A B S T R A C TThe surface albedo plays an important role in the exchanges of energy and mass in the planetary boundary layer. Therefore, changes in albedo affect the balance of radiation and energy at the surface, which can be detected with its monitoring. Albedo determination has been performed through various sensors, but there is not yet any publication dealing with albedo calculation procedures using OLI (Operational Land Imager) -Landsat 8 images. The objective of the study is to present the procedures for computing the albedo with OLI images and map it in irrigated areas of the São Gonçalo Irrigated District, PB, Brazil. Images of the year 2013, path 215 and row 65, were selected. The data necessary for calculating the albedo were extracted from each image metadata: additive and multiplicative terms of radiance and reflectance, and sun elevation angle. There were large differences between the albedo values of irrigated plots, water bodies and native vegetation. The albedo obtained with OLI images provides a higher degree of differentiation of the various types of land use, due to the substantial increase in the radiometric resolution of this new sensor.Procedimentos para cômputo do albedo com imagens OLI-Landsat 8: Aplicação ao semiárido brasileiro R E S U M O O albedo da superfície desempenha papel importante nas trocas de energia e massa na camada limite planetária. Neste sentido, alterações no albedo modificam os balanços de radiação e energia à superfície, que podem ser detectadas com seu monitoramento. A determinação do albedo tem sido feita através de diversos sensores mas ainda não foram publicados procedimentos de cálculo do mesmo com imagens do OLI (Operational Land Images) do Landsat 8. O objetivo do estudo é apresentar, em detalhes, procedimentos de cômputo do albedo com imagens OLI e mapear o mesmo em áreas do perímetro irrigado São Gonçalo, PB. Foram selecionadas imagens do ano 2013, órbita e ponto 215 e 65, respectivamente. Os dados necessários ao cômputo do albedo foram extraídos do meta dados de cada imagem, quais sejam: termos aditivo e multiplicativo da radiância e reflectância das bandas de 2 a 7 e ângulo de elevação do Sol. Verificaram-se grandes diferenças entre os valores do albedo das parcelas irrigadas, corpos d'água e de vegetação nativa. Concluise que o albedo obtido com as imagens OLI apresenta maior grau de diferenciação dos diversos tipos de uso da terra, resultado do aumento substancial da resolução radiométrica deste novo sensor.

Visando-se avaliar a distribuição de classes texturais e sua correlação espacial com a infiltrabilidade e salinidade de uma área aluvial, no Agreste de Pernambuco, utilizou-se a geoestatística indicadora segundo uma distribuição binária baseada na presença/ausência de solos francos. Considerando-se pontos de amostragem e de testes de infiltração dispostos ao longo do eixo principal do aluvião, e aleatoriamente distribuídos, analisou-se a variabilidade espacial das classes de solo predominantes, da velocidade de infiltração básica (condutividade hidráulica saturada) e da condutividade elétrica do extrato de saturação da camada subsuperficial, cujos alcances dos semi-variogramas ajustados foram de 333, 320 e 520 m, respectivamente. Verificou-se que a geoestatística indicadora preservou a correlação espacial entre a textura e a condutividade hidráulica, e entre a textura e a condutividade elétrica. Deste modo, as classes de solo predominantes podem ser usadas para representar distintos padrões no tocante ao potencial de lixiviação e à susceptibilidade de salinização. A metodologia indicadora mostra-se promissora para estudo da variabilidade espacial de propriedades físicas de solos aluviais onde predominam classes contrastantes.

The Ipojuca river, a river in Northeast Brazil extending from west to east, is situated in the semiarid interior and rainy coastal zone of Pernambuco state. The river basin covers an area of 3,514 km 2 , with a total river length of 215 km. The water flow regime is characterized by the annual change from dry to rainy season as well as periodically occurring dry cycles. Mean flow rates vary between 2 and 35 m 3 s −1 . The dominant impacts on water quality of the river are domestic sewage input in the upper catchment and sugar cane cultivation and processing in the lower catchment. Long-term monitoring data used to demonstrate the impact of sewage discharge on the river's self-purification capacity indicated a severe change to the worse in the lower course. One reason is the use of stillage (wastewater from cane processing) for fertilization and irrigation (fertigation). Pathways of contamination have been identified by evaluating cultivation and processing techniques of a bio-alcohol factory with annexed sugar cane cultivation. The river's main ecological problems are water heating, acidification, increased turbidity, oxygen imbalance, and increased coliform bacteria levels. Precipitation-related wash-off and wash-out causes significant contamination within one to two days after rainfall. The increase in coliform bacteria is a consequence of secondary contamination.To determine the impact of the sugar cane industry on the river, the Brazilian bio-alcohol program must be subject to a critical evaluation. Environmentally friendly sugar cane cultivation methods need to be developed, and sugar cane factories must use wastereducing technologies and water cycling processes in order to protect the region's water resources.

No abstract

Abstract. In this paper, we present and analyze a novel global database of soil infiltration measurements, the Soil Water Infiltration Global (SWIG) database. In total, 5023 infiltration curves were collected across all continents in the SWIG database. These data were either provided and quality checked by the scientists who performed the experiments or they were digitized from published articles. Data from 54 different countries were included in the database with major contributions from Iran, China, and the USA. In addition to its extensive geographical coverage, the collected infiltration curves cover research from 1976 to late 2017. Basic information on measurement location and method, soil properties, and land use was gathered along with the infiltration data, making the database valuable for the development of pedotransfer functions (PTFs) for estimating soil hydraulic properties, for the evaluation of infiltration measurement methods, and for developing and validating infiltration models. Soil textural information (clay, silt, and sand content) is available for 3842 out of 5023 infiltration measurements (∼ 76%) covering nearly all soil USDA textural classes except for the sandy clay and silt classes. Information on land use is available for 76 % of the experimental sites with agricultural land use as the dominant type (∼ 40%). We are convinced that the SWIG database will allow for a better parameterization of the infiltration process in land surface models and for testing infiltration models. All collected data and related soil characteristics are provided online in *.xlsx and *.csv formats for reference, and we add a disclaimer that the database is for public domain use only and can be copied freely by referencing it. Supplementary data are available at https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data quality assessment is strongly advised prior to any use of this database. Finally, we would like to encourage scientists to extend and update the SWIG database by uploading new data to it.

R E S U M OAs mudanças no uso e na ocupação do solo, provocadas pelas ações antrópicas, têm gerado grandes impactos nas paisagens. Esses impactos podem ser mitigados através do monitoramento do uso e da cobertura do solo utilizando-se informações espaço-temporais das modificações ocorridas na paisagem. Este trabalho apresenta uma análise espaço-temporal detalhada da dinâmica do uso e ocupação do solo da bacia hidrográfica do riacho São Paulo, localizada na região semiárida do Estado de Pernambuco, entre os anos de 1991 e 2010. Partindo da classificação de três imagens de satélite dos anos de 1991, 2000 e 2010, foram utilizadas matrizes de transição, associadas à álgebra de mapas e métricas da paisagem. Os resultados mostraram que durante o período estudado as classes de uso e ocupação do solo passaram por uma grande transição, com a substituição progressiva das áreas de vegetação de caatinga aberta por áreas com pastagem/agricultura. Junto com o rápido crescimento da classe pastagem/agricultura, a paisagem predominante de vegetação nativa foi sendo substituída por uma paisagem cada vez mais devastada, heterogênea e fragmentada, como mostraram os índices das métricas da paisagem.Dynamic of land use/cover change processes in a Brazilian semiarid watershed A B S T R A C TThe changes in the use and occupation of land, caused by human actions, have created major impacts on the landscapes. These impacts can be mitigated by monitoring the use and land cover, using spatial and temporal information of the changes occurring in the landscape. This paper presents a detailed analysis of spatial and temporal dynamics of land use and occupation of the stream São Paulo watershed, located in the semiarid region of Pernambuco State, during the period from 1991 to 2010. Based on the classification of three satellite images for the years 1991, 2000 and 2010, transition matrices were used associated with the algebra of maps, and landscape metrics. The results showed that during the studied period, the classes of land use and occupation went through a major transition, with the gradual replacement of sparse area of 'caatinga' vegetation by grazing areas/agriculture. Along with the rapid growth of the grazing areas/agriculture class, the predominant landscape of native vegetation has been replaced by a landscape increasingly devastated, fragmented and heterogeneous, as shown by the index of landscape metrics.

No abstract

Resumo -O objetivo deste trabalho foi mapear a evapotranspiração real (ETr) e determinar o volume de água utilizado no projeto de irrigação de São Gonçalo, PB, no Semiárido brasileiro, com auxílio do sensoriamento remoto. Foram adquiridas imagens TM/Landsat 5 da área em estudo, em 2008, que foram utilizadas na obtenção dos mapas temáticos da ETr diária. Selecionaram-se dois pomares de coqueiro-anão para validação dos resultados da evapotranspiração obtida com o "surface energy balance algorithm for land" (ET Sebal ) e com o método FAO-56 (ET FAO ). Para determinação da ET FAO , utilizou-se o produto entre o coeficiente de cultura, o coeficiente de ajuste e a evapotranspiração de referência. As diferenças obtidas, com uso das duas técnicas, resultaram em raiz do erro quadrado médio, erro relativo médio e erro absoluto médio iguais a 0,53 mm, 9,46% e 0,43 mm, respectivamente. Nas áreas irrigadas, a ETr representou 85% do saldo de radiação e, nas de sequeiro, apenas 12,5%. O mapeamento da ETr delimitou claramente as áreas irrigadas das de sequeiro, bem como as diferenças existentes no interior do perímetro irrigado do projeto em investigação. O volume de água empregado no projeto de irrigação representa, somente no período de julho a dezembro, mais de 60% da capacidade do açude de São Gonçalo.Termos para indexação: albedo, Landsat 5, saldo de radiação, temperatura da superfície. Evapotranspiration and assessment of water consumed in irrigated area of the Brazilian Semiarid Region by remote sensingAbstract -The objective of this work was to map the actual evapotranspiration (ETr) and to determine the volume of water used in the irrigation project of São Gonçalo, PB, in the Brazilian Semiarid Region, using remote sensing. TM/Landsat 5 images were acquired from the study area, in 2008, and were used to obtain thematic maps of daily ETr. Two dwarf coconut crops were selected for validation of the results of evapotranspiration obtained by the surface energy balance algorithm for land (ET Sebal ) and the FAO-56 method (ET FAO ). In order to determine ET FAO , the product between the culture coefficient, the adjustment coefficient, and the reference evapotranspiration was used. The differences obtained by the two techniques resulted in root mean square error, mean relative error, and mean absolute error equal to 0.53 mm, 9.46%, and 0.43 mm, respectively. In the irrigated areas, ETr represented about 85% of net radiation and, in rainfed plots, only 12.5%. The mapping of ETr clearly delimitated the irrigated and nonirrigated plots, as well as the differences within the irrigated perimeter of the project under investigation. The volume of water applied in the irrigation project, only in the period from July to December, represents more than 60% of the capacity of the São Gonçalo reservoir.