Evaluation of the new maximum water authorized in Rio de Janeiro state / Avaliação da nova vazão máxima outorgável do estado do Rio de Janeiro

A water rights permit is an important instrument of the Brazilian National Water Resources Policy and aims to ensure the quantitative and qualitative control of watercourses, guaranteeing the maintenance of multiple uses and the right of access to water. Most Brazilian water resource management agencies adopt, in the evaluation of water availability, the maximum water authorized, represented by percentages of the Q7,10 and Q95% reference flows. The State Institute of the Environment, the governing body of the water resources in the state of Rio de Janeiro, calculated water availability based on the maximum water authorized of 50% of Q7,10, and since 2019, 40% of Q95% has been adopted. Considering the difference between the values, we evaluated the magnitude and impact of the current maximum water authorized in granting processes for water use in Rio de Janeiro state, which is inserted almost entirely in subbasin 59. Based on the results, it is recommended to adopt a more conservative criterion represented by 30% of Q95%, estimated at the monthly level.