trade-off assessment in the senegal river basin...the senegal river basin located in western africa...
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Trade-off assessment in the Senegal River Basin
ICID
Saskatoon 2018
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Amaury Tilmant
Jasson Pina
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
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The Senegal River basin
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By Bourrichon (https://creativecommons.org/licenses/by-sa/3.0)]
020406080
100120140160180200
Volume (hm3)
4.5 km3
Artificial flood (AF)
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greatest• Water should be stored in reservoirs upstream • Water for consumptive uses should be withdrawn downstream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?
4
Hydro-economic modelling (HEM)
Débits naturels
Diversion
Réservoir existant
Centrale hydroélectrique existante
Zone irriguée et flux de retour
Légende
34.1 Débit naturel annuel [km3]
1.3
Pertes annuelles [km3]
1. Balassa
2. Koukoutamba
6. Manantali
15. Moussala
16. Gourbassi
9. Maréla
8. Boudofora
10. Badoumbé
GouinaFélou
Falémé
Bafing
Bakoye
03
06
1920
N,P
23. Diama
Sénégal
2122232427
4. Boureya
5. Bindougou
GUINÉE
MALI
SÉNÉGAL
MAURITANIE
Débit environnemental
N,PN,PN,PN,P
N
P Pêche
Navigation
Lac de Guiers & Lac Aftout
P
OcéanAtlantique
Renforcement de la Gestion des Ressources en Eau Transfrontalières sur le Bassin du Fleuve Sénégal
25-26
3.
7.
3.
11.
12.13.
14.17.18.19.20.21.22.24.
Réservoir (2de génération)
Centrale hydroélectrique(2de génération)
Réservoir (3ème génération)
Centrale hydroélectrique (3ème génération)
▪ 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 crops
Débits naturels
Diversion
Réservoir existant
Centrale hydroélectrique existante
Zone irriguée et flux de retour
Légende
34.1 Débit naturel annuel [km3]
1.3
Pertes annuelles [km3]
1. Balassa
2. Koukoutamba
6. Manantali
15. Moussala
16. Gourbassi
9. Maréla
8. Boudofora
10. Badoumbé
GouinaFélou
Falémé
Bafing
Bakoye
03
06
1920
N,P
23. Diama
Sénégal
2122232427
4. Boureya
5. Bindougou
GUINÉE
MALI
SÉNÉGAL
MAURITANIE
Débit environnemental
N,PN,PN,PN,P
N
P Pêche
Navigation
Lac de Guiers & Lac Aftout
P
OcéanAtlantique
Renforcement de la Gestion des Ressources en Eau Transfrontalières sur le Bassin du Fleuve Sénégal
25-26
3.
7.
3.
11.
12.13.
14.17.18.19.20.21.22.24.
Réservoir (2de génération)
Centrale hydroélectrique(2de génération)
Réservoir (3ème génération)
Centrale hydroélectrique (3ème génération)
▪ 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 solver
Scenarios - Senegal River basin
▪ Development scenarios represent alternative levels of water resources’ commitment in the basin
▪ Management scenarios reflect alternative allocation policies between competing uses
• Food security: flood recession agriculture, fisheries and irrigation
• …
• Energy security: hydropower generation
Baseline2015
2 reservoirs2 hpp74 kha5.9 million inhabitants
Mid-development2030
5 reservoirs6 hpp255 kha9.7 million
Full-development2050
10 reservoirs12 hpp402 kha16.8 million
Hydropower generation
▪ Annual energy generation
Baseline2015
2 reservoirs2 hpp74 kha
Mid-development2030
5 reservoirs6 hpp255 kha
Full-development2050
10 reservoirs12 hpp402 kha
Cultivated area – flood recession agriculture
Baseline2015
2 reservoirs2 hpp74 kha
Mid-development2030
5 reservoirs6 hpp255 kha
Full-development2050
10 reservoirs12 hpp402 kha
Marginal value of water
10
9
86
5
4
2
1
1817
14
16
15
2322 21 20
19
13
12
10
Diama
Félou
Gouina
Boureya
Balassa
Moussala
GourbassiBoudofora
Manantali
Bindougou
Koukoutamba
M A L IM A L I
M A U R I T A N I AM A U R I T A N I A
S E N E G A LS E N E G A L
G U I N E AG U I N E A
-1800000
-1800000
-1500000
-1500000
-1200000
-1200000
-900000
-900000
-600000
-600000
12
00
00
0
12
00
00
0
14
00
00
0
14
00
00
0
16
00
00
0
16
00
00
0
18
00
00
0
18
00
00
0
20
00
00
0
20
00
00
0
Legend
ROR
Reservoir
nodes
River
Water value
$/1000m3
0.00
0.01 - 0.03
0.03 - 5
5 - 6
6 - 19
19- 33
Water accounting (2030)
▪ Short-run values and costs (million US$/y)
River basinservices
Production Storage
HydrologicCommodity-
based
RunoffInfiltration...
M&I usesHydropowerAgricultureNavigation...
Surface and groundwater reservoirs
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 0.0
-50
0
50
100
150
200
250
300
350
400
Val
ue
an
d c
ost
(m
illio
n U
S$/y
)
Indicators
▪ Satisfaction level = degree to which one objective is achieved in a particular scenario (compared to the max achievable performance in the corresponding “best” scenario)
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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
Trade-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
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Basin-wide net revenues (2015, 2030, 2050)
14
0 50 100 150 200 250 300 350 400
Hydropower
0
50
100
150
200
250
300
350
400
450
500
Irri
ga
tio
n a
nd
fis
he
rie
sNet revenues (million USD)
Guinea
Mali
Senegal
Mauritania
Basin
Baseline
Energy
Food
Full dev. wo flood
Full dev. w flood
Conclusions and recommendations
▪ Future developments of the basin will exacerbate the existing trade-offs between competing uses
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Hydropower
Flood recession agricultureFisheriesEcology
HydropowerNavigation
Flood recession agricultureFisheriesEcology
Irrigated agriculture
Baseline2015
Full-development2050
Conclusions and recommendations
▪ Future developments of the basin will exacerbate the existing trade-offs between competing uses
▪ Inter and intra-country trade-offs
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Mali
MauritaniaSenegal
MauritaniaSenegal
MauritaniaSenegal
Mali, Guinea,
MauritaniaSenegal
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Baseline2015
Full-development2050
Conclusions 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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