Retrieving Soil Moisture States Using Streamflow Data

Assimilation C. Rüdigera

Supervisors:Jeffrey P. Walkera, Jetse D. Kalmab,

Garry R. Willgoosec

a Dept. of Civil & Env. Eng., University of Melbourne, Australia

b School of Engineering, University of Newcastle, Australia

c School of Geography, University of Leeds, United Kingdom

Christoph Rüdiger

Postgrad Seminar 2004

Koster et al., JHM, 2000

Christoph Rüdiger

Postgrad Seminar 2004

Christoph Rüdiger

Postgrad Seminar 2004

Goulburn Catchment

Melbourne

NewcastleSydney

1000km0km

Christoph Rüdiger

Postgrad Seminar 2004

Goulburn Catchment

Streamgauge

Soil Moisture

Climate

www.civenv.unimelb.edu.au/~jwalker/data/oznet/

Christoph Rüdiger

Postgrad Seminar 2004

Catchment Land Surface Model

Koster et al., JGR, 2000Saturation

Depth

Water Table

Eq. profile

Moisture Deficit

D = 0

D = smallD = large

Prognostic variables:

•Catchment Deficit

•Surface Moisture Excess

•Root Zone Excess

Christoph Rüdiger

Postgrad Seminar 2004

Internal routing

Travel time TpiVelocity weight v-1

Unit Hydrograph for Catchment

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Christoph Rüdiger

Postgrad Seminar 2004

Synthetic ExperimentVariational Data Assimilation

model outp

ut

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assimilation step

NLFIT (Kuczera, WRR, 1982)

• “Truth”:– 10yr spin up– 1yr full run

• “Experiment 1”:– One month only– Degraded soil moisture values (low catchment deficit)

• “Experiment 2”:– “Openloop 1” and changed forcing (33% lower radiation and

20% higher precipitation)

Christoph Rüdiger

Postgrad Seminar 2004

Results from assimilation with "true" forcing (runoff)

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Results “Experiment 1”

Discharge Soil Moisture

Christoph Rüdiger

Postgrad Seminar 2004

Results “Experiment 1”Results from assimilation with "true" forcing (runoff)

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Christoph Rüdiger

Postgrad Seminar 2004

Results form assimilation with "wrong" forcing data (runoff)

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Results form assimilation with "wrong" forcing data (runoff)

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Results form assimilation with "wrong" forcing data (runoff)

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Results form assimilation with "wrong" forcing data (profile mc)

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Results “Experiment 2”

Discharge Soil Moisture

Christoph Rüdiger

Postgrad Seminar 2004

Results “Experiment 2”Results form assimilation with "wrong" forcing data (runoff)

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Christoph Rüdiger

Postgrad Seminar 2004

Conclusion from Results

• Results show that runoff has useful information about soil moisture states

• Problems in semi-arid regions, when overestimation of water input due to degraded forcing data (potentially for too dry, as well!?)

• Monthly assimilation windows have positive impact, reduction of assimilation window should improve results further

Christoph Rüdiger

Postgrad Seminar 2004

Future Work

• Including inter-catchment routing• Comparison of different climates

(real data)• Assimilation of surface soil moisture

Christoph Rüdiger

Postgrad Seminar 2004

Acknowledgments• Australian Research Council (ARC-DP grant

0209724)• Hydrological Sciences Branch, National

Aeronautics and Space Administration (NASA), USA

• University of Melbourne – Melbourne International Fee Remission

Scholarship (MIFRS)– Postgraduate Overseas Research Experience

Scholarship (PORES)