USGS Monthly Groundwater News and Highlights: October 1, 2018
Feature: How Changes in Earth's Gravity Reveal Changes in Groundwater Storage
Figure: As 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. Source: Kennedy, 2018. Figure is in the public domain.
Changes in the amount of water stored in aquifers cause small changes in Earth's gravitational field. Since the 1980s, the USGS has developed field methods, software, and analytical procedures for using gravity data to aid in groundwater studies. When the amount of groundwater in an aquifer changes, either by recharge or by discharge to surface water or wells, the gravitational acceleration at the land surface also changes. This very small change is detectable with highly precise instruments. The measurements allow scientists to map changes in groundwater storage. Gravity changes can also be measured by satellites, which provide an average value of water-storage changes over several thousand square kilometers. While these data sources are complementary, land-based measurements provide finer spatial resolution at the local or regional scales that resource managers typically need to inform groundwater management and planning decisions. Learn more about the USGS's Southwest Gravity Program.
USGS Groundwater-Related Technical Announcements
USGS Seeks National Ground-Water Monitoring Network Proposals for 2019
The USGS Active Groundwater Level Network includes about 20,000 wells that have been measured by the USGS or USGS cooperators at least once within the past 13 months. The animation shows a daily snapshot of water-level statistics in the network for September 2018. Credit: USGS. The image is in the public domain.
USGS Groundwater-Related Publications
Groundwater contributions to excessive algal growth in the East Fork Carson River, Carson Valley, west-central Nevada, 2010 and 2012 (09/28/18)
Williston Basin groundwater availability, United States and Canada (09/27/18)
Groundwater availability of the Williston Basin, United States and Canada (09/28/18)
Groundwater salinity mapping using geophysical log analysis within the Fruitvale and Rosedale Ranch oil fields, Kern County, California, USA (09/26/18)
Deciphering the dynamics of inorganic carbon export from intertidal salt marshes using high-frequency measurements (09/26/18)
Comparing public-supply and shallow aquifer groundwater quality in the North San Francisco Bay Aquifers, California (09/25/18)
Four-dimensional isotopic approach to identify perchlorate sources in groundwater: Application to the Rialto-Colton and Chino subbasins, southern California (USA) (09/20/18)
Geochemical conditions and nitrogen transport in nearshore groundwater and the subterranean estuary at a Cape Cod embayment, East Falmouth, Massachusetts, 2013-14 (09/20/18)
New insights into surface-water/groundwater exchanges in the Guadalupe River, Texas, from floating geophysical methods (09/19/18)
Weathering of oil in a surficial aquifer (09/14/18)
Continuing progress toward a national assessment of water availability and use (09/12/18)
Changes in Earth's gravity reveal changes in groundwater storage (09/12/18)
Selected trace-elements in alluvium and rocks, western Mojave Desert, southern California (09/10/18)
Tidal flushing of mercury from the Bremerton Naval Complex through the PSNS015 stormwater drain system to Sinclair Inlet, Kitsap County, Washington, 2011-12 (09/07/18)
Documentation of single-well aquifer tests and integrated borehole analyses, Pahute Mesa and Vicinity, Nevada (09/05/18)
Interstate water management of a "hidden" resource - Physical principles of groundwater hydrology (09/02/18)
Geologic framework for the national assessment of carbon dioxide storage resources -- Atlantic Coastal Plain and Eastern Mesozoic Rift Basins (09/19/18)
Intensities, aftershock sequences, and the location of the 1936 Milton-Freewater earthquake near the Oregon-Washington border, U.S.A. (09/27/18)
USGS Groundwater Flow and Transport Model Data Releases
Note: The following links take you to data.doi.gov
MODFLOW-NWT datasets for simulations of groundwater and surface-water in the Great Dismal Swamp of Virginia and North Carolina
MODFLOW-2005 model archive for simulation of zones of groundwater contribution to wells south of the Naval Weapons Industrial Reserve Plant in Bethpage, New York
MODFLOW-2000 and MODPATH models for simulations used to delineate contributing areas for 2017 pumping conditions to selected wells in Ingham County, Michigan
A finite-difference algorithm used to simulate one-dimensional diffusion and adsorption of trichloroethene in a rock matrix
MODFLOW-NWT model scenarios used to evaluate potential effects of proposed drainage modifications on groundwater discharge in the vicinity of Long Lake, Indiana Dunes National Lakeshore, near Gary, Indiana
In these photos, USGS Research Hydrologist Jeff Kennedy is making measurements of very small changes in the earth's gravity field to help us understand changes in groundwater storage. The yellow gravity meter in the top photo is an absolute-gravity meter, which provides a direct measurement of the absolute force of gravity at a location. The silver gravity meter in the second photo is a relative-gravity meter, which can measure small differences in gravity as the meter is moved from place to place.
Credit: USGS. Photo is in the public domain. Click on photo for larger version.
Credit: USGS/Michael Landrum. Photo is in the public domain. Click on photo for larger version.