ABSTRACT Regionalization is an important technique for estimating the flow of hydrographic sections with a lack of data. First, it is necessary to identify hydrologically homogeneous regions (HHRs), which are commonly validated via statistical analyses. Because this step is understood to be subjective, studies that contribute to a greater reliability in identifying regions are needed. In this context, the objective was to evaluate the inclusion of a physical analysis of the average regionalized flow rates as an aid to identify HHRs. The groupings were defined on the basis of geographical convenience methods and cluster analysis. For the assessment of regionalized flows, six statistical indices were used with a physical analysis that was performed via a comparison of the runoff coefficient to the spatial distribution of precipitation values. It was concluded that the physical analysis reduced the subjectivity in the identification of HHRs.

ABSTRACT Knowledge about long-term average flow is essential for planning and managing water resources because it represents the potential water availability. One technique used to determine streamflow is regionalization, but because most gauge stations normally are associated with large drainage areas, the extrapolation of regionalization equations does not accurately represent the water availability; therefore, this method is not recommended. The main objective of the present paper is to propose a new method of estimating water availability that minimizes the risks of extrapolating regionalization equations for long-term average flow. The method is based on the use of a threshold value of the runoff coefficient to obtain the long-term average flow at the positions of the basin where the runoff coefficient estimated by the regionalization equation exceeds the threshold value. It was found that values of the runoff coefficient estimated average flows greater than twice those of the threshold values. The use of this method allows a reliable estimation for long-term average flows in regions of extrapolation without compromising the security of the available water supply.

A consideração da sazonalidade do regime de ocorrência das vazões apresenta um potencial para o aumento da disponibilidade de uso dos recursos hídricos. Visando dar subsídios à otimização do uso da água, neste trabalho avaliou-se o impacto da substituição das vazões de referência anuais pelas mensais no potencial de uso de água ao longo da hidrografia de uma sub-bacia do rio Paracatu. Foi avaliado o impacto tanto na Q7,10 (vazão mínima com sete dias de duração associada a um período de retorno de dez anos) quanto na Q95 (vazão cuja frequência de excedência é de 95%). A utilização das vazões mensais em substituição às anuais tem um alto potencial para a melhoria das condições de uso dos recursos hídricos na bacia analisada. A utilização da vazão Q7,10 mensal em substituição à Q7,10 anual implica em aumentos no potencial de uso que variam de valores de cerca de 10% nos meses de menor disponibilidade até valores que excedem os 200% nos meses de maior abundância dos recursos hídricos de superfície. A utilização da vazão Q95 mensal em substituição à Q95 anual implica em variações do potencial que oscilam de reduções de até 37% nos meses de maior restrição hídrica até valores que excedem os 100% nos meses de maior abundância, logo, seu uso possibilita uma utilização mais racional e segura dos recursos hídricos.

The consideration of the streamflow seasonality has a high potential to improve the water use. In order to give subsidies to the optimization of water use, it was evaluated the impact of the change of reference annual streamflow by the monthly streamflows in the potential water use throughout the hydrography of Paracatu sub-Basin. It was evaluated the impact on Q7,10 (lowest average streamflow during a 7-day period with an average recurrence of 10 years) and on Q95 (permanent flow present 95% of the time). The use of monthly streamflow to substitute the annual streamflow had a high potential of improvement of water resources use in the sub-Basin studied. The use of monthly Q 7,10 in substitution of annual Q 7,10 increases the potential water use that vary from about 10% in the months of lower water availability to values exceeding 200% in the months with higher availability of surface water resources. The use of monthly Q95 in substitution of the annual Q95 implies in changes oscillating from reduction of 37% in months of higher water restriction to values exceeding 100% in the months of higher availability, so the use of monthly Q95 instead of the annual Q95 enables the more rational and safe use of water resources.