Study regionThe study was conducted in the Rio Grande do Sul state – Brazil.Study focusStudies about heavy rainfall events are crucial for proper flood management in river basins and for the design of hydraulic infrastructure. In Brazil, the lack of runoff monitoring is evident, therefore, designers commonly use rainfall intensity–duration–frequency (IDF) relationships to derive streamflow-related information. In order to aid the adjustment of IDF relationships, the probabilistic modeling of extreme rainfall is often employed. The objective of this study was to evaluate whether the GEV and Kappa multiparameter probability distributions have more satisfying performance than traditional two-parameter distributions such as Gumbel and Log-Normal in the modeling of extreme rainfall events in southern Brazil. Such distributions were adjusted by the L-moments method and the goodness-of-fit was verified by the Kolmogorov–Smirnov, Chi-Square, Filliben and Anderson–Darling tests.New hydrological insights for the regionThe Anderson–Darling and Filliben tests were the most restrictive in this study. Based on the Anderson–Darling test, it was found that the Kappa distribution presented the best performance, followed by the GEV. This finding provides evidence that these multiparameter distributions result, for the region of study, in greater accuracy for the generation of intensity–duration–frequency curves and the prediction of peak streamflows and design hydrographs. As a result, this finding can support the design of hydraulic structures and flood management in river basins

A gestão de cheias em bacias hidrográficas brasileiras deve ser discutida e priorizada, porém o cenário atual indica lacunas quanto às informações hidrológicas com variabilidade espacial e temporal condizentes. A modelagem probabilística de eventos extremos de precipitação, buscando a extrapolação para uma frequência e duração, pode servir como excelente ferramenta de análise e tomada de decisões. O objetivo principal deste trabalho foi analisar o ajuste de diferentes modelos probabilísticos a séries de precipitação máxima diária anual no Rio Grande do Sul. Séries pluviométricas de 342 estações foram ajustadas às distribuições Log-Normal a 2 e 3 parâmetros e Gumbel e a adequação foi realizada pelos testes de Kolmogorov-Smirnov e Qui-Quadrado. Todas as distribuições de probabilidade consideradas foram adequadas; entretanto, a distribuição Log-Normal a 3 parâmetros apresentou os melhores ajustes segundo os resultados do teste Qui-Quadrado. Os parâmetros das distribuições de probabilidades apresentaram variabilidade ao longo do estado e forte relação com a localização, sugerindo que a regionalização de chuvas intensas pode ser empregada no Rio Grande do Sul como excelente ferramenta de gestão.

Land leveling is used to correct soil surface irregularities to improve surface drainage and irrigation. It also makes the area more manageable for an array of agricultural activities such as planting and harvesting. The objective of this work was to evaluate two designs of land forming, one aimed at optimizing drainage and the other at optimizing surface irrigation, using fields with reliefs typical of the lowlands of southern Brazil. Seven commercial rice fields, ranging in size from 7 to 26 ha, were randomly selected and digital elevation designs generated for each. Land-leveling projects were developed using three designs: uniform slope (US) (control), land forming–drainage (LFD), and land forming–irrigation (LFI). Performance comparisons between the designs were evaluated through impacts on soil movement (SM), maximum cut in 99% of the area (MC), cumulative length of levees (LL), and total number of levees (NL). Results indicate that both LFD and LFI designs would reduce costs and require less soil disturbance compared to leveling to uniform slopes. LFD would require less soil movement and lower maximum cuts than LFI. However, LFI would reduce the lengths and numbers of rice levees that could have long-term economic and agronomic benefits not captured in these analyses. These results demonstrate that all land-leveling and land-forming alternatives should be thoroughly examined before undertaking field operations. Study outcomes will be useful to engineers and producers in evaluating options to improve the agricultural productivity of lowlands in southern Brazil, a region of national and international significance.

A uniformidade de aplicação de água é um importante fator a ser considerado na avaliação dos sistemas de irrigação por aspersão. A uniformidade em sistemas convencionais de aspersão depende de fatores como: o tipo de aspersor e suas condições operacionais, a disposição e o espaçamento entre aspersores no campo, e a velocidade e a direção do vento durante o período de aplicação de água. Tendo em visa que as complexas relações entre esses fatores e a uniformidade podem ser caracterizadas de forma mais eficiente com o auxílio da modelagem matemática, neste estudo, foram avaliadas simulações, fornecidas pelo modelo semiempírico de RICHARDS & WEATHERHEAD (1993), da distribuição espacial da água aplicada pelo canhão PLONA-RL250, operando sob diferentes condições de vento. Valores de uniformidade de Christiansen (CUC), obtidos com dados de ensaios de campo e em simulações digitais, foram comparados, mostrando-se, por meio de diversos índices (R² = 0,73; desvio absoluto médio de 4,1% e índice de desempenho de 0,78), que o modelo semiempírico avaliado fornece estimativas adequadas do CUC de sistemas convencionais de irrigação. Demonstra-se que a modelagem matemática permite reduzir o esforço e o tempo requeridos em trabalhos de campo envolvendo a avaliação da distribuição de água de canhões hidráulicos operando sob condições de vento.

Investigations demonstrate that the wind is the factor that causes the biggest negative influence on water application of sprinkler irrigation systems. Therefore, this paper aims to evaluate, in in-field conditions, the influence of wind on the water distribution uniformity of a mechanical lateral move sprinkler system used for irrigation in rice crop in the South of Rio Grande do Sul State, Brazil. The equipment is located at the Campo Experimental de Terras Baixas (ETB) of EMBRAPA/CPACT and operates with water emitters model I-Wob installed in drop tubes in a distance of 2.8m above the soil surface, having a uniform space of 2.3m between each other and pressure regulators of 68.9kPa. Sixteen in-field evaluations were done and they permitted to infer that the higher is the wind speed, the lower are the values of Christiansen Uniformity (CU) and of Distribution Uniformity (DU) coefficients. Besides, it can be affirmed that even in unfavorable wind conditions, the mechanical lateral move irrigation equipment presented desirable indexes of water application uniformity.