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.

The multiple use of reservoirs is widely accepted, but there are frequent conflicts between water users based on ecological, economic and sociological concerns. The promotion of aquatic ecosystem services is a successful approach to advanced reservoir management. The main aquatic ecosystem services are goods and human benefits such as clean water and hydropower. The sustainability of aquatic ecosystem services must be the aim of a reservoir management plan, and hence adequate water quality and predominantly mesotrophic conditions are necessary. However, eutrophication processes are advanced in many tropical reservoirs, and re-oligotrophication is needed, as has been successfully implemented in temperate lakes. The eutrophication processes and re-oligotrophication potential of tropical reservoirs are significantly different from temperate ecosystems. Studies to quantify the impact of ecosystem services were conducted on the Itaparica reservoir, São Francisco River, Brazil, which is located in a semi-arid area. The main disturbance to tropical reservoirs is the change in water level due to hydropower operational conditions. Desiccated areas on the lakeshore have a high potential for nutrient release by sediment mineralization. An increase in the water level promotes the growth of some pioneer plants, such as the water pest, Egeria densa. Intensive net cage aquaculture can lead to an overcharge of the reservoir, and therefore the carrying capacity should be considered. Furthermore, sediment management and the abstraction and re-use for soil amendment has to be managed. The multiple water uses and sustainability of aquatic ecosystem services must be the aim of any reservoir management plan, and the eutrophic level is a key factor due to its impact on water quality.

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Finfish aquaculture in net cages is widely used in Brazilian reservoirs, mainly for tilapia production. There is a large and increasing potential for production in the São Francisco river basin, and particularly the Itaparica reservoir. Tilapia production amounts to 24,000 t y-1 , with a licensed amount of 43,267 t y-1. This intensive fish production in net cages is responsible for a significant biological oxygen demand, and phosphorus and nitrogen load on the reservoir, which promotes eutrophication. Particulate organic matter released from the net cages accumulates beneath the net cages, and a minimum water depth beneath the net cages of 10 m is required to limit the sediment increase to a few millimetres per year. Modeling of Icó-Mandantes bay has identified a reduced water exchange within the bay. Modeling of the effect of net cage aquaculture within the Icó-Mandantes bay points out clearly the significant increase in dissolved phosphorus and the accumulation inside the bay area. The carrying capacity of the reservoir was determined using the P load model, with a critical P concentration based on the phosphorus use efficiency. The critical P concentration amounts 25 µg L-1 , and the critical P load of the reservoir amounts 2.84 g m-2 y-1 ; the actual load is already 3.30 g m-2 y-1 , such the reservoir is already overcharged by nutrients. A sustainable "blue" aquaculture must be implemented based on use of advanced systems, species selection, fish feed, and linked production systems.

In the analysis of trophic state of the water body is fundamental to know chlorophyll-a concentration. Thus, this work has as main aim to determinate and to assess the behavior of chlorophyll-a in the Itaparica reservoir, São Francisco river. This way, we used Landsat-TM imagery, in which it was used bands from 1 to 5 and 7. The algorithm used was written in LEGAL/SPRING 5.2. From the chlorophyll-a result was held slicing the water body in six concentration classes. As observed by histogram, the minimum value of Chl-a was < 1 µg/L and the highest was 249.5 µg/L. The classes that had the biggest area were Classe 01 (0-5 µg/L) with 27.4%, followed by Classe 02 (5-10 µg/L) with 24.6% of the total area of the study area. Through graphical analysis of points located along the reservoir it was possible to verify that chlorophyll concentration augmented from fluvial to lacustrine region and from the contact of streams with reservoir. In the next studies there is a need to validate the values with field data in order to verify the mapping accuracy in this reservoir, taking into account the day and also the transit time of the sensor.

R ESU M OO estudo da umidade do solo é fundamental não só para a determinação da resiliência de ecossistemas e sua recuperação, mas também na modelagem da relação água-vegetação-atmosfera. Na aquisição dessas informações o sensoriamento remoto perfaz uma ferramenta importante e de potencial adequado para monitoramento e mapeamento. Visando à espacialização de índices relacionados à umidade, vários métodos têm sido propostos, embora sua aplicação ainda seja limitada. Neste trabalho se aplicou o modelo de índice de umidade do solo (IUS) cujos objetivos foram: espacializar o IUS, estabelecer graus de desertificação, delimitar a área em processo de desertificação e verificar possíveis relações do IUS com parâmetros de água no solo. Na aplicação deste modelo se utilizaram, como dados de entrada, o NDVI (índice de vegetação da diferença normalizada) e a LST (temperatura da superfície) e se observou que o IUS representado pela média dos valores desses índices pode ser empregado na determinação do grau de degradação da superfície e para gerar classificação legendada, discriminando vários níveis de degradação ambiental. Constatou-se também que não houve relação direta do IUS com parâmetros físicos de retenção de umidade do solo. Desta forma, o sensoriamento remoto mostrou ser uma ferramenta significativa na avaliação de índices de umidade do solo em áreas degradadas tal como para delinear a dinâmica de borda em núcleo de desertificação.Palavras-chave: índice de umidade do solo, NDVI, Seridó, desertificação Spatial distribution of soil moisture using land surface temperature and vegetation indices A B ST R A C TThe study of soil moisture is important in determining the resilience of ecosystems and their recovery, as well as in the modeling of water-vegetation-atmosphere relationship. Remote sensing is an important tool for the acquisition, mapping and monitoring soil moisture through the surface temperature and vegetation indices. For the soil moisture content assessment, several methods have been proposed, however its application is still limited. In this work the soil moisture index (SMI) was applied and modeled with the objectives: to establish and delineate areas with different levels of desertification through SMI mapping and to map the dynamic of border, as well as to verify possible relationships betweem SMI and soil water parameters. In the application of this model as input data was used: NDVI (normalized difference vegetation index) and LST (land surface temperature). It was observed that SMI accessed by the average of the SMI derived by NDVI and LST can be used in the determination of soil surface degradation and in the production of maps showing different levels of this degradation. It was also verified, that there was no direct relationship between SMI and physical parameters of soil moisture content. Remote sensing showed to be an important tool in the evaluation of soil moisture indices in degraded areas and to delineate the border effect in this desertification nucleus.

RESUMOO estudo de parâmetros biofísicos como o Índice de Vegetação da Diferença Normalizada (NDVI), albedo e temperatura da superfície (LST), aplicado a ecossistemas, tem sido relevante para o entendimento de mudanças relacionadas à degradação do meio ambiente. Algumas alterações que provocam desequilíbrio de interações ecológicas em ecossistemas, como o desmatamento, a mineração, a agricultura inadequada e o superpastejo, entre outros, estão interrelacionadas. Para avaliação de mudanças temporais relacionadas à degradação do ecossistema caatinga obtiveram-se as imagens da diferença de três parâmetros: NDVI, albedo e temperatura da superfície, para os anos de 1985 e 2001 (estação seca), utilizando-se imagens TM. Este estudo foi aplicado à bacia do rio Brígida onde há uma exploração intensa dos recursos naturais, em que os resultados mostram aumento na temperatura da superfície, diminuição do NDVI e pouca variação no albedo da superfície evidenciando, assim, que entre os anos de 1985 e 2001 houve avanço na degradação dos recursos naturais, nesta bacia.Palavras-chave: temperatura da superfície, albedo, índice de vagetação, degradação da caatinga, modelagem de dados Biophysical parameters in the detection of changes in soil cover and use in watersheds ABSTRACTThe study of biophysical parameters such as NDVI, albedo and surface temperature has been reported as important for the understanding of land degradation changes of ecosystems. Degradation in ecosystems is related to the inadequate use of the environmental resources including deforestation, mining, inadequate agriculture, overgrazing, among others, that cause imbalance of ecological interactions. For multitemporal evaluation of changes related to the degradation of the 'caatinga' ecosystem three parameters were used with TM images: NDVI, albedo and surface temperature, in two different dates, 1985 and 2001 (dry season). This study was applied in the Brígida river basin where there is a great intensification in the exploration of the natural resources. The results show an increase in the surface temperature, decrease of NDVI and little variation in the surface albedo, between the two dates. These results also show an increase in the degradation of the natural resources in the basin of the Brígida river.

resumo Elaborado com base na análise de dados oficiais, documentos internacionais, textos legislativos e extensa revisão bibliográfica, este artigo apresenta algumas reflexões sobre temas relevantes à implementação, pelas cidades brasileiras, dos Objetivos do Desenvolvimento Sustentável, fixados pela Agenda 2030 para o Desenvolvimento Sustentável da Organização das Nações Unidas, apontando os instrumentos legais existentes no âmbito da Política Nacional do Meio Ambiente, Política de Gestão de Recursos Hídricos, Estatuto da Cidade e Política Nacional de Proteção e Defesa Civil, com ênfase às ações e estratégias urbanas de mitigação, adaptação e resiliência às mudanças climáticas, no intuito de contribuir, na universidade, para a orientação de pesquisas científicas inter e transdisciplinares, articuladas com a formulação, implementação e avaliação de políticas públicas e voltadas a prover soluções para o enfrentamento dos complexos desafios de gestão e planejamento enfrentados pelas cidades contemporâneas.