Assessing water resources in large river basins is crucial for managing water effectively. A review of 40 articles on water assessment in Madagascar's major river basins suggests using multiple GCMs and SWAT models to allocate water properly between upper and lower reaches. By combining these models with inter- and intra-basin approaches, water scarcity issues can be addressed at the basin level. This approach could help scientists and water specialists assess water resources more efficiently on a large scale.