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Application of satellite nadir altimetry for forecasting river flow in transboundary rivers S. Biancamaria 1 ( [email protected] ), F. Hossain 2 , D.P. Lettenmaier 1 , E.A. Clark 1 1 Civil and Environmental Engineering, University of Washington, Seattle WA - PowerPoint PPT Presentation
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Application of satellite nadir altimetry for forecasting river flow in transboundary riversS. Biancamaria1 ([email protected]), F. Hossain2, D.P. Lettenmaier1, E.A. Clark1
1 Civil and Environmental Engineering, University of Washington, Seattle WA2 Civil and Environmental Engineering, Tennessee Technological University, Cookeville TN
H11F-0885AGU Fall Meeting 2010
1. Introduction
Figure 1. In-situ gages (magenta dots), Topex/Poseidon’s virtual stations (red dots) and ground tracks (red lines)
- Ganges and Brahmaputra basins shared between India (upstream) and Bangladesh (downstream).
- Issue: no information on rivers’ state shared between the 2 nations. the farthest upstream point of water level measurement for Bangladesh is at the border.
- Consequence: Bangladesh can forecast water level only 3 days in advance (inadequate for risk managements).
2. Purpose of the study and methodologyPurpose: Use water level anomalies from Topex/Poseidon (T/P) satellite nadir altimeter (from LEGOS-HYDROWEB, Fig. 1 and Table 1) in India and water level anomalies from two gages in Bangladesh (from BWDB/IWM, Fig. 1) to extend forecast lead time.Methodology:I.Compute correlation between in-situ and upstream T/P water level anomalies occurring k days earlier (k=time lag).II.For high correlations, compute in-situ versus time lagged T/P water level anomalies rating curve .III.Use the rating curve to forecast water level anomalies at the gage location from upstream T/P measurements.
T/P Virtual station
River Distance from gage
Numb of obs.
Mean time between obs.
166_1 Brahmaputra 250 km 58 16 days
053_1 Brahmaputra 540 km 38 25 days
242_1 Brahmaputra 550 km 71 14 days
155_1 Ganges 320 km 13 45 days
014_1 Ganges 530 km 25 22 days
079_1 Ganges 680 km 21 29 days
116_2 Ganges 1560 km 49 12 days
116_1 Ganges 1800 km 46 13 days
Table 1. Topex/Poseidon measurements from HYDROWEB
3. Data used- Water level in-situ measurements on the Brahmaputra River at Bahadurabad (Fig. 1) are
available from January 2000 to September 2005. Measurements on the Ganges River at Hardinge Bridge are available from January 2001 to September 2005.
- T/P measurements available from January 1993 to August 2002. T/P repeat period is equal to 10 days, but mean times between 2 obs. in the HYDROWEB time series are higher (Table 1).
- Studied time period: Jan. 2000 to Aug. 2002 (Brahmaputra) and Jan. 2001 to Aug. 2002 (Ganges) + focus on monsoon (June to September) and dry season (October to May).
- Brahmaputra: year 2000 = high discharge, floods in August; year 2001 = lower discharge, no floods; Ganges: year 2001 = “normal” discharge year, no floods (Fig. 2).
Figure 2. In-situ water level and discharge at the gage locations (Fig. 1)
Water level (m, ref. PWD) Discharge (104 m3.s-1)
v
v
v
. .
4. Results- 5-day forecast at Bahadurabad (Brahmaputra) using T/P virtual station 166_1:
- 5-day forecast at Bahadurabad (Brahmaputra) using T/P virtual station 242_1:
- 5-day forecast at Hardinge Bridge (Ganges) using T/P virtual station 014_1:
- 10-day forecast at Hardinge Bridge (Ganges) using T/P virtual station 116_2:
5. Conclusions and perspectives- Nadir altimetry can forecast water level anomalies on the Brahmaputra and Ganges rivers
with RMSE~0.4m for 5-day lead time and with RMSE~0.6-0.8m for 10-day lead time.- Temporal resolution of the forecast could be improved by using data from several nadir
altimeters (like ERS-2, GFO, ENVISAT, JASON-2).- Future wide swath altimetry (like SWOT) should improve detection of floods, which might be
currently missed when using only 1D measurements from nadir altimeters.- Future work: coupling with hydrodynamic model to do some forecasts inside Bangladesh. - Acknowledgements: HYDROWEB (www.legos.obs-mip.fr/en/soa/hydrologie/hydroweb/) for
T/P data; BWDB/IWM for in-situ data.
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10-d
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5-day time lag
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5-day time lag
Forecast RMSE
Forecast RMSE
Forecast RMSE
Forecast RMSE
0 5 10 15 20
1.4
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Time lag (days)
RMSE
in-s
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0 5 10 15 20
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Time lag (days)
RMSE
in-s
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0 5 10 15 20
0 5 10 15 20
1.4
1.21
0.8
0.6
0.40.2
Time lag (days)
RMSE
in-s
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0 5 10 15 20
0 5 10 15 20
1.4
1.21
0.8
0.6
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Time lag (days)
RMSE
in-s
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lti (m
)
0 5 10 15 20
Feb Apr Jun Aug Oct Dec
Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug Oct Dec
22
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10
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5432
10
Danger level
2001Lowest year (2002)Lowest year (2002)Highest year (2003)
Flood level
Danger level
Flood level
20002001
Lowest year (2002)Lowest year (2002)Highest year (2004)
Gan
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Time (years)
III.
III.
III.
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543210
-1-2-32000 2000.5 2001 2001.5 2002
Wat
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Time (years)
543210
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Wat
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Time (years)
6
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Time (years)
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In-situ
5-day forecast
In-situ
5-day forecast
In-situ
5-day forecast
In-situ
10-day forecast
Monsoon+Dry
Dry
Monsoon
Bangladesh
Ganges Bra
hmaputra
India
