Na gestão dos recursos hídricos se deve buscar a harmonização entre as demandas dos usos múltiplos da água e a disponibilidade hídrica, entendendo-se esta como o quantitativo a ser utilizado de forma ambientalmente sustentável. Distribuições de probabilidade de vazões são ferramentas essenciais para avaliar a disponibilidade hídrica. Os objetivos deste trabalho foram analisar qual a melhor distribuição de probabilidade que se ajusta aos dados mínimos anuais de vazão diária média em períodos consecutivos de sete dias (Q7) de 14 estações fluviométricas da Bacia do Rio das Velhas e identificar possíveis tendências nas séries de Q7 e em conjuntos bimestrais e anuais de vazões diárias em três relevantes estações. O ajuste das distribuições foi verificado pelo teste de Anderson-Darling (A-D). A seleção dos modelos que apresentaram melhor ajuste foi feita segundo o Critério de Informação Bayesiano (BIC). Para analisar a tendência das vazões, foi utilizado o teste estatístico Mann-Kendall. As distribuições que em geral melhor se ajustaram aos dados e ocuparam a melhor posição no ranking foram Gumbel e Rayleigh. Constataram-se tendências negativas nas três estações. Para a estação de Várzea da Palma, a mais próxima da foz do rio, foram encontradas tendências negativas e significativas para os dados do Q7 e vazão média diária para todos os bimestres, exceto o primeiro.
Palavras-chave: Mann-Kendall, recursos hídricos, seleção de modelos.
In the management of water resources, it is necessary to balance the demands of multiple uses of water and water availability, while enabling use in an environmentally sustainable way. Probability distributions of flow rates are essential tools for assessing water availability. The objectives of this work were to analyze the best probability distribution that conforms to the annual minimum daily average discharge for periods of seven consecutive days (Q7) for 14 stream gauging stations in the Das Velhas River Basin and to identify possible trends in Q7 time series and in bi monthly and annual sets of daily discharges in three key stream gauging stations. The quality of fit was verified by the Anderson-Darling test (A-D). The selection of the models that presented the best fit was done according to the Bayesian Information Criterion (BIC). The Mann-Kendall test was used to verify trends in time series of discharge. In general, better measures of quality of fit were obtained for the probability distributions Gumbel and Rayleigh. Negative trends in discharge distributions were verified in the three stations. For the Várzea da Palma station, the closest to the river mouth, negative and significant trends were found for the Q7 data and daily average discharge for every bimester except the first.
In the management of water resources, it is necessary to balance the demands of multiple uses of water and water availability, while enabling use in an environmentally sustainable way. Probability distributions of flow rates are essential tools for assessing water availability. The objectives of this work were to analyze the best probability distribution that conforms to the annual minimum daily average discharge for periods of seven consecutive days (Q7) for 14 stream gauging stations in the Das Velhas River Basin and to identify possible trends in Q7 time series and in bi monthly and annual sets of daily discharges in three key stream gauging stations. The quality of fit was verified by the Anderson-Darling test (A-D). The selection of the models that presented the best fit was done according to the Bayesian Information Criterion (BIC). The Mann-Kendall test was used to verify trends in time series of discharge. In general, better measures of quality of fit were obtained for the probability distributions Gumbel and Rayleigh. Negative trends in discharge distributions were verified in the three stations. For the Várzea da Palma station, the closest to the river mouth, negative and significant trends were found for the Q7 data and daily average discharge for every bimester except the first.
