HR: 1340h
AN: H23A-1108    [Abstracts]
TI: Gravity Monitoring of Ground-Water Storage Change in the Southwestern United States
AU: Winester, D
EM: daniel.winester@noaa.gov
AF: NOAA - National Geodetic Survey, Table Mtn. Gravity Observatory 8600 North 39th Street, Longmont, CO 80503 United States
AU: * Pool, D R
EM: drpool@usgs.gov
AF: USGS - Water-Resources Division, 520 North Park Ave., Tucson, AZ 85719 United States
AU: Schmerge, D L
EM: schmerge@usgs.gov
AF: USGS - Water-Resources Division, 520 North Park Ave., Tucson, AZ 85719 United States
AU: Hoffmann, J P
EM: jphoffma@usgs.gov
AF: USGS - Water-Resources Division, 520 North Park Ave., Tucson, AZ 85719 United States
AU: Keller, G R
EM: keller@utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AB: Repeat measurements of absolute gravity have been made since 1998 to estimate changes in ground-water mass as part of ground-water budget estimates in arid and semiarid regions of the Southwestern United States. The absolute acceleration of gravity is measured twice each year at 16 stations to an accuracy of about plus or minus 2 microGal, or about 5 cm of water. Observations are normally done for the purpose of providing gravity control for relative gravity surveys of networks of stations across wider areas. Other data incorporated into the ground-water budget estimates include precipitation, water levels, moisture content in the unsaturated zone, surface water runoff, and ellipsoid heights using the Global Positioning System (GPS). Gravity and water-level changes are correlated for stations measured in the Basin and Range Physiographic Province near Tucson, Phoenix, Casa Grande, and Sierra Vista, Arizona. Decreasing gravity and water levels in the Tucson area since the summer of 1998 are likely related to predominant drought conditions and decreases in ground-water storage following above average winter precipitation and recharge during the El Nino of 1998. Increases in gravity at stations in the upper and middle Verde Valley Watershed in central Arizona since the fall of 2000 do not correlate well with declining streamflows and water levels and may be caused by temporary increases in soil moisture following wet winters. There have been no significant observed gravity changes at two stations in the El Paso, Texas, area since the initial observations during the summer of 2003, even though ground-water pumping in the area has been heavy.
DE: 1812 Drought
DE: 1829 Groundwater hydrology
DE: 1884 Water supply
DE: 1244 Standards and absolute measurements
DE: 0920 Gravity methods
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting