Terrestrial water storage change from temporal gravity variation

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Terrestrial water storage change from temporal gravity variation

Shaakeel Hasan

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Terrestrial water storage change from temporal gravity variation

Shaakeel Hasan

Terrestrial water storage change from temporal gravity variation

Shaakeel Hasan

Promotoren: Prof. dr. ir. P.A. Troch Hoogleraar Hydrologie en Kwantitatief Waterbeheer (1999–2005),Wageningen Universiteit en Professor of Hydrology and Water Resources Professor of Civil Engineering and Engineering Mechanics University of Arizona (Tucson, AZ, USA) Prof. dr. ir. R. Uijlenhoet Hoogleraar Hydrologie en Kwantitatief Waterbeheer Wageningen Universiteit Promotiecommissie: Prof. Prof. Prof. Prof. Dr.-Ing. habil. R. Klees, Technische Universiteit Delft dr. ir. H.H.G. Savenije, TechnischeUniversiteit Delft dr. ir. M.F.P. Bierkens, Universiteit Utrecht dr. ir. S.E.A.T.M. van der Zee, Wageningen Universiteit

Dit onderzoek is uitgevoerd binnen de onderzoekschool SENSE

Terrestrial water storage change from temporal gravity variation

Shaakeel Hasan

Proefschrift ter verkrijging van de graad van doctor op gezag van de rector magnificus van Wageningen Universiteit, Prof. dr. M.J.Kropff, in het openbaar te verdedigen op maandag 27 april 2009 des namiddags te vier uur in de Aula.

Shaakeel Hasan, 2009 Terrestrial water storage change from temporal gravity variation Ph.D. thesis, Wagneingen University, Netherlands With summaries in English and Dutch ISBN 978-90-8585-385-5

Abstract

Recent progress in accurately monitoring temporal gravity variations by means ofsuperconducting gravimeters and satellite geodesy provides unprecedented opportunities in closing the water balance. This thesis deals with the relation between temporal gravity variation and water storage change. A superconducting gravimeter observes with high accuracy (few nm/s2 ) and high frequency (1 Hz) the temporal variations in the Earth’s gravity field, in Moxa, Germany. Hourly gravity residualsare obtained by time-averaging and correcting for Earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals are significantly affected by hydrological processes (interception, infiltration, surface runoff and subsurface redistribution) in the vicinity of the gravimeter. First, time series analysis and distributed hydrological modeling techniques wereapplied to investigate the effect of hydrological processes on observed terrestrial gravity residuals. It is shown that the short-term response of gravity residuals to medium to heavy rainfall events can be efficiently modeled by means of a linear transfer function. This transfer function exhibits an oscillatory behavior that indicates fast redistribution of stored water in the upper layers(interception store, root zone) of the catchment surrounding the instrument. The relation between groundwater storage and gravity residuals is less clear and varies according to the season. High positive correlation between groundwater and gravity exists during the winter months when the freezing of the upper soil layers immobilizes water stored in the unsaturated zone of the catchment. Similar results arefound in the application of a distributed hydrological model to detect gravity variation. Observed gravity change is then considered as an integrator of catchmentscale hydrological response (similar in nature to discharge measurements), and therefore used to constrain catchment-scale hydrologic models. Results indicate that a lumped water balance model for unsaturated storage and fluxes, coupledwith a semi-distributed hydraulic groundwater model for saturated storage and fluxes, successfully reproduces both gravity and discharge dynamics. v

Since its launch, the Gravity Recovery and Climate Experiment (GRACE) mission has been providing estimates of surface mass anomalies for the entire globe. Despite the coarse spatial (a few hundred kilometers) and temporal (1 month) resolution, the...