Prospective scenarios for water sustainability in the São Francisco River Basin

Expanding water demands and increasing uncertainties associate with water availability in the context of climate change are drivers of future development scenarios in water management of river basins. Water limitations can be particularly important in developing countries, where agriculture and livestock constitute the basis of the economy. Although many researchers have dealt with quantification of water, the application of methods to evaluate the relationship between demand and availability is still scarce in the literature. In the present research, water demand prospective scenarios for the São Francisco River Basin, Brazil were developed, allowing the determination of management procedures to spare this resource. Starting from the present situation, three distinct future evolution scenarios were drawn for water withdrawal flows for the years 2025 and 2035 based on sub-basin water use sectors (farming, industry, human supply—urban and rural, and water diversion for external use): a tendential scenario (B) drawn from the present water uses; a moderate water consumption scenario (A), associated with smaller economic and social development; and a stronger development scenario (C), with increases in water demand. Sustainability of water demand is assessed by comparing water availability, as the ratio between the water demand and observed flows. Regardless of the complexity and extent of the region, applied geographic information system was able to depict the water availability and determine management procedures. The main water withdrawal is associated with irrigated agriculture. For the three prospective scenarios, it is expected that the situation tends to get worse, leading to severe water scarcity in most sub-basins and posing several challenges for the water resources management. Management actions are proposed, in order to equilibrate the water availability in the basin.