Analysis of appropriate timescales for water diversion permits in Brazil.

Agreement on the criteria for granting the right to use water resources between governing bodies represents a significant advance in the process of sharing water use. To aid water resource management agencies in optimizing water use, the impact of using different criteria for permitting water use in the Paracatu river basin, Brazil, was evaluated in this study. The streamflow criteria corresponding to 30 % of the annual Q(7,10) (used by the governing body of Minas Gerais), 70 % of the annual Q(95) (used by the governing body of the union), 30 % of the monthly Q(7,10), and 70 % of the monthly Q(95) were evaluated. The use of criteria based on the monthly streamflow allows for better management of water use because it allows for greater utilization of this resource in times when there is high water availability and imposes a more realistic restriction during critical periods. Substitution of the annual Q(7,10) for the monthly Q(7,10) significantly increases the streamflow permitted in some months, for example, from December to May. Use of the criterion of 70 % of the annual Q(95) involves a high risk of drought in critical months, while the criterion of 70 % of the monthly Q(95) minimizes this risk.