Abstract: The Lake Chad basin is one of the regions in Africa with the most prominent water conflicts, and the water crisis has seriously constrained economic development and social stability, and also affected the relations among countries in the basin. This paper carries out literature search and collation from the shrinkage of Lake Chad, the reduction of river runoff, the shrinkage of wetlands, groundwater and water conflicts, etc., comprehensively summarizes the evolution of the water crisis in the Lake Chad basin, and systematically summarizes the causes of the water crisis in the basin. The following conclusions are drawn from the literature analysis: 1) The water crisis in Lake Chad is mainly manifested at the natural level by the drastic shrinkage of the surface of Lake Chad since the 1960s, the drastic decline of the runoff of rivers, the degradation of wetlands, the depletion of groundwater resources in many regions, the frequent occurrence of water disputes and conflicts, the deterioration of the conditions for economic and social development, and the rapid spread of the accompanying terrorist organizations. 2) The multi-decadal drought from the 1960s to the 1980s was a major cause of the shrinkage of river runoff and lakes in the Lake Chad basin, and at the same time prompted a surge in the construction of water conservation projects in the region. The cluster of water conservancy projects, mainly dam projects, not only reduced the river runoff volume, but also changed the seasonal distribution of river runoff, aggravated the degradation of wetlands, and reduced the amount of groundwater recharge in the coastal areas, thus further exacerbating the water resources crisis. 3) The rapid increase in water demand brought about by rapid population growth has further intensified the contradiction between supply and demand of water resources in the Lake Chad basin, while the lack of a unified and effective mechanism for coordinated cooperation in the basin has impeded the improvement of the level of water resources management in the basin, thus limiting the improvement of the overall capacity of the countries in the basin to cope with the water crisis. In conclusion, the water crisis in the Lake Chad basin is still a hot issue in the international community.Analyzing and solving the problem from multiple perspectives will be an important direction for the development of the water crisis in the Lake Chad basin.

Key words: Lake Chad basin, Lake Chad shrinkage, declining groundwater levels, water conflict, water resource management