The desertification of Sahel region along the southern Sahara desert result in the most serious environmental problems in west Africa. One of the proposed countermeasures against the desertification is afforestation in this area.
We, authers, set up the anti-desertification project in this region, utilizing undeveloped subsurface water resources and solar energy which are used for the irrigation of tree-plantation and agriculture.
Two years research and field survey on the underground water involved in the fossil valley of the Sahel region clarified the feasibility of construction of subsurface dam.
In this paper, some characteristics of the water resources and of the proposed afforestation project in this region are summerized in view point of utilization of water. Hydrological characteristics of fossil valley are also described in relating with the construction of underground dam.
The fossil valley distributing in the Sahel region cut the basement rocks downward and are filled with sand and grabel which are most suitable container for the storage ofsubsurface water. This type of water which is not developed for the present is supplied by rain fall in the corresponding area.
Subsurface water stored in the fill materials of the fossil valley can be supplied enough in the dry season for the plantation, even if it is in the draught continuing a few years.
The subsurface water storage system described in this paper is the most effective method for utilizing water in the Sahel region where the evaporation rate exceed some thousand millimeter a year.
