The São Francisco river crosses some of the driest parts of the Brazilian Semi-arid Region and brings life to ecosystems and to millions of people. Droughts are a recurrent problem in the basin. Since the second part of the twentieth century, several dams, irrigation projects, and water and sanitation systems have been built, and these developments have impacted river conditions, such as stream flows, sedimentation, silting, and water quality. The development of the river, and its engineering solutions, have prioritized the hydroelectric and agricultural sectors. This has started to change with the new water law of 1997 and the creation of the National Water Agency (ANA) in 2000. This chapter reviews current water management and use in the basin as well as the scenarios, which indicate that, in the future, precipitation and stream flows may be reduced significantly due to climate change while water demand will increase due to population growth and development.

Inter-basin water transfers (IBWT) offer an approach to addressing water scarcity by confronting the mismatch between water supply and demand in the context of a sustainable development policy. However, IBWTs are often criticized – particularly when the water transfer involves crossing political boundaries. In those circumstances, the policy debate often tends to lose sight of important aspects that guarantee a rational water policy. This chapter addresses issues related to water transfers between river basins, not only in the hydrological term but also, quite frequently, over political boundaries (transboundary water transfer). We present a number of case studies chosen to provide a representative geographical view of IBWTs around the world and insights on the different aspects that involve IBWTs. Intelligent IBWT should be implemented in the context of more general sustainable development strategies and Integrated Water Resources Management.