Water Stress Index (WSI) of the Araguaia River Basin, Brazil

Abstract The Araguaia River Basin (ARB), located in Brazil and positioned at the transition between the Cerrado and Amazon biomes, stands out for its socioeconomic, environmental, and cultural importance. The region contains extensive irrigated agricultural areas and numerous communities that depend directly on its water resources. This study evaluated the Water Stress Index (WSI) in the ARB by harmonizing the distinct water-allocation criteria adopted by the different states that comprise the basin, integrating heterogeneous definitions of allowable withdrawal limits and regulatory thresholds into a unified analytical framework. We analyzed data on surface water withdrawal permits, water availability, and WSI values. Irrigation represents 72% of surface water withdrawals and exceeds 94% of total demand in several sub-basins. More than 10 billion m3 of water are withdrawn annually, with the highest concentrations in the Alto Médio Araguaia, Vermelho, Alto Rio das Mortes, and Formoso sub-basins, all classified as areas of highly critical water stress. Near to 25% of the analyzed area already exhibits severe water-stress conditions, a trend that may intensify due to increasing agricultural demand, weak permit-control mechanisms, the effects of climate change, and the lack of harmonized water-management practices among the states.