Rita de Cássia Fraga Damé

Relações intensidade-duração-frequência obtidas a partir de séries anual e de duração parcial para a localidade de Pelotas-RS

The intensity-duration-frequency occurrence ratio (IDF) is a tool commonly used for precipitation-runoff data transformation, which is established from observations of intense precipitations over a period sufficiently long as to allow the occurrence of extremes at the observation site. This study focused on verifying the existence or absence of new data, in terms of IDF ratio, by using partial duration records produced from data on maximum daily disaggregated rainfall for pre determined durations. The partial duration records considered a base value of 55 mm, totaling 279 values. After the rainfall series were established, their independence and seasonality were assessed. Using the Students t-test statistics, it was established that no new data, as IDF ratio, emerged from the analysis of the partial duration series with the recommended base value of precipitation, as compared to the historical records.

Runoff hydrogram resulting from the methodology employed to record precipitation.

Data of daily precipitation recorded by pluviometers are more easily found than those from pluviographic data. This often constitutes a limitation for hydrological applications such as the rainfall-runoff transformation, which needs to feed on short duration precipitation data. To overcome this constraint, the development of disaggregation models for daily precipitation has been sought for a long time. The aim of this study was to compare different runoff hydrograms resulting from hyetogram estimates from Intensity-Duration-Frequency (IDF) relationship between pluviometric and pluviographic data for the location of Pelotas, RS-Brazil. The relationship method was used to calculate daily precipitation disaggregation, while the runoff depth and its propagation were over a 7 km2 area and were determined through the methodology proposed by SCS (1972). The findings lead to the conclusion that the peak runoff values showed a difference of 12.6, -4.4, 21.8, 38.7, 54.3 and 58.2%, for return periods of 2, 5, 10, 20, 50 and 100 years, respectively, when calculated through the IDF ratio, as compared to the analytical equation.

BARTLETT-LEWIS OF RECTANGULAR PULSE MODIFIED MODEL: ESTIMATE OF PARAMETERS FOR SIMULATION OF PRECIPITATION IN SUB-HOURLY DURATION

The Bartlett-Lewis Rectangular Pulse Modified (BLPRM) model simulates the precipitous slide in the hourly and sub-hourly and has six parameters for each of the twelve months of the year. This study aimed to evaluate the behavior of precipitation series in the duration of 15 min, obtained by simulation using the model BLPRM in situations: (a) where the parameters are estimated from a combination of statistics, creating five different sets; (b) suitability of the model to generate rain. To adjust the parameters were used rain gauge records of Pelotas/RS/Brazil, which statistics were estimated - mean, variance, covariance, autocorrelation coefficient of lag 1, the proportion of dry days in the period considered. The results showed that the parameters related to the time of onset of precipitation (λ) and intensities (μx) were the most stable and the most unstable were ν parameter, related to rain duration. The BLPRM model adequately represented the mean, variance, and proportion of the dry period of the series of precipitation lasting 15 min and, the time dependence of the heights of rain, represented autocorrelation coefficient of the first retardation was statistically less simulated series suitability for the duration of 15 min.

Prediction of rainfall from geographical coordinates of the state of Rio Grande do Sul

Based on the fact that the altitude, latitude and longitude influence climate characteristics of a region, the aim of the present work was to verify the existence of information gain when the statistical procedure of multiple linear regression is applied for the prediction of total precipitates annual, monthly and seasonal, for some municipalities in the state of Rio Grande do Sul were used daily rainfall data from 26 weather stations. Therefore, besides other 7, used for validation of the proposed linear models. Data were obtained from the Agência Nacional de Águas (ANA), which belong to seven mesoregions the state of Rio Grande do Sul. After the formation of the series, precipitation values were adjusted from linear models using linear regression Multiple, in which the dependent variable was the precipitation and the independent variables, the geographic coordinates latitude and longitude, and altitude. The prediction of the values of annual, seasonal and monthly precipitation, depending on the geographical coordinates and altitute, can be performed from the multiple linear regression. Of the three variables, the latitude seems to be that most influences the estimation of precipitation.