Water scarcity under scenarios for global climate change and regional development in semiarid Northeastern Brazil

The State of Ceará, located in semiarid Northeastern Brazil, suffers under irregularly recurring droughts that go along with water scarcity. Structural policies to control and reduce water scarcity, as water supply and demand management, should be seen as long-term planning, and thus have to consider climate change and regional development. To this end, the present research proposes a model-based global change scenario. Water stress is assessed for 184 municipalities in Ceará between 2001 and 2025. For this purpose, four global change scenarios are developed, considering both global climate change and the effects of development policies. Climatic, hydrological and water use models are applied and a proposed index computed for identification of long-term water stress. Application of the methodology in the focus area shows that, if no effective intervention measures are taken, up to almost 60% of the municipalities of the State may suffer under long-term water scarcity by 2025. On average, municipalities in the state of Ceará have a water shortage probability for the next 25 years ranging from 9%yr-1 to 20%yr-1, depending on the scenario. The 10% most stressed municipalities have a probability of over 80%yr-1 of facing water scarcity in the scenario period (25 years). Results also show that a decentralized development policy can compensate for the possible severe effects of climatic trends on future water availability over the scenario period