J. Famiglietti1, T. Syed1, P. Yeh1,2 and M. Rodell3

1Dept. of Earth System Science, University of California,Irvine, USA2now at: Institute of Industrial Science, University of Tokyo3Hydrological Sciences Branch, NASA Goddard Space Flight Center, Greenbelt, MD, USA

in collaboration with

D. Chambers, University of Texas at AustinF. Frappart, University of California, Irvine

S. Nerem, University of Colorado

S. Swenson, National Center for Atmospheric Research

I. Velicogna, University of California, Irvine

J. Wahr, University of Colorado

Terrestrial and Global Hydrology from Satellite Observations of Time-Variable Gravity

New applications and understanding of terrestrial and global hydrology

•Groundwater storage variations

•Estimating regional and global discharge

•Emerging trends in terrestrial hydrology

•Mass changes in Earth’s global water reservoirs

Overview

Groundwater Storage Changes Using GRACE

SLAND = SSNOW + SSW + SSM + SGW

SGW SLAND - SSNOW - SSW - SSM

Remove this (SSNOW

+ SSW + SSM) from SLAND…

To isolate this (SGW )

SLAND

-8

-6

-4

-2

0

2

4

6

Jan-02Apr-02Jul-02Oct-02Jan-03Apr-03Jul-03Oct-03Jan-04Apr-04Jul-04Oct-04Jan-05Apr-05Jul-05

Water Storage (cm)

Mississippi River basin

Illinois

GRACE groundwater estimate

Groundwater well observations

GRACE groundwater estimates (smoothed)

Yeh et al., 2006

Rodell et al., 2006

Groundwater Storage Changes Using GRACE

Swenson et al., 2007, to appear

Groundwater Storage Changes Using GRACE

Terrestrial water balance

SLAND = P - E- R

Atmospheric water balance

W = E - P - divQ

Coupled land-atmosphere water balance

R = SLAND - W - divQ

SLAND: storage change (dS/dt)

P: precipitation

E: evaporation

R: discharge

W: precipitable water storage change (dW/dt)

divQ: horizontal water vapor divergence

•Previously had to assume that SLAND = 0 and apply at annual time scales

•Now we have SLAND so we can compute monthly time series

Freshwater Discharge Estimation Using GRACE

(a) Lena (a) Lena

(b) Ob(b) Ob

(c) Yenisei(c) Yenisei

(d) Mackenzie(d) Mackenzie

Lena

Entire Pan-Arctic

Syed et al., 2007b

Pan-Arctic discharge estimates

Freshwater Discharge Estimation Using GRACE

Significance of Pan-Arctic discharge estimates:

•Covers entire Pan-Arctic region, including ungauged regions

•Larger than previous scaled, gauge-based estimates for the equivalent time period

•Implications are that discharge is larger than could be anticipated by scaling up gauge measurement, or that discharge in that region is accelerating, or both

Freshwater Discharge Estimation Using GRACE

Syed et al., 2007c

Drainage region discharge estimates

Freshwater Discharge Estimation Using GRACE

Syed et al., 2007c

Continental discharge estimates

Freshwater Discharge Estimation Using GRACE

Syed et al., 2007c

•Land-based and ocean-based estimates agree well

•Both are well within range of previous estimates

•Global water balance closure to about 5%

•Trend (0.5 mm/yr sea level equivalent) has implications for closing GMSLR budget

Global discharge estimates

Freshwater Discharge Estimation Using GRACE

Interannual Variations and Trends in Terrestrial Hydrology from GRACE, 2002-2007

Annual Amplitude (cm) Trend (cm/yr)

•First global look at magnitude of water storage variations•Reveal important information on storage that is typically not captured by models: glacial melt, reservoir release, groundwater mining, etc.

• Important trends emerging•Data are ripe for understanding hydroclimatological variations as well as for data assimilation and for pointing to model enhancements

Interannual Variations and Trends in Terrestrial Hydrology from GRACE, 2002-2007

Interannual Variations and Trends in Terrestrial Hydrology from GRACE, 2002-2007

Mass Variations in Earth’s Global Water Reservoirs

SGLOBAL = SOCEAN + SLAND + SICE + SATM = 0

We can now track ocean, land and ice changes using a single observing system

Monthly storage anomalies as equivalent mean sea level

SOCEAN + SLAND + SICE + SATM = SGLOBAL = 0

Trends (mm/yr)

Ocean = 0.35 mm/yr

Land = 0.57 mm/yr

Greenland = -0.58 mm/yr

Antarctica = -0/34 mm/yr

Mass Variations in Earth’s Global Water Reservoirs

Summary

•Groundwater storage changes from GRACE are feasible and will improve with improved ancillary data, e.g. remotely sensed snow, surface water and soil moisture.

•Freshwater discharge estimation from GRACE is currently the only observation-based way to estimate global discharge

•Emerging trends in continents and global land-ocean-ice demonstrate GRACE capabilities to monitor water storage changes from a single observing system and can help make the case for continuity in the mission

Posters

Groundwater

Comparison of Simulated Groundwater Storage Variations to In Situ Observations and GRACE Terrestrial Water Storage Variations, M. Lo, P. Yeh and J. Famiglietti

Discharge

Large-Scale Terrestrial Freshwater Discharge Estimation using GRACE, T. Syed, J. Famiglietti, D. Chambers and M. Rodell

Decomposition of total water storgage into surface and subsurface components

Interannual Variations of River Water Storage from a Multiple Satellite Approach: A case study for the Rio Negro River basin, F. Frappart, F. Papa, J. Famiglietti, C. Prigent, W.B. Rossow, F. Seyler