Gravimetry as a tool for hydrologic research at the...
Transcript of Gravimetry as a tool for hydrologic research at the...
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Gravimetry as a tool for hydrologic research
at the Sutherland Observatory
Andreas Güntner, Christoph Förste, Theresa BlumeGFZ German Research Centre for Geosciences
Gaathier Mahed, Maarten De Wit, Moctour DoucoureAEON / University of Cape Town
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Quantifying variations in continental water storage
� Local to global water balances
� Water resources
� Flood risks
P: PrecipitationE: EvapotranspirationR: Runoff∆∆∆∆S: Water storage change
P = E + R + ∆S
Continental water balance
and their changes
in space and time
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Motivation
Quantifying variations in continental water storage
Several storage components in ∆S:
• Snow and ice
• Groundwater
• Soil moisture
• Surface water storage
P: PrecipitationE: EvaporationR: Runoff∆∆∆∆S: Water storage change
Continental water balance
∆S = P – E – R∆S
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GRACE satellite mission
(Gravity Recovery andClimate Experiment)
• Launched in March 2002
Water storage variations from satellite gravimetry
• Launched in March 2002
• Monitoring of temporal variations of the gravity fi eld of the Earthcaused by mass transport processes in the
- Earth's interior
- Atmosphere
- Oceans
- Ice caps
- Continental hydrology
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Orders of magnitude of the different components of the gravity of the Earth:
g =9.807246731…m/s2
Static mass inhomogeneitiesMass changes
9.807246731…m/s• relativity, 1mm height difference
• ocean topography, polar motion
• hydrology (water storage changes)
• Earth and ocean tides, 1m height difference
• large water reservoirs
• mass inhomogeneities in the inner Earth
• mountains, deep ocean trenches, 1km height difference
• Earth flattening and rotation
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Water storage variations on the continents from GRACE
ITG (Bonn) GRACE 2010 daily
Kalman smoother solutions
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Geoid height changes
Linear Trends over 4 years
(2002 - 2006, expressed in cm water column)
+12 cmGlacier melting
in Alaska
Glacier melting
in Greenland
Sumatra earthquake 2004
Postglacial Uplift
Postglacial Uplift
Temporal gravity changes measured by GRACE
0
-12 cmSource: CNES/GRGS Toulouse
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Depletion of groundwater resources in North-West In dia from GRACE(Indian States Rajasthan, Punjab and Haryana, 450 0 00 km²)
Rodell et al. (2009), Nature
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Example Orange River Basin
GRACE data
Global hydrological models
Water storage variations from GRACE satellite gravi metry
Global hydrological models
Spe
iche
rano
mal
ien
(mm
)
Gravimeter Sutherland
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Time-variable gravity data for hydrology
| Andreas Güntner | GFZ German Research Centre fo r GeosciencesGravimetric data in hydrology | 10
�Temporal variations of the gravity field of the Earth
�Water mass variations on the continents after removal of other mass components ∆∆∆∆S: Water storage change
P: PrecipitationE: EvaporationQ: Runoff
∆S = P - Q - E
Only integrative and large-scale measurement of ∆S for hydrology
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Water storage variations from time-variable gravity
precipitation
evapotranspiration
GRACE
Gravimeter
surface runoff
Subsurface runoff
infiltration
goundwater storage variations
snow coverage and melt
soil moisture variations
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Superconducting gravimeters
Superconducting gravitmeters allow
for extremly precise monitoring of
local gravity changes
Accuracy: ~ 10-12 g (1 nanoGal)
→ Measurement of temporal gravity
variations caused by e.g.
soil moisture and groundwater levelsoil moisture and groundwater level
changes
Superconducting
sphere
Superconducting
coils
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Superconducting gravitmeters allow
for extremly precise monitoring of
local gravity changes
Accuracy: ~ 10-12 g (1 nanoGal)
→ Measurement of temporal gravity
variations caused by e.g.
soil moisture and groundwater level
Superconducting gravimeters
soil moisture and groundwater level
changes
gravimeter
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World wide Superconducting gravimeter networkWithin the Global Geodynamic Project (GGP) of the IAG
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GFZ Superconducting gravimeter station in Sutherland (South Africa)
• Since 2000• At the campus of the South African Astronomical Observatory (SAAO)• In cooperation with the National Research Foundation (NRF)
Part of the South African Geodynamic Observatory (SAGOS)
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GFZ Superconducting gravimeter station in Sutherland (South Africa)
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GFZ Superconducting gravimeter station in Sutherland (South Africa)
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Hydrological monitoring in Sutherland / South Afric a
Climate
Gravimeter
Soil moisture
Groundwater Runoff
Climate
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Effects of local water storage variations on gravim eter
Example station Wettzell, Germany
Snow
Soil 0-30cm
Soil 30-150cm
Saprolith 1.5 – 11m
Groundwater > 11m
Creutzfeldt et al., 2010, WRR; Creutzfeldt et al., GJI, 2010
Hydrological gravity effect
Gravimeter residuals
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Examplegravimeter stations in Europe
Water storage variations from gravimeters and GRACE
GRACE
Hydrological modelGravimeter
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Use of gravity data in hydrology - Summary
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Gravimetry as a tool for hydrologic research
at the Sutherland Observatory
Andreas Güntner, Christoph Förste, Theresa BlumeGFZ German Research Centre for Geosciences
Gaathier Mahed, Maarten De Wit, Moctour DoucoureAEON / University of Cape Town