Gravity

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...

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.

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...

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.

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...

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.

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...

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...

Gravity is a measurement of 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 over time, through processes such as infiltration of rainfall or aquifer recharge...