IWRA Proceedings

West Africa has experienced striking fluctuations of precipitation on both recent and historical time scales. In particular, since the early 1970s, several long-term droughts with shorter periods of extreme dryness occurred in the West African Sahel. In interaction with factors caused or influenced by human activities, the significant decrease in rainfall lead to a drastic reduction of the average annual water availability of West African rivers. For the last 30 years, the mean annual water yield of the middle and lower Niger river was reduced by more than 30% if compared with the long term average flow occurring before 1970. In a number of years the Niger river run nearly dry for several weeks along the river stretch of the Republic of Niger, and adversely affected the water use conditions in terms of quantity and quality of the "lifeline" of this country.

In the late 1970s a consortium of consulting engineers under French guidance investigated the Niger river basin development in the Republic of Niger. At that time priority was given to hydropower development rather than water supply. They recommended to build a dam located some 30 km downstream of the border between Mali and Niger, and 190 km upstream of the capital of Niamey. The corresponding reservoir had an enormous useful storage of about 9 billion m3 . Based on economic and other reasons, the project was stopped.

Being aware of the fatal consequences of water shortage, in 1999 the African Development Bank (ADB) financed a feasibility study on river development of the Niger river reach flowing through the Republic of Niger. Aim was to investigate, if the reduced availability of surface water can be substantially improved with the help of a multipurpose dam to be constructed at the same location as planned previously. The new project variant should be designed as small as possible to minimise the investment costs and the environmental impact. For this, extensive environmental and socio-economic analyses were required...