managing hydrogeological risks in the lullemeden aquifer system ias (mali, niger, nigeria)
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Managing Hydrogeological Risks in the Iullemeden Aquifer System IAS
(Mali, Niger, Nigeria)
MSP-GEF project
GEF Third Biennial International Waters ConferenceBrazil, 20-25 june, 2005
A. Dodo
Situation of IAS in the Niger river basin
Niger Superior (257 000 km²)
Delta Interior (85.000 Km²)
Niger Middle (660 000 km² ):
Niger Inferior (650 000 km²) :
Niger
Nigeria
Mali
R. Niger
Overview of the Iullemeden Aquifer System
•Mali, Niger, Nigeria•525 000 km²•Mali : 31000 km² (6%)•Niger : 434000 km² (83%)•Nigeria : 60000 km² (11%).
Aquifers:
•Cretaceaous Continental intercalaire
•Tertiary Continental Terminal
The Iullemeden Aquifer System is subjected to several real and/or potential risks :
The increase of the water demand because of the growth of the population : 15 millions in 2000, the double in 2025; A Weak sudden Basin Awareness : groundwater shared; The Climatic changes; The mitigation of groundwater recharge rate (because of deforestation: in
Niger : weak productivity of the forests (0,1 to 1,5 stere/ha/year) against 87% of the energizing needs between 1,5 and 2 millions tons of firewood per year. In Mali: 90% of the needs of firewood) ;
The silting of the rivers (deforestation, erosion); The deterioration of water quality because of: The pollutions: domestic, industrial, mining, artisanal, agricultural; The groundwater geochemistry of the Continental intercalaire (attendance of Apatite): Bony Fluoroseses.
Basin Awareness : Transboundary Shared Water Resources Management
Climatic Changes : Annual isoyietal map (mm) in the Sahel part of the SAI: Sliding of isoyietes southwards of about 100
km: decrease of 20% to 30% of the rainfall
Mitigation of surface run-off : 20 to 50% to the detriment of the Ecosystem
Mitigation of Niger river run-off at Koulikoro: 23 %
Evolution des Modules du Niger à KOULIKORO de 1950 à 2002
0
500
1000
1500
2000
2500
1950
1952
1954
1956
1958
1960
1962
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
Moy.Mobile sur 5 ans
Evolution des Débits annuels : Ecart à la Moyenne
-500-400-300-200-100
0100200300400500600
1950
1954
1958
1962
1966
1970
1974
1978
1982
1986
1990
1994
1998
2002
Ecar
t (m
3/s)
Ecart / Moyenne (864 m3/s)
Mitigation of Niger river run-off at Niamey : 36,2%
Mitigation of Groundwater Recharge rate :Dégradation of land forest for firewood
Erosion and silting in Niger river
Installation of sand dunes
Consequences of deforestation, silting : Subsidence of the groundwater table that sustains very weakly or not the run-
off
-4,00-3,00-2,00-1,00
0,001,00
2,003,004,00
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
-4
-3
-2
-1
0
1
2
3Ecr (Pluie)Ecr (Débit)Cumul Ecr.-Piézo.
(R. Dessouassi et G. Mahé , 1997)
● Niger superior in Mali (Pilot experience in152 500 Km²)
Artisanal Pollution : Tannery, Dyeing
Excess of Fluoride (6 mg/l) in Continental intercalaire Aquifer
More than 300 victims mainly children
irreparably deformed
Bony Fluoroseses Apatite :
Ca5(PO4)3 (OH, F, Cl)
- A state of knowledge of water resources updated in - A state of knowledge of water resources updated in the hole Basin; the hole Basin;
- A Common Data base to the 3 countries; - A Common Data base to the 3 countries;
- A Mathematical Models for the establishment of a - A Mathematical Models for the establishment of a hydrogeological risks map and for sustainable water hydrogeological risks map and for sustainable water resources management; resources management;
- An initiation to the Mechanism of Concertation for the - An initiation to the Mechanism of Concertation for the joint groundwater resources management and for the joint groundwater resources management and for the monitoring of the relevant indicators of monitoring of the relevant indicators of hydrogeological riskshydrogeological risks
MSP-GEF project gives a good opportunities
Thank YouThank You