HR: 12:10h
AN: H21F-08    [PDF]
TI: Estimating aquifer properties using time-lapse, high precision gravity surveys and groundwater modeling
AU: * Keating, E
EM: ekeating@lanl.gov
AF: Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM 87545 United States
AU: Cogbill, A H
EM: ahc@lanl.gov
AF: Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM 87545 United States
AU: Ferguson, J F
EM: ferguson@utdallas.edu
AF: University of Texas at Dallas, Center for Lithospheric Studies, Richardson, TX 75083 United States
AB: In the past, gravity methods have had limited application for monitoring aquifers, primarily due to the poor drift characteristics of relative gravimeters, which made long-term gravity studies of aquifers prohibitively expensive. Recent developments in portable, very accurate, absolute gravity instruments having essentially zero long-term drift have reawakened interest in using gravity methods for hydrologic monitoring. Such instruments have accuracies of 7 microGals or better and can acquire measurements at the rate of better than one station per hour. Theoretically, temporal changes in gravity can be used to infer storage characteristics and fluxes into and out of the aquifer. The sensitivity of the method to scaling effects, temporal lags between recharge/discharge and changes in storage, and to uncertainties in aquifer structure are poorly understood. In preparation for interpreting a basin-scale, time-lapse gravity data set, we have established a network of gravity stations within the Espanola Basin in northern New Mexico, a semi-arid region which is experiencing rapid population growth and groundwater resource use. We are using an existing basin-scale groundwater flow model to predict changes in mass, given our current level of understanding of inflows, outflows, and aquifer properties. Preliminary model results will be used to examine scaling issues related to the spatial density of the gravity station network and depths to the regional water table. By modeling the gravitational response to water movement in the aquifer, we study the sensitivity of gravity measurements to aquifer storage properties, given other known uncertainties in basin-scale fluxes. Results will be used to evaluate the adequacy of the existing network and to modify its design, if necessary.
DE: 1812 Drought
DE: 1829 Groundwater hydrology
DE: 1884 Water supply
SC: Hydrology [H]
MN: 2003 Fall Meeting