Synthetic aperture radar (SAR) data from the European Space Agency's (ESA) Sentinel-1A satellite were acquired for this study from the Alaska Satellite Facility (ASF) and used to generate spatially detailed land-surface deformation maps (interferograms) for the Mojave River and Morongo groundwater basins during 2014–19 using conventional InSAR methods.

Synthetic aperture radar (SAR) data from the European Space Agency's (ESA) Sentinel-1A satellite were acquired from the Alaska Satellite Facility and used to generate spatially detailed land-surface deformation maps (interferograms) for the Pajaro Valley during 2015 through 2018 using conventional Interferometric Synthetic Aperture Radar (InSAR) workflows. Groundwater level data collected by the Pajaro Valley Water Management Agency during 1970 to 2018 was provided to USGS and used to assess changes in groundwater levels as it relates to aquifer system compaction and resultant land subsidence in the Pajaro Valley.

Synthetic aperture radar (SAR) data from the European Space Agency's (ESA) Sentinel-1A satellite were acquired from the Alaska Satellite Facility and used to generate spatially detailed land-surface deformation maps (interferograms) for the Pajaro Valley during 2015 through 2018 using conventional Interferometric Synthetic Aperture Radar (InSAR) workflows. Groundwater level data collected by the Pajaro Valley Water Management Agency during 1970 to 2018 was provided to USGS and used to assess changes in groundwater levels as it relates to aquifer system compaction and resultant land subsidence in the Pajaro Valley.

Synthetic aperture radar (SAR) data from the European Space Agency's (ESA) Sentinel-1A satellite were acquired for this study from the Alaska Satellite Facility and used to generate spatially detailed land-surface deformation maps (interferograms) for the Pajaro Valley during 2015 through 2018 using conventional Interferometric Synthetic Aperture Radar (InSAR) workflows.

Synthetic aperture radar (SAR) data from the European Space Agency's (ESA) Sentinel-1A satellite were acquired for this study from the Alaska Satellite Facility and used to generate spatially detailed land-surface deformation maps (interferograms) for the Pajaro Valley during 2015 through 2018 using conventional Interferometric Synthetic Aperture Radar (InSAR) workflows.

The Central Valley, and particularly the San Joaquin Valley, has a long history of land subsidence caused by groundwater development. The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley lowered groundwater levels and caused widespread land subsidence—reaching 9 meters by 1981. More than half of the thickness of the aquifer system is composed of fine-grained sediments, including clays, silts, and sandy or silty clays that are susceptible to compaction. In an effort to aid water managers in understanding how water moves through the aquifer system, predicting water-supply scenarios, and addressing issues related to water competition, the United States Geological Survey (USGS) developed a new hydrologic modeling tool, the Central Valley Hydrologic Model (CVHM; Faunt and others 2009). For a more detailed description of satellite-based InSAR methods, please see Sneed and others (2013; 2018). For a more detailed description of UAVSAR, please see https://uavsar.jpl.nasa.gov/education/what-is-uavsar.html. The data presented in this data release was provided by Sneed and others (2013; 2018) and will be used to facilitate updates from CVHM to CVHM2 and represent subsidence observations (measurements) using satellite and airborne Interferometric Synthetic Aperture Radar (InSAR) data during 2003–2016. In the context of this report, subsidence is defined as the lowering of the land-surface elevation as a result of aquifer-system compaction and is calculated by differencing repeated elevation measurements. InSAR methods have been used to monitor land subsidence in the Central Valley and are discussed in more detail in the following sections.

The Central Valley, and particularly the San Joaquin Valley, has a long history of land subsidence caused by groundwater development. The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley lowered groundwater levels and caused widespread land subsidence—reaching 9 meters by 1981. More than half of the thickness of the aquifer system is composed of fine-grained sediments, including clays, silts, and sandy or silty clays that are susceptible to compaction. In an effort to aid water managers in understanding how water moves through the aquifer system, predicting water-supply scenarios, and addressing issues related to water competition, the United States Geological Survey (USGS) developed a new hydrologic modeling tool, the Central Valley Hydrologic Model (CVHM; Faunt and others 2009). For a more detailed description of satellite-based InSAR methods, please see Sneed and others (2013; 2018). For a more detailed description of UAVSAR, please see https://uavsar.jpl.nasa.gov/education/what-is-uavsar.html. The data presented in this data release was provided by Sneed and others (2013; 2018) and will be used to facilitate updates from CVHM to CVHM2 and represent subsidence observations (measurements) using satellite and airborne Interferometric Synthetic Aperture Radar (InSAR) data during 2003–2016. In the context of this report, subsidence is defined as the lowering of the land-surface elevation as a result of aquifer-system compaction and is calculated by differencing repeated elevation measurements. InSAR methods have been used to monitor land subsidence in the Central Valley and are discussed in more detail in the following sections.

During spring 2016, the U.S. Geological Survey and other agencies made approximately 1976 water-level measurements in the Mojave River and Morongo groundwater basins. A water-level contour map was drawn using a subset of data from about 645 wells, providing coverage for most of the basins. The contours represent the regional water table in spring 2016.

During spring 2016, the U.S. Geological Survey and other agencies made approximately 1976 water-level measurements in the Mojave River and Morongo groundwater basins. A water-level contour map was drawn using a subset of data from about 645 wells, providing coverage for most of the basins. The contours represent the regional water table in spring 2016.

The U.S. Geological Survey (USGS) collected gravity data in the eastern Mojave Desert, California and Nevada as an aid to characterizing the regional geologic framework. Gravity stations were located between approximately lat 35°10’ and 35°50’ N. and long 115°05’ and 115°50’ W. and were distributed from west to east across parts of Shadow Valley, Clark Mountain Range, Mescal Range, Ivanpah Valley, Lanfair Valley, Bobcat Hills, and New York Mountains. Gravity data were ultimately tied to a World Relative Gravity Reference Network of North America gravity base station at Nipton, California (Jablonski, 1974) and supersede previously published data (Denton and Ponce, 2018). In general, gravity anomalies can be used to infer the subsurface structure of geologic features, provided a physical-property contrast occurs across the geologic boundaries. Gravity anomalies can, for example, reveal variations in lithology and delineate features such as calderas, deep sedimentary basins, and faults, all of which play an important role in defining the geologic framework of a region (Ponce and Denton, 2018). Gravity data were processed using standard geophysical methods (for example; Blakely, 1995; Denton and Ponce, 2018). New gravity data are shown at the top of the data file and their reduction method matches previously published data. Gravity data include the following corrections: (1) earth-tide correction, which corrects for tidal attraction of the Moon and Sun; (2) instrument-drift correction, which compensates for drift in the instrument’s spring; (3) latitude correction, which accounts for variation in the Earth’s gravity with latitude; (4) free-air correction, which accounts for variation in gravity due to elevation relative to sea level; (5) Bouguer correction, which corrects for the attraction of material between the station and sea level; (6) curvature correction, which corrects the Bouguer correction for the effect of the Earth’s curvature; (7) terrain correction, which removes the effect of topography to a radial distance of 167 km from the station; and (8) isostatic correction, which removes long-wavelength variations in the gravity field related to the compensation of topographic loads. Denton, K.M., and Ponce, D.A., 2018, Gravity and magnetic studies of the eastern Mojave Desert, California and Nevada (rev. 1.1): U.S. Geological Survey Open-File Report 2016-1070, 20 p., https://doi.org/10.3133/ofr20161070. Jablonski, H.M., 1974, World relative gravity reference network North America, Parts 1 and 2, with a supplementary section on IGSN 71 gravity datum values (rev. ed.): U.S. Defense Mapping Agency Aerospace Center Reference Publication 25, 1261 p. Ponce, D.A., and Denton, K.M., 2018, Isostatic gravity map of Mountain Pass and vicinity, California and Nevada: U.S. Geological Survey Scientific Investigations Map 3412-A, 6 p., scale 1:62,500, https://doi.org/10.3133/sim3412A.