Intensity-duration-frequency ratios obtained from annual records and partial duration records in the locality of Pelotas - RS, Brazil

Abstract

ABSTRACT: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 Student's 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.KEYWORDS: maximum rainfall, daily disaggregated precipitation, probability models. RELAÇÕES INTENSIDADE-DURAÇÃO-FREQUÊNCIA OBTIDAS A PARTIR DE SÉRIES ANUAL E DE DURAÇÃO PARCIAL PARA A LOCALIDADE DE PELOTAS-RS RESUMO:A relação intensidade-duração-frequência de ocorrência (IDF) é uma ferramenta utilizada nos processos de transformação chuva-vazão, e sua determinação deve ser obtida a partir de observações de chuvas intensas, durante um período de tempo longo e representativo dos eventos extremos do local. O presente trabalho teve como objetivo verificar a existência ou não de ganho de informação, em termos de relação IDF, ao serem utilizadas séries de duração parcial, a partir dos dados de chuva máxima diária desagregada, em durações preestabelecidas. Quanto à série de duração parcial, foi utilizado o valor-base preestabelecido de 55 mm, constituindo então 279 valores. Posteriormente à constituição das séries de chuva, foi avaliada a independência e a estacionaridade dos valores contidos nas mesmas. Pela metodologia do teste "t" de Student, constatou-se que não há ganho de informação em termos de relação IDF quando utilizada a série de duração parcial, com o valor-base preestabelecido de precipitação, comparativamente à série de registros históricos. PALAVRAS-CHAVE: chuva máxima, desagregação de chuva diária, modelos probabilísticos.

Intensity-Duration-Frequency relationships: stochastic modeling and disaggregation of daily rainfall in the lagoa Mirim watershed, Rio Grande do Sul, Brazil

“…The KS statistic values were lower than critical statistics ones were, what means that Gumbel's adjustment was appropriate. Similar statement was achieved by TEIXEIRA et al (2011), who adjusted maximum rainfall intensity values in Pelotas (RS) Brazil; they concluded Gumbel's distribution was adequate since there was adherence between observed and adjusted values that was evidenced by the KS test; thus, there is a consensus on its use for extreme data adjustment.…”

“…Therefore, we may highlight that the values of series of N+M years are somehow similar to the other stations. Furthermore, these values seem to represent more accurately local intense rainfall behaviors whether compared to the series of N years, which is required in estimating the IDF relationships (TEIXEIRA et al, 2011).…”

“…For this purpose, the Gumbel's theoretical probability distribution was used in association with return periods of 5, 10, 20, 50 and 100 years (QUADROS et al, 2011). Then, this annual maximum daily rainfall was disaggregated into periods of 10,20,30,40,50,60,120,360,720 and 1440 min by relation methods (TEIXEIRA et al, 2011).…”

“…Despite its importance, water-flow information are scarce, which complicates the design of hydraulic structures as spillways, drainage canals, as well as those related to soil and water conservation, among others (TEIXEIRA et al, 2011). To get around this situation, hydrological models have been applied for rainfall-runoff transformation (FIORIO et al, 2012;LALOZAEE et al, 2013).…”

Climate trends in the municipality of Pelotas, state of Rio Grande do Sul, Brazil

“…As already described in other studies like Wilks (2011) and Teixeira et al (2011), the KSL test is more suitable for assessing the central part of the distributions. In relation to the extreme values statistics, the AD test relies on the sum of squares of differences between theoretical and empirical distributions and on a weight function [Ψ(.…”