The proper design of hydraulic structures depends on estimates of maximum stream flows. The scarce stream flow monitoring in Brazil has led to the use of regionalization methods. The main objective of this study was to develop a tool via regional function to estimate maximum stream flows and their corresponding return periods (RP) with the aid of techniques based on the L-moments method, seeking for adequate hydrologic engineering applications and flood risk management. Annual maximum stream flow historical series were adjusted to traditional 2-parameter probability density functions (PDFs) (Normal, 2-parameter Log-Normal, Gumbel, Gamma) and multiparameter PDFs (GEV and Kappa), based on the L-moments method, which were used in the development of the regional function employing the dimensionless curve method. The regional function’s predictive capability was determined by cross-validation for different RPs. It can be concluded that the approach based on L-moments was successfully used to adjust the regional function. In addition, the regional function: i) was improved when using the aforementioned multiparameter PDFs and ii) was framed as optimum for RP of up to 100 years and considered useful for practical engineering projects and flood risk management.

Watershed hydrology is greatly dependent on the analysis of intense rainfall, especially when management and conservation of soil and water, flood management and hydraulic designs are necessary. The intense rainfall modeling should preferably use pluviographic data; however, this type of record is more infrequent than daily rainfall. As a result, methodologies of daily rainfall disaggregation have been commonly adopted to adjust intensity-duration-frequency (IDF) curves. This study had as main objective to evaluate the influence of three sets of disaggregation constants on the estimation of rainfall intensities using IDF curves adjusted from daily rainfall series in the state of Rio Grande do Sul. Based on the substantial variation of the coefficients for the 15 municipalities evaluated in this study, it can be stated that the disaggregation constants exerted influence on the adjustment of the IDF curves. Considering the statistical measure applied in this study, the best adjustment was obtained for the disaggregation constants proposed by CETESB. In order to make it available more realistic results in Rio Grande do Sul State for the decision-making in the scope of water resources, it is advisable to: i) use longer and more recent pluviographic data series for the state; ii) evaluate multiparameter probability distributions; and iii) determine regional disaggregation constants. RESUMO: Quando são necessários o manejo e conservação de solo e água, a gestão de cheias e dimensionamentos hidráulicos, a hidrologia de bacias hidrográficas é enormemente dependente da análise de chuvas intensas. A modelagem de chuvas intensas deve preferencialmente empregar dados pluviográficos; entretanto, este tipo de informação é mais incomum do que dados pluviométricos (chuva diária). Assim, metodologias de desagregaçãode chuva diária têm sido comumente empregadas a fim de ajustar curvas intensidade-duração-frequência (IDF). Este estudo teve como objetivo principal avaliar a influência de três conjuntos de constantes de desagregação na estimativa de intensidades de chuva usando curvas IDF ajustadas a partir de séries de chuva diária no estado do Rio Grande do Sul. A variação substancial dos coeficientes obtidos para os 15 municípios avaliados neste estudo permite afirmar que as constantes de desagregação exerceram influência no ajuste das curvas IDF. Considerando a medida estatística aplicada neste estudo, constatou-se que o melhor ajuste foi obtido para as constantes de desagregação propostas pela CETESB. No intuito de disponibilizar resultados mais realísticos no estado do Rio Grande do Sul para a tomada de decisões, no contexto de recursos hídricos, é plausível: i) usar séries de dados pluviográficos mais longas e recentes para o estado; ii) avaliar distribuições de probabilidades multi-parâmetros ; iii) determinar constantes regionais de desagregação.

Acquisition and analysis of hydrological series are essential activities for hydrological studies in watersheds. However, they require time and are usually complex and susceptible to human errors. In order to minimize these problems, computational tools are often used for hydrological analysis, although there are few of them in Brazil. This technical note aims to provide a structured document with information on the motivation, development, conception, main functionalities, and applications of the System of Hydrological Data Acquisition and Analysis (SYHDA). SYHDA is a software intended for acquisition and analysis of hydrological data (rainfall and streamflow) and was fully idealized to enable the user to deal with the country’s leading hydrology databases. It has several modules that include analysis by descriptive statistics and graphical tools, seasonality analysis of streamflows, non-parametric tests, and at-site and regional probabilistic modeling. SYHDA has been used in numerous scientific studies, which give grounds to affirm that it demonstrates a great potential to be used in both everyday and complex activities demanded by the scientific and technical community of hydrology and related areas.