HR: 1340h
AN: H23A-1106    [Abstracts]
TI: Using Relative Gravity Measurements to Monitor Transient Infiltration
AU: * Barnes, F
EM: fbarnes@hwr.arizona.edu
AF: University of Arizona, 1133 E. North Campus Drive, Tucson, AZ 85721-0011
AU: Ferre, P
EM: ty@hwr.arizona.edu
AF: University of Arizona, 1133 E. North Campus Drive, Tucson, AZ 85721-0011
AB: Ground based microgravimetry has shown great promise for monitoring changes in water storage in deep vadose zones. The ability of the method to make noninvasive, nondestructive measurements of subsurface water storage makes it ideal for watershed-scale hydrologic monitoring. However, in many environments with deep vadose zones, areas associated with large changes in water storage are also associated with large changes in water content throughout the vadose zone. This presents a potential limitation to gravity methods due to the spatial sensitivity of the methods, which decreases as the inverse depth of the location of water content change squared. In this study, we examine the effects of changes in water storage in the vadose zone on the response of surface based gravimeters. Specifically, we model the response of gravimeters to infiltration and drainage beneath an ephemeral stream. We show that without proper analysis, changes in water storage in the vadose zone can cause very large errors in the interpretation of gravity measurements. However, with more complete analysis and higher temporal resolution of the gravity signal than is commonly acquired, gravity measurements can be corrected and can even be used to characterize effective unsaturated flow parameters. The results of this study point to the importance of combining geophysical and hydrologic understanding in the use and interpretation of hydrogeophysical methods.
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting