HR: 1340h
AN: G43B-1212    [Abstracts]
TI: GPS observation of compaction or expansion of the Perth basin aquifer system
AU: * Jia, M
EM: minghai.jia@ga.gov.au
AF: Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
AU: English, P
EM: pauline.english@ga.gov.au
AF: Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
AU: Commander, P
EM: philip.commander@water.wa.gov.au
AF: Department of Water, PO Box K822D, Perth, WA 6842, Australia
AU: Johnston, G
EM: gary.johnston@ga.gov.au
AF: Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
AB: Solutions from reprocessing over ten years (1997-2006) of continuous GPS (CGPS) data from the Australia region using absolute GPS satellite antenna and receiver antenna phase correction models in the latest IGS05 reference frame (the IGS realisation of the ITRF2005 reference frame) have made estimation of vertical velocity at a resolution of 1mm/yr practicable. The accuracy of CGPS vertical velocity can reliably detect a small vertical land motion caused by groundwater level change in response to prolonged periods of groundwater pumping and recharge. Three CGPS sites, namely HAL1 (Hillary), PERT (Perth) and YAR2 (Yarragadee) located in the Perth Basin in Western Australia, record subsidence of 5mm/yr (in HIL1 and PERT) and uplift of 2mm/yr (in YAR2). These changes are all statistically significant using different short memory and long memory time series noise models. The key source for the changes is correlated with groundwater levels. In the Perth metropolitan area, potentiometric head in the confined aquifers has declined significantly over the past decade in response to high groundwater extraction rates due to drought conditions. The GPS vertical velocity in HIL1 and PERT reflects elastic compaction of the aquifer system. In agricultural areas north of Perth, such as typified by the location of YAR2 CGPS station, groundwater levels have risen by as much as 0.4m/yr during recent decades. This is due to increased recharge through replaced perennial native vegetation by annual pasture and crops. Accordingly, upward GPS vertical velocity in YAR2 may reflect vertical expansion of strata in the semi-confined aquifer system. In addition, the significant annual signal in YAR2 is strongly correlated to the seasonal rainfall change in the region.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1241 Satellite geodesy: technical issues (6994, 7969)
DE: 1243 Space geodetic surveys
DE: 1829 Groundwater hydrology
DE: 1880 Water management (6334)
SC: Geodesy [G]
MN: 2007 Fall Meeting