RESUMONos últimos anos, a variabilidade climática e o uso desordenado do solo têm impactado vários componentes do ciclo hidrológico em muitas regiões em todo o mundo, fazendo com que as séries hidrológicas deixem de ser estacionárias. Este trabalho tem por finalidade identificar se as vazões máximas anuais diárias da bacia hidrográfica do Rio Pardo apresentam comportamento não estacionário e o principal motivo de tal fator. Os dados pluviométricos e fluviométricos de vazão foram obtidos a partir do banco de dados históricos disponibilizados pela Agência Nacional de Águas (ANA), entre os anos de 1941 a 2013. Os dados de uso do solo, para caracterização da área antropizada são provenientes do Grupo de Pesquisa em Interação Atmosfera-Biosfera da UFV, onde foram utilizados apenas os dados de pastagens plantadas como classificação do uso do solo de 1940 a 2010. Os testes estatísticos empregados para a identificação da não estacionariedade foram os testes não paramétricos de Mann-Kendall e Spearman Rho, além do teste de Pettitt para localizar o ponto de ruptura na série. Foi identificada uma tendência crescente na série de vazão anual máxima diária do Rio Pardo, logo, esta não se caracterizou como estacionária. Como os eventos de precipitação estão estatisticamente estacionários, a substituição da vegetação natural por pastagens plantadas, representa um dos principais fatores do comportamento da série de vazão máxima não ser mais estacionária. PALAVRAS-CHAVE:Hidrologia, Uso do solo, Teste de tendência, Ponto de mudança. STATISTICAL ANALYSIS OF NON-STATIONARY TIME SERIES OF ANNUAL MAXIMUM DAILY FLOW IN THE PARDO RIVER BASIN ABSTRACTIn recent years, climate variability and disorderly land use have impacted in various components of the hydrological cycle in many regions around the world, making the hydrologic series stop to be stationary. This study aims to identify if the annual maximum daily flow in the Pardo River Basin showing non-stationary behavior and the main reason for this factor. The rainfall and streamflow data of flow were obtained from the historical database provided by the National Water Agency (ANA), between the years 1941-2013. The land use data utilized to characterize the anthropic area are from the Research Group in Atmosphere-Biosphere Interaction of Federal University of Viçosa, which were used only the pastures planted data as classification of land use from 1940 until 2010. The statistical tests utilized for identification of non-stationarity were the non-parametric tests of Mann-Kendall and Spearman's Rho, besides Pettitt test to locate the break point in the serie. It was identified an increasing trend in the series of the annual maximum daily flow in the Pardo River Basin, so it was not characterized as stationary. As precipitation events are statistically stationary, the replacement of natural vegetation by planted pastures represents one of the main factors of the maximum flow serie not be considered as stationary.
RESUMOA bacia hidrográfica do rio Solimões tem sua recarga hídrica modulada por diversos sistemas atmosféricos, onde a porção norte sofre maior influência da Zona de Convergência Intertropical (ZCIT) e a porção sul tem influência da Zona de Convergência do Atlântico Sul (ZCAS), bem como aglomerados convectivos e sistemas frontais atuantes nessa região. Contudo eventos de El Niño e Dipolo do Atlântico podem modular o regime pluvial causando estiagens severas. O objetivo deste estudo foi analisar o comportamento pluviométrico na bacia hidrográfica do rio Solimões nos anos de 2005 e 2010, marcados como as maiores secas do século na Amazônia. Os resultados obtidos mostraram que a pluviometria na bacia do rio Solimões foi drasticamente reduzida na região sudoeste em 2005. Já em 2010 toda a porção oeste e sul da bacia foram afetadas durante a seca. Este comportamento está vinculado ocorrência dos fenômenos ENOS fase positiva e do dipolo do Atlântico positivo, que são fortes moduladores da precipitação na Amazônia. Logo, observa-se que o rio Solimões tem sofrido com os fenômenos climáticos que atuam na Região Amazônica, com consequente repercussão nas cidades que se localizam as suas margens. Palavras-chave: Seca; Amazônia; Solimões; El Niño; Dipolo do Atlântico. ABSTRACTThe basin of the Solimões river has its water recharge modulated by various weather systems, where the northern part suffers greater influence of Intertropical Convergence Zone (ITCZ) and the southern portion influences the convergence zone of the (SACZ) south Atlantic and convective clusters and frontal systems operating in this region. However events of El Nino and the Atlantic Dipole can modulate the rainfalls causing severe droughts. The objective of this study was to analyze the rainfall behavior in the basin of the Solimões River in 2005 and 2010, marked the worst droughts of the century in Amazônia. The results showed that the rainfall in the Solimões basin has been drastically reduced in the southwest region in 2005. In 2010 the entire western and southern portion of the basin were affected during drought. This behavior is linked occurrence of ENSO phenomena positive phase and the positive dipole Atlantic, which are strong modulators of precipitation in the Amazon. Therefore, it is observed that the Solimões river has suffered from the weather phenomena that operate in the Amazon region, with consequent impact on the cities that are located on its banks.
Satellite precipitation estimates are used as an alternative or as a supplement to the records of the in situ stations. Although some satellite precipitation products have reasonably consistent time series, they are often limited to specific geographic areas. The main objective of this study was to evaluate CHIRPS version 2, MSWEP version 2, and PERSIANN-CDR, compared to gridBR, as daily mean and extreme inputs represented on a monthly scale and their respective seasonal trends of rainfall in the Mearim River Drainage Basin (MDB), Maranhão state, Brazil. Estimates of errors were calculated (relative error, pbias; root mean square error, RMSE, and Willmott concordance index, d), and the chances of precipitation were estimated by remote sensing (RES). In addition, trends in precipitation were estimated by the two-sample Mann–Kendall test. Given the overall performance, the best products for estimating monthly mean daily rainfall in the MDB are CHIRPS and PERSIANN-CDR, especially for rainy months (December to May). For daily extremes on the monthly scale, the best RES is PERSIANN-CDR. There is no general agreement between gridBR and RES methods for the trend signal, even a nonsignificant one, much less a significant one. The use of MSWEP for the MDB region is discouraged by this study because it overestimates monthly averages and extremes. Finally, studies of this kind in drainage basins are essential to improve the information generated for managing territories and developing regionalized climate and hydrological models.
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