Hydrological modelling of Hydrological modelling of the Ob riverthe Ob river

Sylvain BiancamariaSylvain Biancamaria(1)(1), Nelly Mognard, Nelly Mognard(1)(1), Paul Bates, Paul Bates(2)(2), Aaron , Aaron BooneBoone(3)(3) & Jean-François Cretaux & Jean-François Cretaux(1)(1)

(1) LEGOS, FR(2) University of Bristol, UK(3) CNRM/CNRS, FR

February 1st, 2008February 1st, 2008

Models usedModels used ISBA (Interaction Soil Biosphere Atmosphere) from ISBA (Interaction Soil Biosphere Atmosphere) from

CNRM (spatial resolution 1°x1°) for lateral inflows + CNRM (spatial resolution 1°x1°) for lateral inflows + LISFLOOD-FP, flood inundation model from University of LISFLOOD-FP, flood inundation model from University of Bristol, for the river :Bristol, for the river :

LISFLOOD

Flood plain topography

River centre, width and depth

Manning coefficients (friction) for river and

flood plain

Discharge, water depth and elevation (river & flood plain)

Discharge from Belogorje

gauging station

Incoming flow to the study domain

River modelling

TRIP

Lateral inflow to the river from study domainISBA

LSMRunoff from each pixel

Lateral inflow from the whole river basin

Atmospheric input

Lower Ob (between Belogorje and Salkhard):Lower Ob (between Belogorje and Salkhard):

Legend: Incoming flow (Belogorje) Lateral inflow (ISBA) River (CIA WDB) Gauging station

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Time period: year 1993 (daily discharge at Belogorje only available from 01/01/1993 to 10/31/1994)

Study domainStudy domain

Comparison between modelled and measured discharge at Comparison between modelled and measured discharge at Salekhard as a function of the river depth (Manning Salekhard as a function of the river depth (Manning coefficient=0.015):coefficient=0.015):

Modelled dischargeModelled discharge

Discharge underestimation (~7000 m3/s) -> too weak lateral

inflow (linked with precipitation)

River depth=10m & Manning coefficient=0.015

River depth=15m & Manning coefficient=0.015

TopexVirtual station shown

Comparison between April and October 1993:Comparison between April and October 1993:Comparison Topex/modelled heightComparison Topex/modelled height

Orbit Parameters

Nadir/wide swath selection

Instrument ground location:

Water elevation:

Water elevation at the measurement

points

Instrumental Error(Gaussian noise)

Synthetic SWOT measurement

The synthetic SWOT measurement simulator developped by The synthetic SWOT measurement simulator developped by Noveltis for oceans has been adapted for hydrology:Noveltis for oceans has been adapted for hydrology:

SWOT simulatorSWOT simulator

Use of an Ensemble Kalman Filter to assimilate the synthetic SWOT observations into LISFLOOD.

Model uncertainties represented through an ensemble of model states, generated by perturbing: 1. Precipitation (rain+snow),2. Air temperature,3. River depth+flood plain topography,4. Manning coefficient.

Different Orbits can be tested. It will also be possible to assess how SWOT will improve the modelling compared to the use of only nadir data.

AssimilationAssimilation