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

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2500

1950

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Moy.Mobile sur 5 ans

Evolution des Débits annuels : Ecart à la Moyenne

-500-400-300-200-100

0100200300400500600

1950

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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

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-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