ESTUDO DA CAPACIDADE DE REGULARIZAÇÃO DE VAZÃO NA BACIA DO RIBEIRÃO SÃO BARTOLOMEU VISANDO ABASTECIMENTO PÚBLICO

O objetivo do presente trabalho foi avaliar a viabilidade de implantação de novos reservatórios de regularização de vazões na bacia do ribeirão São Bartolomeu, Minas Gerais, Brasil. Foram estudadas duas regiões para implementação de novos reservatórios. O cálculo da capacidade máxima de regularização foi realizado com base na metodologia conhecida como diagrama de massas. Para o dimensionamento da estrutura de emergência, foi realizado o cálculo da vazão máxima de projeto a partir do método racional modificado. A vazão média evaporada do período de estudo resultou em 4,5 L s-1 e 1,0 L s-1 para os reservatórios. Foram obtidos volumes úteis de 375.216 m³ e 66.596 m³ e profundidades máximas de 16,2 m e 17,7 m. As áreas dos espelhos de água equivaleram a 93.348 m² e 18.041 m². Tendo em vista o quadro de escassez hídrica no município de Viçosa, recomenda-se a implantação de um dos reservatórios, com aumento da disponibilidade hídrica para fins de abastecimento público. Entretanto, são necessários maiores estudos em relação à potencialidade de aumento dos conflitos por recursos hídricos na bacia. Adicionalmente, ressalta-se a necessidade da avaliação de potenciais alterações na qualidade da água do rio a jusante dos reservatórios propostos.Palavras-chave: disponibilidade hídrica; ponto de captação; reservatórios. STUDY OF FLOW REGULATION CAPACITY IN THE SÃO BARTOLOMEU RIVER BASIN FOR WATER SUPPLY ABSTRACT: This paper aimed to evaluate the viability of the implementation of new reservoirs to regulate flow in the São Bartolomeu river basin, Minas Gerais, Brazil. Two regions were studied. The maximum regularization capacity was calculated based on the methodology known as mass diagram. For the dimensioning of the emergency structure, the maximum design flow was calculated from the modified rational method. The mean evaporated flow of the study period resulted in 4.5 L s-1 and 1.0 L s-1. Useful volumes of 375,216 m³ and 66,596 m³ and maximum depths of 16.2 m and 17.7 m were obtained. The water mirrors areas obtained for the new dams amounted to 93,348 m² and 18,041 m². Considering the situation of water scarcity in the municipality of Viçosa, it is recommended to install one of the proposed reservoirs, with increased availability of water for public supply. However, further studies are needed regarding the potential for increasing conflicts over water resources in the basin. In addition, the need to evaluate changes in river water quality downstream the proposed reservoirs is emphasized.Keywords: water availability; catchment point; reservoirs

Daily rainfall disaggregation for Tocantins State, Brazil

In order to design effective Brazilian hydraulic structures, it is necessary to obtain data relating to short-duration intense rainfall from historical series of daily rainfall. This recurring need can be fulfilled by rainfall disaggregation methodology. The objective of this study was to determine the intense rainfall disaggregation constants for the State of Tocantins and to compare these constants with those obtained for other regions of Brazil. For the modeling of the frequency of intense rainfall of different durations of less than 24 hours, the Gumbel probability distribution (GPD) was employed using rainfall series from 10 locations in Tocantins state. The results showed that the GPD was adequate by the Kolmogorov-Smirnov and Chi-square tests. The disaggregation constants presented low variability values for different return periods (from 10 to 100 years); the values for Tocantins state are: h12h/h24h=0.93, h6h/h24h=0.86, h4h/h24h=0.82, h3h/h24h=0.78, h2h/h24h=0.72, h1h/h24h=0.61, h50min/h1h=0.92, h40min/h1h=0.83, h30min/h1h=0.68, h20min/h30min=0.76 e h10min/h30min=0.46. The comparison of the results with those from studies developed for other Brazilian regions showed variations of up to -62.30%, allowing us to conclude that the use of local constants is important in the process of rainfall disaggregation.Para o dimensionamento da estrutura hidráulicas do Brasil, é necessário a obtenção de dados de chuvas intensas de curta duração a partir de séries históricas de chuva diária. Esta situação recorrente pode ser atendida pela metodologia de desagregação de chuvas. Objetivou-se neste trabalho determinar constantes de desagregação de chuvas intensas para o Estado do Tocantins e proceder a comparação destas constantes com aquelas obtidas para outras regiões do Brasil. Para a modelagem da frequência das chuvas intensas de diferentes durações, foi empregada a distribuição de probabilidades Gumbel, tendo sido utilizadas séries pluviográficas de 10 localidades do estado do Tocantins. Os resultados mostraram que a distribuição de probabilidades Gumbel foi considerada adequada pelos testes Kolmogorov-Smirnov e Qui-quadrado. Observou-se que as constantes de desagregação apresentaram valores praticamente invariáveis para tempos de retorno entre 10 e 100 anos, tendo sido obtidas as seguintes constantes médias para o estado do Tocantins: h12h/h24h=0,93, h6h/h24h=0,86, h4h/h24h=0,82, h3h/h24h=0,78, h2h/h24h=0,72, h1h/h24h=0,61, h50min/h1h=0,92, h40min/h1h=0,83, h30min/h1h=0,68, h20min/h30min=0,76 e h10min/h30min=0,46. A comparação dos resultados com os de estudos desenvolvidos para outras regiões brasileiras mostrou variações de até -62,30%, permitindo se concluir que a utilização de constantes locais é importante no procedimento de desagregação de chuvas

Variable backwater and channel roughness: effects on Solimões River discharge

Historically, streamflow daily values are obtained indirectly by applying a rating curve on water level data. In several Amazon basin stations, a backwater effect impacts the flow, thereby invalidating the rating curve method. To account for this effect, we generated a daily discharge data series by applying the Manning equation to daily water level data from the Manacapuru station located on the Solimões River. Each Manning parameter had to be established based on its relationship to the water level. The roughness coefficient was obtained by inverting the Manning equation for each discharge measurement, and a “coefficient–stage” relationship was established. The slope of the energy line was estimated by the water-surface slope between two fluviometric stations. Discretizing the equations for each parameter enhanced the discharge estimation for the Manacapuru station, thereby generating an accurate discharge data series

Variable backwater and channel roughness: effects on Solimões River discharge

Historically, streamflow daily values are obtained indirectly by applying a rating curve on water level data. In several Amazon basin stations, a backwater effect impacts the flow, thereby invalidating the rating curve method. To account for this effect, we generated a daily discharge data series by applying the Manning equation to daily water level data from the Manacapuru station located on the Solimões River. Each Manning parameter had to be established based on its relationship to the water level. The roughness coefficient was obtained by inverting the Manning equation for each discharge measurement, and a “coefficient–stage” relationship was established. The slope of the energy line was estimated by the water-surface slope between two fluviometric stations. Discretizing the equations for each parameter enhanced the discharge estimation for the Manacapuru station, thereby generating an accurate discharge data series