Flow is one of the hydrological variables of greatest interest due to its connection with water availability and its multiple uses. However, in recent years this resource has been threatened by intense land use and climate change, affecting patterns previously considered to be stationary. The goal of this study was to evaluate trends in changes of patterns of flow, precipitation, and land use in a basin located in the Brazilian Cerrado. 33 years of rainfall, fluviometric, and land use data were used, covering the period of 1985 to 2018 on an annual scale. Mann-Kendall and Sen Slope’s nonparametric test was applied to evaluate the trends in temporal series, as well as the Spearman Rho and Pettit, which were used to analyze the correlations between variables and detect the point of change in the series, respectively. The results show statistically significant trends in flow reduction over time. At the same time, a considerable reduction in natural areas occurred, with an increase of +750% in agricultural areas. The results also show that although a tendency to reduce precipitation was detected, its magnitude was not significant, with land use changes being the main factor for the negative changes in the flow of the Rio Grande tributary.
Hydrological modeling presents itself as a fundamental tool for the management and management of water resources, since it helps to understand the flow of water, sediments and contaminants in a hydrographic basin. The Correntina River basin, located in the western region of Bahia, has been undergoing an intense process of alteration in its landscape motivated by the expansion of agricultural areas in the region, requiring the adoption of instruments for studies that assess the environmental impacts mainly on surface water resources. Thus, the present study aimed to evaluate the effectiveness of the SWAT model for representing the hydrological behavior in the hydrographic basin of the Correntina River, using the SWAT-CUP for automatic calibration and validation. Statistical performance coefficients attested the model's capacity for hydrological simulations in this basin on a monthly time scale, with KGE, Pbias, NSE and R² showing values ​​of 0.69, 0.57, 0.5% and 0.74 in the calibration stage, and 0.73, -3.95 %, 0.64 and 0.76 in the validation step, respectively. In addition, the SWAT was also shown to be suitable for simulating the permanence curves, characterizing the model as a good tool to aid the management of water resources in the basin under study. Subsequent studies will make it possible to analyze the impacts of land use and climate change on the hydrological behavior of the basin under study.
A bacia hidrográfica do Rio Água Branca que assim como outras bacias tem sofrido alterações de origem antrópica, como desmatamento de matas ciliares, poluição dos rios e modificações na paisagem. Estes impactos podem variar de acordo com o uso e cobertura do solo e podem ser mitigados ou melhor ordenados com o uso do geoprocessamento. Neste sentido, a presente pesquisa objetivou mapear a cobertura do solo na bacia, utilizando imagens disponibilizadas gratuitamente pelo software TerraIcognita referentes ao ano de 2018 e processadas em ambiente SIG. Utilizou-se neste trabalho a classificação supervisionada das imagens, que possibilitou analisar a condição dos fragmentos florestais através das métricas da paisagem, esta metodologia também tornou possível a delimitação das áreas de preservação permanente juntamente a legislação vigente. Os métodos usados permitiram chegar nos seguintes resultados: caracterização da cobertura da bacia hidrográfica, onde a vegetação está disposta a paisagem como fragmentos, totalizando 8 fragmentos, variando entre 214 ha e 75 ha, que sob o ponto de vista da ecologia da paisagem representa matriz da paisagem, mas possui pequenos fragmentos altamente expostos as pressões do meio, bem como o uso conflitante de áreas destinadas à preservação.
A chuva é um fator ativo na erosão hídrica, sendo esta a mais danosa erosão para solos e água. Diversos métodos foram desenvolvidos para estimar o potencial da precipitação em desagregar partículas dos solos. Neste sentido, objetivo deste trabalho é estimar e mapear o potencial erosivo das chuvas, bem como o período de retorno e probabilidade de ocorrência na bacia hidrográfica dos Rios Galheirão e Roda Velha, situada no oeste da Bahia. Foram utilizados dados fornecidos de 14 estações convencionais da Agencia Nacional de águas e 20 pontos estimados por sensores orbitais (TRMM) disponibilizados pela Empresa Brasileira de Agropecuária. Os dados foram inseridos em fórmulas e posteriormente distribuídos espacialmente em ambiente SIG. Para análise comparativa dos resultados encontrados com o cenário de uso e ocupação do solo, foi utilizado o mapa disponibilizado pelo Mapbiomas. Os resultados indicam a estimativa de erosividade anual com valores de até 13,536.28 MJ.mm.ha-1.h-1 por ano. A região oeste da bacia possui os maiores índices erosivos nas áreas de intensa atividade agrícola, sendo mais intensa nos meses de maior lâmina precipitada. Os índices erosivos da bacia hidrográfica são considerados de baixa e média erosividade. Estimation of rain erosion (R) in a tropical basin in western Bahia Abstract: Rain is an active factor in water erosion, which is the most damaging erosion to soil and water. Several methods have been developed to estimate the potential of precipitation to break down soil particles. In this sense, the objective of this work is to estimate and map the erosive potential of the rains as well as the period of return and probability of occurrence in the hydrographic basin of the Rivers Galheirão and Roda Velha, located in the west of Bahia. Data provided from 14 conventional stations of the National Water Agency were used, 20 points estimated by orbital sensors (TRMM) made available by the Brazilian Agricultural Company, the data were inserted in formulas and later distributed spatially in a GIS environment. For comparative analysis of the results found the map provided by Mapbiomas was used with the land use and occupation scenario. The results indicate the annual erosivity estimate with values of up to 13,536.28 MJ.mm.ha-1.h-1 per year. Since the western region of the basin has the highest erosion rates that correspond to the areas of intense agricultural activity, being more intense in the months of greater precipitated depth. The erosive indices of the hydrographic basin are considered of low and medium erosivity.
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