Índice de variabilidade do escoamento nas escalas semanal e mensal: Estação Fluviométrica Engenho Mato Grosso/PE.

Abstract

The granting of rights is one of the main water management instruments in Brazil. Proposing criteria for the granting of water resources is a complex task, since it is necessary to consider the different types of users, as well as the ecological and quantitative demand that is fundamental for the maintenance of the aquatic environment. The use of reference flow, as a fixed value applied for the whole hydrological year, has been one of the criteria most used in the grant models. However, part of the contributions exceeding this limit, especially during rainy periods, could be considered. The present work refers to the delimitation of the rise and recession of the flow and calculation of indices denoting the proportion of this variability in relation to the fluvial flow. Data were used from the Engenho Mato Grosso fluviometric station, located in the Sirinhaém watershed, in the municipality of Rio Formoso/PE/Brazil. Flows were considered in the monthly and weekly scales. Contributions were calculated in the monthly and weekly scales flow. The results indicated that the variability in the monthly scale was more significant in the rainy months than in the dry season. In the weekly scale, the indices presented in a heterogeneous way throughout the year, especially in 1999, 2000, 2002 and 2004. The results emphasize the importance of addressing flow variability, supporting the creation of the environmental hydrograph, subsidizing decisions on grant allocation, leaving the traditional use of minimum/single value throughout the hydrological year, for an approach which flexibilizes values according to flow regime.