Southwest Gravity Program Active
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.
Forecasting Total Dissolved Solids Concentrations of Groundwater from the Lower Colorado Water Supply Project
Aquifer-storage monitoring at Tucson Water’s Heritage Project
Aquifer storage-change monitoring in Albuquerque Basin, New Mexico
Aquifer storage-change monitoring in the Big Chino Subbasin, Yavapai County, Arizona
Monitoring aquifer-storage change at Tucson Water's Southeast Houghton Area Recharge Project
North Phoenix aquifer monitoring with repeat microgravity
Aquifer-Storage Change and Land-Surface Elevation Change Monitoring in the Tucson Active Management Area
Monitoring Network of the Groundwater Flow System and Stream-Aquifer Relations in the Mesilla Basin, Doña Ana County, New Mexico and El Paso County, Texas
- Overview
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).
Sources/Usage: Public Domain. View Media DetailsThe USGS Southwest Gravity Program carries out gravity projects for aquifer-storage monitoring and geologic modeling in California, Arizona, and New Mexico. This map shows the location of 24 projects carried out since 2010. 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.
Sources/Usage: Public Domain. View Media DetailsAs generalized in this image, a gravity measurement is sensitive to a cone-shaped region of the subsurface—as depth increases, the sensitivity to individual water molecules decreases, but the region of sensitivity expands. The result is that for a given height of water-storage change, the corresponding gravity change is the same (1 meter of water=42×10–8 meters per second squared), regardless of whether the water is stored near the land surface or at depth. The amount of gravity change is also independent of the porosity of the aquifer or soil. 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.
- Science
Forecasting Total Dissolved Solids Concentrations of Groundwater from the Lower Colorado Water Supply Project
The USGS seeks to increase understanding of the groundwater system in the vicinity of the Lower Colorado Water Supply Project well field and to estimate future groundwater levels and total dissolved solids concentrations in the wells and the long-term viability of the Lower Colorado Water Supply Project.Aquifer-storage monitoring at Tucson Water’s Heritage Project
Tucson Water’s Santa Cruz River Heritage Project releases up to 3,150 acre-feet a year of reclaimed water into the Santa Cruz River channel near downtown Tucson, AZ, much of which is expected to recharge to the subsurface through the channel bottom. Tracking the movement of recharged water is necessary to limit the dispersal of that water within specific target boundaries, and to enable resource...Aquifer storage-change monitoring in Albuquerque Basin, New Mexico
USGS, in cooperation with the Albuquerque Bernalillo County Water Utility Authority, began repeat microgravity measurements in 2015 to monitor aquifer-storage changes in the Albuquerque basin.Aquifer storage-change monitoring in the Big Chino Subbasin, Yavapai County, Arizona
The Big Chino Subbasin is a groundwater basin that includes the Verde River headwaters in Yavapai County in north-central Arizona. Groundwater in the Big Chino Valley discharges to wells (by pumping), by evapotranspiration, and to the upper Verde River springs, which form the headwaters of the Verde River. Groundwater also discharges to short perennial reaches of Williamson Valley Wash, Walnut...Monitoring aquifer-storage change at Tucson Water's Southeast Houghton Area Recharge Project
The Arizona Water Science Center is monitoring aquifer-storage changes at an artificial recharge facility operated by Tucson Water in southeast Tucson. Aquifer-storage change is monitored by measuring changes in gravity over time at the same network of benchmarks. As water is added or removed from the aquifer, there is a change in mass and a corresponding measurable change in gravity.North Phoenix aquifer monitoring with repeat microgravity
The City of Phoenix has traditionally relied on surface-water supplies from the Salt, Verde, and Colorado River watersheds. To increase water-supply resiliency and flexibility, the City is expanding its Artificial Storage and Recovery (ASR) operations in the north Phoenix area. USGS is measuring small changes in gravity caused by groundwater-storage changes to better understand where and when...Aquifer-Storage Change and Land-Surface Elevation Change Monitoring in the Tucson Active Management Area
The Arizona Water Science Center is monitoring aquifer-storage changes and land subsidence within the Tucson Active Management Area (AMA). Land-surface elevation change is monitored at a network of benchmarks throughout the Tucson AMA by measuring changes in land surface elevation over time (approximately annually) with Interferometric Synthetic Aperture Radar (InSAR). Aquifer-storage change is...Monitoring Network of the Groundwater Flow System and Stream-Aquifer Relations in the Mesilla Basin, Doña Ana County, New Mexico and El Paso County, Texas
The Mesilla Basin monitoring program was established in 1987 to document the hydrologic conditions of New Mexico’s southern-most, Rio Grande rift basin. The program’s data collection and reporting is conducted by the U.S. Geological Survey in cooperation with local, state, and federal agencies. Hydrologic data collected as part of the monitoring program provide valuable information to better... - Data
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