O Sertão Pernambucano é caracterizado por longos períodos de secas, com um regime pluviométrico inconstante e irregular, dificultando o desenvolvimento socioeconômico da região. Neste contexto a aplicação de técnica de Sensoriamento Remoto utilizando de imagens georreferenciadas destaca-se pela relevância no monitoramento e análise da variação da cobertura vegetal e do suprimento hídrico nos reservatórios da região. Este estudo objetivou-se em avaliar as variações temporais geoespacializadas do uso e ocupação do solo, vegetação e área superficial do espelho d’água do reservatório de Poço da Cruz - PE, em uma perspectiva espectro temporal utilizando imagens datadas de 2000, 2013 e 2020, aplicando os índices espectrais MNDWI, NDWI, SAVI, IAF, dos sistemas sensores TM Landsat 5 e OLI Landsat 8, e ferramentas do projeto MAPBIOMAS da coleção 5.0. A análise do MNDWI identificou o aumento na área superficial do reservatório ao longo dos anos, ressaltando que os anos de 2000 e 2013 apresentaram um maior estresse hídrico com redução dos valores do índice. Os índices NDWI, SAVI e IAF, apontaram uma cobertura vegetal escassa e seca com baixa umidade para os anos de 2000 e 2013, entretanto, observou-se o aumento do vigor vegetativo e presença de maior umidade para o ano de 2020. Condizente com os dados obtidos para o uso e ocupação do solo pelo projeto MAPBIOMAS, indicando que houve um aumento das áreas destinadas a agricultura e pastagem no entorno do reservatório entre os anos de 2000 e 2013, bem como o incremento do seu espelho d´água.   Analysis of the Temporal Variability of Water Body in the Backwoods of the Pernambuco A B S T R A C TThe Sertão Pernambucano is characterized by long periods of drought, with an unstable and irregular rainfall regime, which hinders the socioeconomic development of the region. In this context, the application of the Remote Sensing technique using georeferenced images stands out for its relevance in monitoring and analyzing the variation in vegetation cover and water supply in the region's reservoirs. This study aimed to evaluate the geospatial temporal variations of the use and occupation of the soil, vegetation and surface area of the water mirror of the Poço da Cruz reservoir - PE, in a temporal spectrum perspective using images dated from 2000, 2013 and 2020, applying the spectral indices MNDWI, NDWI, SAVI, IAF, from the TM Landsat 5 and OLI Landsat 8 sensor systems, and tools from the MapBiomas project from the 5.0 collection. The MNDWI analysis identified the increase in the surface area of the reservoir over the years, noting that the years 2000 and 2013 showed greater water stress with a reduction in the index values. The NDWI, SAVI and IAF indexes indicated a sparse and dry vegetation cover with low humidity for the years 2000 and 2013, however, there was an increase in vegetative vigor and the presence of higher humidity for the year 2020. data obtained for land use and occupation by the MapBiomas project, indicating that there was an increase in areas for agriculture and pasture around the reservoir between 2000 and 2013, as well as an increase in its water surface.Keywords: biophysical indices; water resource; remote sensing.

Spectral indices processed from satellite data have been widely used to assess changes in land use and land cover, mainly focusing on the detection of water bodies in large areas. This article analyzed the spatial distribution of the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) using data from the MSI -Sentinel 2 sensor, in the semiarid region that comprises part of the territory of the Moxotó river basin in Pernambuco. When analyzing the dates of the images that covered periods considered rainy and dry in 2019, the dynamics of the spatial behavior of the study area was evidenced. The NDVI presented mean values equal to 0.404; 0.343; 0.179; 0.162;0.158 and 0.273, referring to June, July, September, October, November and December 2019, respectively. In the visualization of the NDVI through the georeferenced charts, a decrease was evidenced over the months and an increase in the last month studied. A similar behavior was detected in the NDWI, with a decrease over the months, except in December, which reached an average value of -0.260. In addition, from the NDWI it was possible to calculate the surface area of the Poço da Cruz reservoir, which had a slight decrease during the surveyed months. The MSI -Sentinel-2 sensor processed in the open-access software QGIS allowed the delineation of targets due to its greater spatial resolution, mainly in the Poço da Cruz reservoir in the municipality of Ibimirim and the stretch of the São Francisco River integration channel.

Remote sensing techniques are of fundamental importance to investigate the changes occurred in the terrestrial mosaic over the years and contribute to the decision-making by increasing efficient environmental and water management. This article aimed to detect, demarcate and quantify the hydric area of Poço da Cruz reservoir, located in Ibimirim, Pernambuco, semiarid region of Brazil, with modeling based on Landsat 8/OLI satellite multispectral images from 2015 to 2020, and to relate it with data from the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) satellites average rainfall. For this purpose, the Modified Normalized Difference Water Index (MNDWI) was modeled, being produced georeferenced theme maps and extracted only the pixels represented by positive spectral values, which represent water targets. The open-access software Quantum Geographic Information System (QGIS, version 2.18.16) was used for all stages of digital image processing and connection with complementary databases on the theme maps elaboration. In the results, changes in the spatial distribution of Poço da Cruz were evidenced and analyzed using precipitation data from the CHIRPS product, allowing a better understanding of the rainfall behavior in the region and its influence. The MNDWI was lined with the CHIRPS product, in which the spatial correlation between the rainy event and the water area’s delimitation is documented, especially in October 2017 (minimum values) and October 2020 (maximum values).

The study of soil cover in the wilderness of the Pernambuco State, through georeferenced images obtained by remote sensing, is of great relevance in the observation of the region as the spectral variability of the vegetation and the use and occupation of the soil. This study aimed to evaluate the NDVI (Normalized Difference Vegetation Index) and NDWI (Normalized Difference Water Index) index in the municipalities of Mirandiba, Carnaubeira da Penha and Bélem do São Francisco. Were acquired the TM Landsat 5 images from the study region referring to date of November 9, 2005 and for OLI Landsat 8 sensor the date corresponding to November 13, 2018. With the processing of these images using the free software QGIS, we found values of NDVI in the interval referring to values smaller than 0.10, at 0.60, NDWI between negative values at 0.20, being thus characterized the situation of exposed soil and sparse vegetation. The mapping of the surface area of the Pajeú river was carried out in the region of the Serrinha dam, obtaining the visualization of the water body variation during the 13 years, and the classification of the areas around this region using the project of Brazil's Annual Mapping of Soil Coverage and Land Use (MAPBIOMAS).

The semi-arid region of Northeastern part of Brazil is under changes pressures driven by human activities or climate changes. This study aims to assess the vegetation coverage in two periods, before the transposition of the São Francisco River-East axis, and after your implementation, in the Moxotó River basin using remote sensing techniques to determine vegetation indices, and investigate the behavior of vegetation in the catchment area. The Normalized Difference Vegetation Index (NDVI) and the Soil Adjusted Vegetation Index (SAVI). TM-Landsat5 image of 13/01/2009, and OLI-Landsat8 image of 04/02/2017 are used here. Radiometric calibration steps, reflectance are developed to generate thematic maps of NDVI and SAVI. The NDVI showed average values for 2009 and 2017 like 0,256 and 0,264, respectively, setting a growth of vegetation cover and photosynthetic activity. The SAVI had an average of 0,147 and 0,155 to years of 2009 and 2017, respectively. Differences were found between vegetable toppings determined by NDVI and by SAVI. The exposed soil class had greater expression when observed in the thematic maps of NDVI, once the SAVI, has the precept to reduce the brightness of the ground, and this index had a higher representation in the sparse vegetation.