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.

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.

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased groundwater pumping, recovery of water levels, and a reduced rate of compaction in some areas of the San Joaquin Valley. However, drought conditions during 1976–77, 1987–92, and drought conditions and operational reductions in surface-water deliveries during 2007–10 decreased surface-water availability, causing pumping to increase, water levels to decline, and renewed compaction. The U.S. Geological Survey, in cooperation with the California Department of Water Resources, assessed more recent land subsidence near a 145-kilometer reach of the California Aqueduct in the west-central part of the San Joaquin Valley using Interferometric Synthetic Aperture Radar (InSAR) methods. Analysis presented in Sneed and others (2018) is based, in part, on subsidence contours derived from InSAR data for January 2008–January 2010, and are presented in this data release.

Extensive groundwater withdrawal from the unconsolidated deposits in the San Joaquin Valley caused widespread aquifer-system compaction and resultant land subsidence from 1926 to 1970—locally exceeding 8.5 meters. The importation of surface water beginning in the early 1950s through the Delta-Mendota Canal and in the early 1970s through the California Aqueduct resulted in decreased groundwater pumping, recovery of water levels, and a reduced rate of compaction in some areas of the San Joaquin Valley. However, drought conditions during 1976–77, 1987–92, and drought conditions and operational reductions in surface-water deliveries during 2007–10 decreased surface-water availability, causing pumping to increase, water levels to decline, and renewed compaction. The U.S. Geological Survey, in cooperation with the California Department of Water Resources, assessed more recent land subsidence near a 145-kilometer reach of the California Aqueduct in the west-central part of the San Joaquin Valley using Interferometric Synthetic Aperture Radar (InSAR) methods. Analysis presented in Sneed and others (2018) is based, in part, on subsidence contours derived from InSAR data for January 2008–January 2010, and are presented in this data release.

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.

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.

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.