1.1.1.WATER RESOURCES About 47 per cent of the total area of Mali is located in the catchment of the River Niger and 11 per cent in the Senegal River watershed; 41 per cent of the country's area is part of the inner basin of the Sahara Desert; and only 1 per cent is in the catchment of the River Volta. Senegal and Niger’s rivers and their tributaries provide the bulk of perennial surface water flow, an estimated 50km3. The Niger River is one of the largest rivers in Africa with a length of 4,200km, of which 1,700km are in Mali. The volume from the Niger and its tributary the Bani within Mali is around 35km3, of which one-third is lost through evaporation in the central delta and the lake area. The Senegal River is formed mainly by the Bafing, Bakoye and Faleme. The renewable groundwater resources are estimated at 20km3. The common part between surface water and groundwater is estimated at 10km3, giving a total annual renewable water resources of 60km3. About 40km3 of surface water enters the country, mainly from Guinea and Côte d'Ivoire, bringing the total to 100km3 of renewable water resources. The major control structures existing on the Senegal and Niger rivers and their tributaries are: -The dam on the Sankarani Sélingué (tributary of the Niger River), with a capacity of 2.17km3 which can produce energy and support the low flow of the river at a minimum of 75m3/s at Markala; -The dam on the Niger Sotuba which feeds a small hydroelectric plant, and the Baguineda channel for about 30 km3 of irrigation; -The Markala Dam on the Niger, with a capacity of about 0.18km3, which raises the river level and allows the supply channel of the Office du Niger by diversion; -The Manantali Dam on the Bafing, which controls the flow of the Senegal River, with a capacity of about 11.27km3 – and the water thus stored is shared between Senegal, Mauritania and Mali. Wetlands and nature reserves are important in the basins of two rivers, including the central Niger delta (30,000km2). From Segou and particularly in the inner Niger delta, the waves of winter floods give large excesses of water in flood plains, thereby filling the bins of controlled flooding, lakes and ponds for recession crops and pastures, and improving reproduction in fish spawning areas.

1.1.2.WATER USE Current intakes of the irrigation sector are of the order of 5.9km3, or 90 per cent of the total levy, coming from virtually all surface water resources and almost completely over a period of six months (June 1 to December 31). The irrigation of winter crops is generally not a problem given the relatively large flow of rivers during this period. In terms of constraints, we note for groundwater: -The irregularity of rainfall and therefore the flow of rivers, and the annual recharge of groundwater; -Difficulties in locating aquifers in relation to sites of use (the failure rate may reach 30 per cent) and low flow rates (less than 5m3/h for most boreholes); -The cost of drainage and impoundment of surface water (which is very high) and the operating cost of groundwater. Given these factors, to date, an insignificant amount of groundwater resources are used for irrigation. Groundwater is used mainly as a source of drinking water. In 2000, the levy of water for domestic use was estimated at 590 million m3 per year (9 per cent), while industry accounted for about 56 million m3 per year (1 per cent).

1.2.WATER QUALITY, ECOSYSTEMS AND HUMAN HEALTH Major environmental problems are deforestation; soil erosion; desertification; inadequate supplies of potable water; and poaching. Pollution caused by fertilizers and pesticides may in the future acquire a large scale especially in the area of the NAO. Problems of infestation by aquatic plants arise in the upper valley of the River Niger. Wetlands are being degraded due to the lack of a management plan and appropriate conservation measures. Finally, the emergence of schistosomiasis around the reservoirs of dams is the main health problem.