Trade-off assessment in the Senegal River Basin - ICID Amaury Tilmant Jasson Pina - Food and ...
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Trade-off assessment in
the Senegal River Basin
ICID
Saskatoon 2018
Amaury Tilmant
Jasson Pina
1
The Senegal River basin
▪ Located in western Africa
▪ Drainage area = 337000 km2
▪ Shared by four countries: Guinea, Mali, Mauritania and
Senegal
▪ Traditional uses:
• transportation (navigation)
• food production: fisheries + flood recession agriculture
▪ More recently: hydroelectricity
▪ Significant year-to-year variability of river discharges:
• exposes water users to a high hydrological risk
▪ Significant development potential in the basin. Coordination
through the river basin authority: OMVS
2
The Senegal River basin
Artificial flood (AF)
Volume (hm3)
200
180
160
140
120
100
80
60 4.5 km3
40
20
0
By Bourrichon (https://creativecommons.org/licenses/by-sa/3.0)]
3
HEM for the Senegal River basin
▪ As river basins develop it becomes more and more relevant
• To seek efficient allocation policies
• To understand the linkages between
• Economic sectors
• Water users
• Water users and their biophysical and social environment
▪ In the Senegal River basin, the following hydro-economic
principles apply:
• Water should be used where and when its user value is the
greatest
• Water should be stored in reservoirs upstream
• Water for consumptive uses should be withdrawn downstream
▪ How to find the balance between these principles?
Hydro-economic modelling (HEM)
4MAURITANIE
9. Maréla
27 25-26 24 23 22 21 20 19
23. Diama 10. Badoumbé
13. 12.
Océan
Atlantique P N,P N,P N,P N,P N,P
24. 22. 21. 20. 19. 18. 17. 14. 11.
Félou Gouina 8. Boudofora
Lac de Guiers Sénégal
&
Lac Aftout
16. Gourbassi 06
SÉNÉGAL
Légende 7. Bakoye
Zone irriguée et 15. Moussala MALI
Réservoir flux de retour
existant 6. Manantali
Débit
environnemental
Centrale
N Navigation Falémé
hydroélectrique
existante
P Pêche 5. Bindougou
Réservoir (2de
génération)
34.1 Débit naturel annuel [km3]
1.3
Centrale
Pertes annuelles [km3] 4. Boureya
hydroélectrique
(2de génération)
Débits
naturels
Réservoir
(3ème GUINÉE
génération) Diversion 03
Centrale 3.
hydroélectrique
(3ème génération)
2. Koukoutamba
1. Balassa
Bafing
▪ Maximizes expected net benefits from hydropower
generation and irrigated agriculture
• Constraints: M&I uses, artificial flood (eflows), navigation
▪ Up to 10 reservoirs / 12 hydropower plants
▪ 11 irrigation demand nodes / 52 cropsMAURITANIE
9. Maréla
27 25-26 24 23 22 21 20 19
23. Diama 10. Badoumbé
13. 12.
Océan
Atlantique P N,P N,P N,P N,P N,P
24. 22. 21. 20. 19. 18. 17. 14. 11.
Félou Gouina 8. Boudofora
Lac de Guiers Sénégal
&
Lac Aftout
16. Gourbassi 06
SÉNÉGAL
Légende 7. Bakoye
Zone irriguée et 15. Moussala MALI
Réservoir flux de retour
existant 6. Manantali
Débit
environnemental
Centrale
N Navigation Falémé
hydroélectrique
existante
P Pêche 5. Bindougou
Réservoir (2de
génération)
34.1 Débit naturel annuel [km3]
1.3
Centrale
Pertes annuelles [km3] 4. Boureya
hydroélectrique
(2de génération)
Débits
naturels
Réservoir
(3ème GUINÉE
génération) Diversion 03
Centrale 3.
hydroélectrique
(3ème génération)
2. Koukoutamba
1. Balassa
Bafing
▪ Maximizes expected net benefits from hydropower
generation and irrigated agriculture
• Constraints: M&I uses, artificial flood (eflows), navigation
▪ Solved using Stochastic Dual Dynamic Programming (SDDP)
▪ Generic HEM coded in MATLAB + efficient Gurobi solverScenarios - Senegal River basin
▪ Development scenarios represent alternative levels of water
resources’ commitment in the basin
Baseline Mid-development Full-development
2015 2030 2050
2 reservoirs 5 reservoirs 10 reservoirs
2 hpp 6 hpp 12 hpp
74 kha 255 kha 402 kha
5.9 million inhabitants 9.7 million 16.8 million
▪ Management scenarios reflect alternative allocation policies
between competing uses
• Food security: flood recession agriculture, fisheries and irrigation
• …
• Energy security: hydropower generationHydropower generation
▪ Annual energy generation
Baseline Mid-development Full-development
2015 2030 2050
2 reservoirs 5 reservoirs 10 reservoirs
2 hpp 6 hpp 12 hpp
74 kha 255 kha 402 khaCultivated area – flood recession
agriculture
Baseline Mid-development Full-development
2015 2030 2050
2 reservoirs 5 reservoirs 10 reservoirs
2 hpp 6 hpp 12 hpp
74 kha 255 kha 402 khaMarginal value of water
-1800000 -1500000 -1200000 -900000 -600000
2000000
2000000
21 20 M AUR ITA
23
22 ANNIA
1800000
1800000
Diama
19
SE
ENNE
EG A L
18
17
1600000
1600000
14
13
M A L II
12
Félou Legend
Gouina 10 9
ROR
16 8
6 Reservoir
Boudofora
Gourbassi nodes
Manantali
1400000
1400000
River
15
5 Water value
Moussala
Bindougou $/1000m3
4 0.00
GU
U II N
NEEA
0.01 - 0.03
Boureya
2 0.03 - 5
1200000
1200000
5-6
Koukoutamba
1 6 - 19
Balassa 19- 33
-1800000 -1500000 -1200000 -900000 -600000
10Water accounting (2030)
▪ Short-run values and costs (million US$/y)
River basin
services
400
350
Production Storage
Value and cost (million US$/y)
300
Surface and 250
groundwater
Commodity- 200
Hydrologic reservoirs
based
150
Runoff M&I uses
100
Infiltration Hydropower
... Agriculture 50
Navigation
... 0
-50
Guinea Mali Senegal Mauritania
Fisheries 0.4 0.6 3.6 8.4
Irrigation 17.4 3.0 187.7 78.2
Hydropower 199.3 142.9 2.8 0.0
Evaporation -4.7 -5.8 -0.4 0.0
Storage services 57.4 35.6 3.6 0.0
Natural inflows 117.0 29.6 1.1 0.0Indicators
▪ Satisfaction level = degree to which one objective is
achieved in a particular scenario (compared to the max
achievable performance in the corresponding “best”
scenario)
Indicator Scale & units « best » management
scenario
Flood recession ag Flooded area (ha) Food security
Energy Energy (MWh) Energy security
Navigation Probability of exceeding min flow (-) Navigation
Fisheries Fish catch (T) Food security
12Trade-off (2030)
▪ The thick lines = the
average performance of
a particular scenario
▪ Thin lines = performance
for a particular
hydrological year → give
an indication of the year-
to-year variability
13Basin-wide net revenues (2015, 2030,
2050)
Net revenues (million USD)
500
Guinea
450 Mali
Senegal
Mauritania
400
Basin
350
Irrigation and fisheries
300
250
200 Baseline
Energy
150 Food
Full dev. wo flood
Full dev. w flood
100
50
0
0 50 100 150 200 250 300 350 400
Hydropower 14Conclusions and recommendations
▪ Future developments of the basin will exacerbate the
existing trade-offs between competing uses
Hydropower
Hydropower Navigation
Irrigated
agriculture
Flood recession agriculture Flood recession agriculture
Fisheries Fisheries
Ecology Ecology
Baseline Full-development
2015 2050
15Conclusions and recommendations
▪ Future developments of the basin will exacerbate the
existing trade-offs between competing uses
▪ Inter and intra-country trade-offs
Mali,
Guinea,
Mali Mauritania
Senegal
Mauritania
Senegal
Mauritania Mauritania
Senegal Senegal
Baseline Full-development
2015 2050
16Conclusions and recommendations
▪ Food production sector more vulnerable to hydro-climatic
variability
▪ The performance of the Senegal river system can be
significantly improved through the coordinated operation of
the multireservoir system
▪ Impact of climate change on trade-offs has yet to be carried
out
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