrology and optimal water resources management—Developed using density dependent solute transport and optimization models

Groundwater has been a part of the city of Santa Barbara’s water-supply portfolio since the 1800s; however, since the 1960s, the majority of the city’s water has come from local surface water, and the remainder has come from groundwater, State Water Project, recycled water, increased water conservation, and as needed, seawater desalination. Although groundwater from the Santa Barbara and Foothill
Authors
Scott R. Paulinski, Tracy Nishikawa, Geoffrey Cromwell, Scott E. Boyce, Zachary P. Stanko
By
Water Resources Mission Area, California Water Science Center

Against the current— The Mojave River from sink to source: The 2018 Desert Symposium field trip road log

The Mojave River evolved over the past few million years by “fill and spill” from upper basins near its source in the Transverse Ranges to lower basins. Each newly “spilled into” basin in the series? sustained a long-lived lake but gradually filled with Mojave River sediment, leading to spill to a yet lower elevation? basin. The Mojave River currently terminates at Silver Lake, near Baker, CA, but
Authors
David M. Miller, R.E. Reynolds, Krishangi D. Groover, David C. Buesch, H. J. Brown, Geoffrey Cromwell, Jill N. Densmore, A.L. Garcia, D. Hughson, J.R. Knott, Jeffrey E. Lovich
By
Energy and Minerals Mission Area, Energy Resources Program, Mineral Resources Program, National Laboratories Program, Science and Decisions Center, Geology, Minerals, Energy, and Geophysics Science Center

Water-resources and land-surface deformation evaluation studies at Fort Irwin National Training Center, Mojave Desert, California

The U.S. Army Fort Irwin National Training Center (NTC), in the Mojave Desert, obtains all of its potable water supply from three groundwater basins (Irwin, Langford, and Bicycle) within the NTC boundaries (fig. 1; California Department of Water Resources, 2003). Because of increasing water demands at the NTC, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, completed several
Authors
Jill N. Densmore, Justine E. Dishart, David M. Miller, David C. Buesch, Lyndsay B. Ball, Paul A. Bedrosian, Linda R. Woolfenden, Geoffrey Cromwell, Matthew K. Burgess, Joseph Nawikas, David O'Leary, Adam Kjos, Michelle Sneed, Justin T. Brandt
By
Water Resources Mission Area, California Water Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Non-USGS Publications**

Cromwell, G., Tauxe, L., Staudigel, H., Constable, C.G., Koppers, A.A.P., Pedersen, R.-B., 2013, In search of long-term hemispheric asymmetry in the geomagnetic field: Results from high northern latitudes, Geochemistry Geophysics Geosystems, 14, 8, (3234-3249), https://doi.org/10.1002/ggge.20174. Non-USGS Affiliation.
Cromwell, G., Constable, C.G., Staudigel, H., Tauxe, L., Gans, P., 2013, Revised and updated paleomagnetic results from Costa Rica, Geochemistry Geophysics Geosystems, 14, 9, (3379-3388), https://doi.org/10.1002/ggge.20199. Non-USGS Affiliation.
Cromwell, G., Tauxe, L., Staudigel, H., Ron, H., 2015, Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material, Physics of the Earth and Planetary Interiors, 241, (44-56), https://doi.org/10.1016/j.pepi.2014.12.007. Non-USGS Affiliation.
Cromwell, G., Tauxe, L., Halldórsson, S.A., 2015, New paleointensity results from rapidly cooled Icelandic lavas: Implications for Arctic geomagnetic field strength, Journal of Geophysical Research, Solid Earth, 120, 5, (2913-2934), https://doi.org/10.1002/2014JB011828. Non-USGS Affiliation.
Cai, S., Tauxe, L., and Cromwell, G., 2017, Paleointensity from subaerial basaltic glasses from the Second Hawaii Scientific Drilling Project (HSDP2) core and implications for possible bias in data from lava flow interiors: Journal of Geophysical Research: Solid Earth, 122, https://doi.org/10.1002/2017JB014683. Non-USGS Affiliation.
Cromwell, G., Johnson, C.L., Tauxe, L., Constable, C.G., and Jarboe, N.A, 2018, PSV10: A Global Data Set for 0–10 Ma time‐averaged field and paleosecular variation studies, Geochemistry Geophysics Geosystems, 19, 5, (1533-1558), https://doi.org/10.1002/2017GC007318. Non-USGS Affiliation, [C:60, D:90, I:70, W:80].
Miles, N.D., Deustua, S.E., Tancredi, G., Schnyder, G., Nesmachnow, S., and Cromwell, G., 2021, Using cosmic rays detected by HST as geophysical markers. I. Detection and characterization of cosmic rays: The Astrophysical Journal, 916 (86), 28 p., https://doi.org/10.3847/1538-4357/abfa9b. Non-USGS Affiliation, [C:10, D:10, I:10, W:10].
Cromwell, G., and Zhang, Y., 2021, New paleointensity data from Aniakchak volcano, Alaska, USA; Geochemistry Geophysics Geosystems, 22, e2021GC010032. https://doi.org/10.1029/2021GC010032. Non-USGS Affiliation, [C:100, D:60, I:70, W:70].
Cych, B., Tauxe, L., Cromwell, G., Sinton, J., and Koppers, A.A.P., 2023, Changes in non-dipolar field structure over the Plio-Pleistocene: New paleointensity results from Hawai`i compared to global data sets: Journal of Geophysical Research—Solid Earth, 128, 6, https://doi.org/10.1029/2023JB026492. Non-USGS Affiliation.

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

The Ups and Downs of Groundwater Levels after the July 2019 Ridgecrest, CA Earthquakes

The Ups and Downs of Groundwater Levels after the July 2019 Ridgecrest, CA Earthquakes

Effects from the two July 2019 Ridgecrest, CA earthquakes were observed in several USGS continuous groundwater-level monitoring sites in California...

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