Aquifer monitoring in the Big Chino Valley, Arizona
For this project gravity stations were collocated with monitoring wells to determine the storage/groundwater-level relation
Monitoring Minute 319 storage change
Gravity surveys were used to map infiltrated water during the Minute 319 “Pulse Flow” on the Colorado River
Mapping the Leupp, Arizona alluvial aquifer
Relative-gravity surveys were carried out to map the extent of the alluvial aquifer beneath the Little Colorado River
Tucson aquifer monitoring
The Southwest Gravity Program operates an A-10 absolute gravimeter, a rugged, field-portable instrument
The Southwest Gravity Program provides high-precision time-lapse gravity (repeat microgravity) data for hydrologic studies in the southwestern US. Recent projects include monitoring recharge underneath ephemeral-stream channels, monitoring aquifer-storage change in unconfined and compressible aquifers, measuring storage change at surface-spreading and injection-well artificial-recharge facilities, and estimating specific yield through the correlation of gravity and water-level change in wells. Projects range in scale from the site-specific (individual recharge basins) to regional (for example, the Tucson, Albuquerque, and Phoenix groundwater basins).
Gravity is affected by mass: the greater an object's mass, the stronger its gravitational pull. By measuring changes in gravity over time, inferences can be made about changes in mass. In hydrology, this can be used to study water in the subsurface. If the amount of groundwater in a particular area increases, through processes such as rainfall infiltration and aquifer recharge, gravity will also increase. Likewise, losses of groundwater storage, such as from pumping, discharge to streams, and evaporation, will cause gravity to decrease.
Data are usually collected in project-specific monitoring networks, using absolute gravity meters and relative gravity meters. Changes in gravity, measured as an acceleration (for example, m/s2), are readily converted to a thickness of free-standing water using the “Bouguer,” or infinite-slab, approximation. Data are published as Sciencebase Data Releases and in an online absolute-gravity database. Data releases are primarily network-adjusted (combined) relative- and absolute-gravity data.
The Southwest Gravity Program provides GSadjust software, for the network adjustment of relative- and absolute-gravity data. The software is designed to work with Scintrex and Burris relative-gravity data formats (also, free-format csv data can be entered) and Micro-g Lacoste absolute-gravity formats. GSadjust provides various drift correction options for relative-gravity data and can compute gravity change between surveys. GSadjust is optimized for data interaction, allowing the user to quickly see the effect of choices made during data processing (for example, choice of drift-correction method) on the adjusted gravity values. Also, an Excel Spreadsheet is available that calculates drift correction and gravity differences between stations.
Southwest Gravity Program Absolute-Gravity Database (updated 2022-07-08)
Procedures for field data collection, processing, quality assurance and quality control, and archiving of relative- and absolute-gravity surveys
Time-lapse gravity data for monitoring and modeling artificial recharge through a thick unsaturated zone
Groundwater response to the 2014 pulse flow in the Colorado River Delta
Gravity change from 2014 to 2015, Sierra Vista Subwatershed, Upper San Pedro Basin, Arizona
Hydrological conditions and evaluation of sustainable groundwater use in the Sierra Vista Subwatershed, Upper San Pedro Basin, southeastern Arizona
Accounting for time- and space-varying changes in the gravity field to improve the network adjustment of relative-gravity data
Initial characterization of the groundwater system near the Lower Colorado Water Supply Project, Imperial Valley, California
Surface and subsurface microgravity data in the vicinity of Sanford Underground Research Facility, Lead, South Dakota
Direct measurement of sub-surface mass change using the variable-baseline gravity gradient method
Results of the first North American comparison of absolute gravimeters, NACAG-2010
Gravity data from the San Pedro River Basin, Cochise County, Arizona
The utility of gravity and water-level monitoring at alluvial aquifer wells in southern Arizona
Use of Microgravity to Assess the Effects of El Nino on Ground-Water Storage in Southern Arizona
Changes in Gravity used to Quantify Groundwater-Storage Change in the Tucson AMA
The Tucson Active Management Area (AMA) is a semi-arid region in southern Arizona. Historically, groundwater pumping in the Tucson AMA exceeded recharge for many decades. Gravity-based methods developed by the USGS can be used to directly measure groundwater-storage changes, providing an estimate of total storage change that does not rely on uncertain estimates of inflows and outflows.
The Southwest Gravity Program provides high-precision time-lapse gravity (repeat microgravity) data for hydrologic studies in the southwestern US. Recent projects include monitoring recharge underneath ephemeral-stream channels, monitoring aquifer-storage change in unconfined and compressible aquifers, measuring storage change at surface-spreading and injection-well artificial-recharge facilities, and estimating specific yield through the correlation of gravity and water-level change in wells. Projects range in scale from the site-specific (individual recharge basins) to regional (for example, the Tucson, Albuquerque, and Phoenix groundwater basins).
Gravity is affected by mass: the greater an object's mass, the stronger its gravitational pull. By measuring changes in gravity over time, inferences can be made about changes in mass. In hydrology, this can be used to study water in the subsurface. If the amount of groundwater in a particular area increases, through processes such as rainfall infiltration and aquifer recharge, gravity will also increase. Likewise, losses of groundwater storage, such as from pumping, discharge to streams, and evaporation, will cause gravity to decrease.
Data are usually collected in project-specific monitoring networks, using absolute gravity meters and relative gravity meters. Changes in gravity, measured as an acceleration (for example, m/s2), are readily converted to a thickness of free-standing water using the “Bouguer,” or infinite-slab, approximation. Data are published as Sciencebase Data Releases and in an online absolute-gravity database. Data releases are primarily network-adjusted (combined) relative- and absolute-gravity data.
The Southwest Gravity Program provides GSadjust software, for the network adjustment of relative- and absolute-gravity data. The software is designed to work with Scintrex and Burris relative-gravity data formats (also, free-format csv data can be entered) and Micro-g Lacoste absolute-gravity formats. GSadjust provides various drift correction options for relative-gravity data and can compute gravity change between surveys. GSadjust is optimized for data interaction, allowing the user to quickly see the effect of choices made during data processing (for example, choice of drift-correction method) on the adjusted gravity values. Also, an Excel Spreadsheet is available that calculates drift correction and gravity differences between stations.
Southwest Gravity Program Absolute-Gravity Database (updated 2022-07-08)
Procedures for field data collection, processing, quality assurance and quality control, and archiving of relative- and absolute-gravity surveys
Time-lapse gravity data for monitoring and modeling artificial recharge through a thick unsaturated zone
Groundwater response to the 2014 pulse flow in the Colorado River Delta
Gravity change from 2014 to 2015, Sierra Vista Subwatershed, Upper San Pedro Basin, Arizona
Hydrological conditions and evaluation of sustainable groundwater use in the Sierra Vista Subwatershed, Upper San Pedro Basin, southeastern Arizona
Accounting for time- and space-varying changes in the gravity field to improve the network adjustment of relative-gravity data
Initial characterization of the groundwater system near the Lower Colorado Water Supply Project, Imperial Valley, California
Surface and subsurface microgravity data in the vicinity of Sanford Underground Research Facility, Lead, South Dakota
Direct measurement of sub-surface mass change using the variable-baseline gravity gradient method
Results of the first North American comparison of absolute gravimeters, NACAG-2010
Gravity data from the San Pedro River Basin, Cochise County, Arizona
The utility of gravity and water-level monitoring at alluvial aquifer wells in southern Arizona
Use of Microgravity to Assess the Effects of El Nino on Ground-Water Storage in Southern Arizona
Changes in Gravity used to Quantify Groundwater-Storage Change in the Tucson AMA
The Tucson Active Management Area (AMA) is a semi-arid region in southern Arizona. Historically, groundwater pumping in the Tucson AMA exceeded recharge for many decades. Gravity-based methods developed by the USGS can be used to directly measure groundwater-storage changes, providing an estimate of total storage change that does not rely on uncertain estimates of inflows and outflows.