As secas são fenómenos de ocorrência aleatória, de severidade incerta, encarados simultaneamente como um risco e um desastre. A sua duração, severidade e extensão espacial e a vulnerabilidade do meio onde ocorrem, determinam a sua importância a nível da região. Este trabalho tem por objectivo o desenvolvimento de metodologias e a aplicação de metodologias existentes na caracterização e predição de secas à região do Alentejo, A aplicação do SPI (Standardized Precipitation Index) e da teoria dos chorrilhos permite caracterizar quer as secas locais, em termos de duração e severidade, quer as secas regionais, em que também é avaliada a extensão espacial da seca. Nalguns locais, calculou-se o índice de Palmer, cujos resultados foram comparados ao SPI, em várias escalas temporais. A análise clássica de séries hidrológicas baseia-se em modelos de distribuição de frequências e pressupõe que a variável de interesse é aleatória, independente e identicamente distribuída. Os modelos de Markov e os modelos log-lineares baseiam-se na estrutura de dependência temporal da série. Estes modelos foram aplicados neste trabalho, com o objectivo de modelar as transições entre diferentes categorias de severidade de seca e avaliar o tempo de recorrência e o tempo de permanência em determinadas categorias.

A caracterização agroclimática de uma região tem particular importância pois permite avaliar a viabilidade da instalação de novas culturas ou variedades, em termos de disponibilidades térmicas ou hídricas, estimar datas de sementeira, de colheita e de outras operações culturais. Pretendeu-se efetuar a caracterização agroclimática da região do Ribatejo através do estudo dos padrões mensais de comportamento dos valores da temperatura do ar, precipitação e evapotranspiração potencial nas localidades de Ferreira do Zêzere, Santarém e Almeirim, no período de tempo compreendido entre 2006 e 2014. Pretendeu-se igualmente determinar o balanço hídrico de Thornthwaite & Mather (1955) e analisar os valores de armazenamento, deficiência e excesso de água no solo nas localidades consideradas. Os dados utilizados foram fornecidos pela Direção Regional de Agricultura e Pescas da Região de Lisboa e Vale do Tejo e organizados num formato padrão e o preenchimento das falhas foi efetuado através de análise de regressão linear simples (temperatura), do método MOVE2 (precipitação) e através do boletim meteorológico para a agricultura do IPMA. Nas três localidades em estudo, a temperatura máxima absoluta é atingida no mês de agosto e a temperatura mínima absoluta no mês de fevereiro. Ferreira do Zêzere é a localidade que apresenta maior precipitação anual e o oposto ocorre em Santarém. A evapotranspiração apresenta um comportamento muito similar à temperatura em todas as localidades. O balanço hídrico revelou que Almeirim e Santarém apresentam um défice de água no solo mais prolongado que Ferreira do Zêzere. Não foi possível obter uma fiável caracterização agroclimática devido à série de anos estudada ser reduzida e ao facto do estudo se ter focado em apenas dois elementos climáticos (temperatura e precipitação) e três localidades.

O desempenho dos métodos para estimar a evapotranspiração de referência (ETP) varia em função das condições climáticas locais, sendo este um fator de extrema importância quando se trata do manejo de irrigação de uma determinada cultura. Portanto, este trabalho tem como objetivo avaliar o desempenho dos métodos de evapotranspiração de referência, tomando como base o método padrão de Penman-Montheith-FAO, visando eleger os métodos mais apropriados para Alegrete/RS comparando com os métodos empíricos Jansen-Heise, Tanner e Pelton, Turc e o método do Tanque “Classe A”, além disso determinar e comparar a eficiência dos métodos empíricos com o método padrão de Penman-Montheith-FAO para a região de Alegrete. Foram utilizados dados meteorológicos dos anos de 2015 e 2016 de temperatura média do ar (tmed), temperatura máxima do ar (tmáx), temperatura mínima do ar (tmín), velocidade do vento medido a 2 metros de altura (U2), umidade relativa do ar (UR), precipitação (mm) e evaporação do Tanque “Classe A” (ECA). O saldo de radiação (Rn) foi estimado. Através dos resultados observa-se que os métodos de Jansen-Heise, Tanner e Pelton, Turc apresentaram um desempenho “sofrível” para a região, enquanto o método do Tanque “Classe A” apresentou um desempenho “ótimo”. Para a região em estudo, conclui-se que o método do Tanque “Classe A” pode ser recomendado para o cálculo da evapotranspiração de referência. A determinação da evapotranspiração de referência é considerada um procedimento de extrema importância ao setor agrícola, pois dimensiona o manejo e o sistema de irrigação, podendo ser obtida facilmente em função de ser afetada apenas por fatores climáticos. Desta forma, a escolha do método adequado para a determinação da evapotranspiração é de fundamental importância, sendo necessária a validação dos modelos, caso sejam modelos empíricos.

This study aimed to evaluate the efficiency of three species of bamboo (Guadua angustifolia, Phyllostachys aurea and Phyllostachys bambusoides) in the sanitary sewage treatment, with a vertically downward sub-surface flow root zone system, in Goiânia, GO, Brazil. Sewage from a university was applied to asbestos cement water tanks with 1,000 liters volume capacity, filled with oxisol above a 0,26 m drainage layer of gravel # 3. Bamboo seedlings were planted in nine beds and three beds remained without plants (controls). The wastewater was captured at the initial part of a facultative pond and applied to the surface of the treatment beds, three times a day, using a timer controlled pump. It was used a hydraulic retention time (HRT) of 2.3 days for 150 days and a HRT of 5.2 days for 360 days. Within the treatment beds, the wastewater was maintained two inches below the substrate surface. For a period of twelve months sewage samples were collected before and after passing through each treatment bed. The samples were submitted to laboratory testing for determination of chemical oxygen demand, biochemical oxygen demand, turbidity, ammonia nitrogen, phosphates, fecal coliforms and hydrogenic potential. The evapotranspiration rate of each treatment was measured, their efficiencies in removing the sewage pollutant load were calculated and the behavior of plants in treatment beds were observed. The results were submitted to F and Tukey (5% of probability) tests. Bamboo plants of G. angustifolia and P. bambusoides species developed normally, while the plants of the specie P. aurea had developmental delay because of the sewage application. In general, the specie G. angustifolia showed greater efficiency in removing the pollution load of all attributes. Effluent attended the Brazilian legislate for disposal in to receiving bodies. There was a higher removal of BOD and phosphate to the HRT of 5.2 days. The HRT of 2.3 days was better on removing ammonia nitrogen, while the removal of COD and fecal coliforms were not affected by different HRTs.

The determination of the correct irrigation depth for the production of tomato fruits is crucial for obtaining higher yields and higher quality fruit. The aim of this work was to evaluate the productivity and development of the hybrid fresh tomato Natália under different drip depth irrigation and two forms of manuring. The experiment was conducted in the experimental area of the Federal University of Goiás - Campus Jataí, during the months from April to September. The experimental design was randomized blocks with 4x2 factorial arrangement and four replications. Were used 4 different irrigation depth (66%, 100%, 133%, 166% of reference evapotranspiration ETo) daily of local, calculated daily by the Penman - Monteith method through the program SMAI, with data obtained from automatic weather station Jataí –GO by INMET site. The other factor studied was the manuring that was held by fertigation and conventional manuring. The fertilization was calculated according to the chemical analysis of the soil. Fertilizer application and the subdivision of the remaining fertilizer were taken in six times, with the same dosage in all treatments. Each experimental unit consisted of 3 rows with 12 plants each, being assessed only 8 plants centerline, excluding borders. The results showed that plant height and commercial productivity of irrigation depth 2 (100%) showed better performance. For the Brix value, it was found that the lower irrigation depths have favored increasing the Brix. Regarding the type of fertilizer, it was observed that fertigation requires an optimal amount of water for their efficiency. In this work the fertigation showed superior advantage than conventional manuring when combined with irrigation depth 2 (100%).

The Brazilian savanna (known as Cerrado) is an upland biome made up of various physiognomies, from herbaceous to arboreal. In this work, vegetation greenness (EVI), precipitation (PPT), and evapotranspiration (ET) data for the 2000 to 2012 period were analyzed in order to understand the phenology of the major Cerrado natural and anthropic landscapes, as well as its relation to precipitation, net primary productivity (NPP), biomass, and evapotranspiration fluxes, according to different land use scenarios. Along the 13 years under analysis, for all vegetation types the mean wet season duration varied from eight to nine months, while the growing season lasted seven to eight months. The mean start of the wet and growing seasons were very close for all land cover types during these 13 years, with the start of the wet season in August or September (with the exception of 2002 and 2007), and the start of the growing season in September or October. The mean end of the wet and growing seasons occurred in April or May and in May or June, respectively. The start, the end, and the duration of the wet and the growing seasons varied according to rainfall volume and distribution, which are affected by the El Niño and La Niña phenomena. For example, during El Niño years, the start of the wet season occurred earlier in August, and the duration of the wet season was longer than eight months. If followed by a La Niña, the start of the growing season of the vegetation occurred later in October and the duration of the season was shorter than eight months. In addition to the rainfall variability (El Niño and La Niña) and the type of vegetation (natural or anthropic grasslands), the start, the end, and the duration of the wet and growing seasons are also affected by the spatial variation (latitude and longitude). Considering the spatial variation of the start of the wet and growing seasons, the beginning was earlier in the southern portion of the Cerrado biome, in August-September and September-October, and later in the north, in November-December and October-December, respectively. The end of the season showed the same behavior, i.e. an earlier end (March-April) in the southern portion for the wet and growing seasons, while much later in the northern portion (June-July). Regarding the seasonal and phenological behavior of the different vegetation types, the green-up for all Cerrado physiognomies started in mid-September to the end of October, at the onset of the rainy season, reaching peak values from December through January, and a gradual senescence, starting as early as March or April. The total Cerrado growing season biomass for 2002 was 28 gigatons of carbon and the evapotranspiration was 1336 gigatons of water. A sample-based response associated with the area occupied by each vegetation type showed that pasture and cropland had 52% and 22% less NPP and ET than natural landscapes. The mean growing season evapotranspiration and biomass for 2002 was 576 Gt of water and 12 Gt of carbon for pasture and croplands compared to 760 Gt of water and 16 Gt of carbon for the Cerrado natural vegetation. Considering a modeled future scenario (year 2050), the ET flux from natural Cerrado vegetation was 394 Gt less than in 2002 and 991 Gt less than in a potential scenario, characterized with only natural vegetation, while the carbon was eight Gt less than in 2002 and 21 Gt less than in a pre-conversion Cerrado (potential scenario). In 2050, the sum of the pasture and cropland ET fluxes increased by 405 Gt, relative to 2002, and the carbon by 11 Gt. At last, the different land use scenarios showed that the deforestation impact until now in the fluxes of evapotranspiration and in the biomass were greater than the future scenario.

The changes in land-cover and land-use are among the main causes of a series of environmental, social, and economic impacts. In particular, the formation of artificial reservoirs, due to the construction of hydroelectric plants (HPP), has been the subject of scientific studies in the country, mainly due to the changes they cause to the environment. Specifically, the construction of the Luís Eduardo Magalhães HPP in 2001 (along the Tocantins River), in a context of large-scale constructions in the state of Tocantins, resulted in a large flooded area (~ 630 km²), significant changes in the landscape, and relocation of rural and urban populations. In this sense, this work aimed to evaluate and quantify, through various satellite datasets and land-cover and land-use mapping of the area under the influence of the reservoir of the Luís Eduardo Magalhães HPP (in the period before and after its implementation), changes in the landscape and associated biophysical parameters. At the landscape scale, the following surface parameters, derived from Terra-MODIS images, were evaluated seasonally: temperature, vegetation index, evapotranspiration, and albedo. The analysis of these data, in the spatial - temporal domains, involved three experimental models: a) considering the area of influence of the reservoir as a whole (equidistance of 30 km); b) analysis considering the equidistance or proximity to the reservoir (through buffers, latitudinal transects, and areas of interest); c) comparisons between the MODIS sensor results and the biophysical parameters obtained from Landsat images (transformed by the SEBAL algorithm). The results of our research show the potential of using remote sensing images in the study of variations of biophysical parameters. The implementation of the Luís Eduardo Magalhães HPP reservoir boosted the occupation of areas around it, especially: the São João irrigation project (irrigation from lake water), the increase in real estate speculation through the creation of new land subdivisions and closed condominiums with direct access to the lake, occupation of other areas due to the relocation of families (as in the case of the district of Luzimangues-Porto Nacional), and the creation of condominiums near the reservoir. Between 2000 and 2014, there was a 111% decrease in the Cerrado native vegetation (forest formations, grassland formations, open and dense Cerrado Strict Sensu physiognomies) and an increase of 66% in urban areas and 947% in the agricultural areas. It was also observed that almost half of the entire study area (42%) suffered some kind of alteration in the land cover. The changes observed in the local biophysical parameters were a direct result of the reservoir implantation and the State's occupation and development policies (such as soybean financing), which influenced the spatial configuration of the various land-cover classes and existing land use in the study area. As a result, a number of negative environmental / climatic impacts are already perceived in the area. Therefore, it is suggested to implement public policies regarding the systematic monitoring of biophysical parameters in the area, with a view to minimizing and mitigating more severe long-term environmental impacts.

As preocupações com o uso da terra têm permeado inúmeros estudos científicos, no âmbito nacional e internacional, voltados para a avaliação dos impactos ambientais causados pelas atividades agropecuárias. Alguns processos do ciclo hidrológico, a exemplo da evapotranspiração apresentam modificações consideráveis, devido às constantes mudanças nos usos dos solos. Desta forma, o presente trabalho busca destacar o problema das rápidas e intensas mudanças no uso do solo oriundas da expansão da atividade agropecuária e seus impactos ao meio ambiente, especialmente sobre o processo da evapotranspiração regional, na mesorregião do Sul Goiano, região típica de cerrado, localizada no centro-oeste brasileiro. A aplicação do algoritmo Surface Energy Balance Algorithm for Land - SEBAL consistiu o cerne da metodologia utilizada, com vista à estimativa dos fluxos de energia e da evapotranspiração em escala regional, obtidos com base no equacionamento do balanço de energia à superfície, complementado por dados de temperatura do ar e velocidade do vento adquiridos em estações meteorológicas (PCD s) instaladas na área de estudo. Foram utilizados dados do sensor MODIS/TERRA dos anos 2006, 2007, 2008, 2009 e 2010. O algoritmo foi testado em sua forma clássica e modificado por alterações nos critérios de seleção dos pixels âncoras, utilizados no procedimento da estimativa do fluxo de calor sensível. Pode-se concluir que a alteração dos critérios influenciou positivamente os resultados obtidos e que os valores da evapotranspiração, na região estudada, indicaram a potencialidade da metodologia empregada para o monitoramento sistemático dos componentes do balanço de energia em escala regional.

Evapotranspiration is a process of great importance in determining the water needs of a crop, noting periods of excess or scarcity of water, which is fundamental for the elaboration of the climatological water balance, an essential tool in agricultural planning. Therefore, the objective of the study was to compare the Blaney-Criddle, Camargo, Hargreaves and JensenHaise methods with the Penman-Monteith method, recommended by FAO as a standard method for estimating reference evapotranspiration and to determine the climatological water balance for the municipality of Presidente Figueiredo, AM. The meteorological data used were obtained from the Presidente Figueiredo automatic meteorological station, comprising daily data from a 10-year time series (January 2009 to December 2018). The statistical indicators used were the correlation coefficient (r), determination coefficient (r2 ), accuracy index (d) and the safety or performance coefficient (c). The classification of the Blaney-Criddle method was satisfactory, with its coefficient of performance as "great", followed by the Hargreaves and Jensen-Haise methods, "good" and "very good", respectively, and can be used by farmers in the region, while Camargo's had the worst performance, being “terrible”. There were no periods of water deficiency for the municipality of Presidente Figueiredo - AM, however from July to October were months of lower water surpluses, which may require the use of irrigation.