Conceptual aspects of the hydrological regime for the definition of environmental hydrograph

Considering the instruments established by the Brazilian National Policy for Water Resources (Law 9,433/1997), the water right concession has the aim to limit water use of surface and groundwater reservoirs. In this sense, the sum of all granted uptake rights must take into consideration the natural ecological flows. It has been a complex challenge to establish a trade off between the management of water and environmental resources since various aspects have to be considered involving many knowledge areas such as ecology and hydrology. This paper focuses on the need for a closer dialogue between these areas by considering the space-time interpretation of the restrictions on natural flow regimes of the water resources. These regimes can be observed in hydrographs, which are indispensable tools for better understanding the hydro-ecologic behavior of rivers