by F. Annor, N. van de Giesen, T. Bogaard and D. Eilander Presented at the Final Volta Basin Development Challenge Science Workshop, September 2013

1. A Partner
of
Monitoring Small Reservoirs in the
Volta Basin of Ghana
Frank Annor, Nick van de Giesen, Tom Bogaard & Dirk Eilander
(f.o.annor@tudelft.nl)
CPWF Scientific Workshop , 17-19 September 2013, Ouagadougou, Burkina Faso

2. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Content
1. Main message & Background
2. Methodology
3. Preliminary results & Discussions
4. Outlook

3. MAIN MESSAGE & BACKGROUND

4. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Main message
© pubs.usgs.gov
12mm/day
9mm/day
1.4mm/day
end of June
Feb. - March

5. 5
The Volta River System
≈400,000 Km2
UER = 8,570 km2
RF 500 (N)-1100 (S)mm/yr

6. Andes • Ganges • Limpopo • Mekong • Nile • Volta
How can we bridge the poverty gap?

7. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Small Reservoirs – multiple uses
Farming
 Rain-fed – not enough (1970s -1980s
Drought!)

8. Andes • Ganges • Limpopo • Mekong • Nile • Volta
What are the issues with SR?
 Lack of adequate storage facilities (design &
capacity problems!) & productive use of existing
facilities
 Large (?) Evaporation losses
 Sedimentation not really a problem – 3400t/year

9. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Monitoring network
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1,244
18,780
24,927
11,359
23,033
62,010
6,309
27,993
7,052
Area per WMO Station in km²
Data: Deutscher Wetterdienst (2008)

10. Monitoring network - TAHMO

11. METHODS

12. Methodology
Satellite &
GPS
Ground
Measurements
Reservoir
Masks
BEAM
ILWIS, ERDAS WS + ECS Isotopes
variables
Evap – EBM
(heat fluxes, Ef) Evap - ECS Evap - WB
Satellite
Imagery
Retrieval
of
variables

13. Monitoring - Satellite
Evaporation
SN Satellite Data
Spatial
resolution
Geo-biophysical
Variables to be
retrieved Dates
Data
availability Source
1MERIS 260m
LST & NDVI,
Emissivity, Albedo
Mar-11 to Mar 2012 √ ESA
2AATSR 1km
LST & NDVI,
Emissivity
Mar-11 to Mar 2012 √ ESA
3
Landsat 7 ETM+
(8) 30m, 60m
LAI, LST, NDVI,
Emissivity, Albedo Mar-07 to Mar 2012; 2013 √X ESA/USGS
4ASTER 15, 30,90m
LAI, LST, EVI,
Emissivity, Albedo Mar-11 to Mar 2012 √ USGS (NASA)
5Sentinel - 2 20m (?)
LAI, LST, NDVI,
Emissivity ? X ESA
Water Mask and Water Monitoring
1Landsat 30m Mar-92 to Mar 2012 √ ESA/USGS
2Radarsat-2 < 7m Nov-12 to Present √ CSA
3
ENVISAT
(ASAR) 30m Mar-07 to Mar 2012 √ ESA
4ALOS 7m ? √ JAXA
5SPOT 10m ? √ ESA

14. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Issues - RS Evaporation estimates
L - Avg. RMSE of 50Wm-2 & 15 – 30% RE
Physical and Analytical methods are not better than
empirical and statistical approaches
Empirical methods are limited by in-situ training data
Diurnal variation of evaporation vrs instantaneous
measurements with RS (Bowen Ration & evaporative
fraction)
Temporal & Spatial Scaling issues (extrapolation, gap
filling & data fusion) + clouds
Surface energy models (SEBAL, SEBS etc.)
Kalma et al. (2008) & Farah et al. (2004)

15. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Base Map & Radar monitoring
Landsat SPOT
ASAR, ALOS & Radarsat-2
Radar MonitoringOptical – base map
Growing MLC - automation
NIR & visible wavelengths Intensity - Roughness & Polarisation

16. Fieldwork
0
2
4
6
8
10
12
Area [ha]

17. Fieldwork
SR154
SR120

18. RADARSAT-2 SAR imagery
SR154, Pauli decomposition
RGB Composition:
R: Single Bounce
G: Volume Scattering
B: Double Bounce
RGB composition RGB comp [3x3 window]
Single Bounce
A
Double bounce
C
Volume Scattering
B

19. Andes • Ganges • Limpopo • Mekong • Nile • Volta
One temporal prior for
previous and two for
subsequent classifications.
Subsequent is dependent
on rain / dry season.
Based on 3 pix moving
average
Growing way of filtering
unclassified pixels/
removing water and land
‘islands’
SR Delineation
WOIS

20. 20
Storage - Bathymetry
0
1
2
3
4
5
6
0
10,000
20,000
30,000
40,000
50,000
Depth(m)
Area(m2)
Volume (m3)
Area Depth
Volume = 0.00857 x Area1.4367 m3

21. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Time Series of SR – Mass balance
21
Small Reservoir
Storage (S)
Seepage
EvaporationRainfall
IrrigationRunoff
≈ 0 ?
Onset of the dry season - Nov

22. PRELIMINARY RESULTS &
DISCUSSIONS

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Time series of SR …1

24. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Time series of SR …2
26 Reservoirs
Weather Station @
Binaba (Telemetry)

25. Measurements (ECS + WS + L)
Instrumentation

26. -160
-140
-120
-100
-80
-60
-40
-20
0
20
11/17/2012
11/21/2012
11/25/2012
11/29/2012
12/3/2012
12/7/2012
12/11/2012
12/15/2012
12/19/2012
12/23/2012
12/27/2012
12/31/2012
1/4/2013
1/8/2013
1/12/2013
1/16/2013
1/20/2013
1/24/2013
1/28/2013
2/1/2013
2/5/2013
2/9/2013
2/13/2013
2/17/2013
2/21/2013
2/25/2013
3/1/2013
3/5/2013
3/9/2013
MW_Upstream MW_Midstream MW_Downstream Lake
Water Level Fluctuations

27. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Water Balance of SR
27
Isotopes

28. Evaporation
0
1
1
2
2
3
3
4
0
5
10
15
20
25
30
35
40
11/11/2012 12/11/2012 1/11/2013 2/11/2013 3/11/2013 4/11/2013 5/11/2013 6/11/2013
WindSpeed(m/s)
Evaporation(mm/day)
Temperature(oC)
Date
Evaporation Temperature (atm) Wind Speed
Avg - 9mm/day
Min - 1.4mm/day
Max - 12mm/day

29. OUTLOOK

30. Andes • Ganges • Limpopo • Mekong • Nile • Volta
Outlook
Evaporation estimates (RS)
Comparison with Flux measurements
Scale effects & boundary conditions of evaporation from SR
Design of reservoirs for optimum storage in dry season?

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Thank you!
www.smallreservoirs.org