Abstract:In the Brazilian semi-arid region, the intensification of agriculture results in a change of natural vegetation by irrigated crops. To quantify the contrast between these two ecosystems, the large-scale values of water productivity components were modelled in Petrolina (PE) and Juazeiro (BA) municipalities. The SAFER (Simple Algorithm For Evapotranspiration Retrieving) algorithm was used to acquire evapotranspiration (ET), while the Monteith's radiation model was applied for estimating the biomass production (BIO). Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images were used together with agro-meteorological data. In Petrolina and Juazeiro, the mean monthly ET values for irrigated crops were 938 and 739 mm·month .Water productivity (WP) was analysed by the ratio of BIO to ET, defined here as the ratio of the net benefits from the mixed agricultural systems to the amount of water required for producing those benefits. The highest incremental WP values, as a result of the irrigated crops introduction, happened outside the rainy period. More spatial WP uniformity occurred in natural vegetation, when comparing with irrigated crops. The most frequent WP values in Petrolina were between 1.6 and 2.2 kg·m . The differences between the municipalities can be mainly explained by differences in precipitation and soil OPEN ACCESSRemote Sens. 2013, 5 5784 water storages conditions, promoting better rainfall use efficiency by the natural vegetation in the first one. The results of the current research are important for appraising the land use change impacts in situations of expanding irrigation areas.

The energy balance (EB) components were quantified in a commercial farm with corn crop, irrigated by central pivots, in the Northwestern side of São Paulo state, Southeast Brazil. The SAFER (Simple Algorithm For Evapotranspiration Retrieving) was applied to retrieve the latent heat flux (λE), considering six pivots, covering irrigated areas from 74 to 108 ha. With λE quantified and considering soil heat flux (G) as a fraction of net radiation (R n), the sensible heat flux (H) was acquired as a residual in the energy balance equation. Seven Landsat satellite images, covering all corn crop stages from 23 April 2010 to 29 August 2010, allowed relating the energy balance components according to the accumulated degree-days (DD ac) from the planting to harvest dates. The average R n values ranging from 5.2 to 7.2 MJ m-2 day-1 , represented 30 to 45% of global solar radiation (R G). Considering the variation of the energy balance components along the corn crop growing seasons, the average ranges for λE, H and G were respectively 0.0 to 6.4 MJ m-2 day-1 ,-1.5 to 6.7 MJ m-2 day-1 and 0.1 to 0.6 MJ m-2 day-1. The fraction of the available energy (R n-G) used as λE was from 0.0 to 1.3 indicated a good irrigation management, insuring that the water deficit could not be the reason of any yield reduction. Although R n did not reflected well the crop stages, its partition strongly depended on these stages. λE higher than R n and the negative H/R n , happened sometimes along the corn growing seasons. This occurred after the vegetative growth and before the harvest times, indicating heat advection from the surrounding areas to the irrigation pivots, which represented an additional energy source for the evaporative process. The models applied here with only the visible and infrared bands of the Landsat sensor are very useful for the energy balance analyses, considering the size of the corn crop irrigation pivots in Southeast Brazil, when subsidizing a rational irrigation water application in corn crop.

"Large-scale radiation and energy balances with Landsat 8 images and agrometeorological data in the Brazilian semiarid region,"

A B S T R A C TThe Cabeceira Comprida stream's watershed, located in Santa Fé do Sul, São Paulo state, has great environmental importance. It is essential for supplying water to the population and generating surpluses for sewage dilution. This study aimed to evaluate the annual performance of the components of water productivity from Landsat-8 images of 2015, using the Simple Algorithm for Evapotranspiration Retrieving (SAFER), calculating the actual evapotranspiration (ET a ), biomass (BIO) and water productivity (WP). The annual averages of ETa, BIO and WP were 1.03 mm day -1 , 36.04 kg ha -1 day -1 and 3.19 kg m -3 , respectively. The average annual values of ET a for land use and occupation were 1.40, 1.23, 1.05, 0.97 and 1.08 mm day -1 for the remaining forest (RF), invasive species (IS), pasture (Pa), annual crop (AC) and perennial crop (PC), respectively, with BIO of 57. 64, 46.10, 36.78, 32.69, 40.03 kg ha -1 day -1 for RF, IS, Pa, AC and PC, respectively, resulting in WP of 3.94, 3.59, 3.25, 3.09, 3.35 kg m -3 for RF, IS, Pa, AC and PC, respectively. The ETa, BIO and WP adjust to the seasonality of the region, and RF and IS stood out with the highest values.Produtividade da água estimada pelo SAFER -Simple Algorithm for Evapotranspiration Retrieving em bacia hidrográfica R E S U M OA Bacia Hidrográfica do Córrego Cabeceira Comprida localizada no município de Santa Fé do Sul-SP, tem grande importância ambiental, sendo imprescindível para o abastecimento de água à população e para gerar excedentes para a diluição do esgoto gerado. Assim, este trabalho avaliou o comportamento anual dos componentes da produtividade da água a partir de imagens do Landsat-8 do ano 2015, utilizando-se o 'Simple Algorithm for Evapotranspiration Retrieving' (SAFER), sendo calculadas a evapotranspiração atual (ET a ), a biomassa (BIO) e a produtividade da água (PA). As médias anuais da ETa, BIO e PA foram 1,03 mm dia -1 , 36,04 kg ha -1 dia -1 e 3,19 kg m -3 , respectivamente. As ETa médias anuais por uso e ocupação do solo foram 1,40, 1,23, 1,05, 0,97 e 1,08 mm dia -1 para mata remanescente (MR), espécies invasoras (EI), pastagem (Pa), cultura anual (CA) e cultura perene (CP), respectivamente, enquanto que as BIO apresentaram 57,64, 46,10, 36,78, 32,69, 40,03 kg ha -1 dia -1 para MR, EI, Pa, CA e CP, respectivamente, resultando em uma PA de 3,94, 3,59, 3,25, 3,09, 3, para MR, EI, Pa, CA e CP, respectivamente. As ET a , BIO e PA se ajustam à sazonalidade climática da região destacando-se a MR e as EI com os maiores valores.

Water productivity assessments with Landsat 8 images in the Nilo Coelho irrigation scheme  ANTÔNIO HERIBERTO DE CASTRO TEIXEIRA1; JANICE FREITAS LEIVAS1; RICARDO GUIMARÃES ANDRADE1 E FERNANDO BRAZ TANGERINO HERNANDEZ2 ¹Pesquisador doutor, grupo de Geociências, Embrapa Monitoramento por Satélite, CNPM, heriberto.teixeira@embrapa.br, janice.leivas@embrapa.br, ricardo.andrade@embrapa.br²Professor doutor, Laboratório de Hidráulica, Universidade Estadual Paulista, UNESP, fbthtang@agr.feis.unesp.br  1        Abstract The Nilo Coelho (NC) irrigation scheme, located in the Brazilian semi-arid region, is an important irrigated agricultural area. Land use change effects on actual evapotranspiration (ET), biomass production (BIO) and water productivity (WP) were quantified with Landsat 8 images and weather data in this scheme covering different thermohydrological conditions. The SAFER algorithm was used for ET acquirements while the Monteith’s radiation model was applied to retrieve BIO.  For classifying irrigated crops and natural vegetation, the SUREAL model was used with a satellite image representing the driest period of the year. The average values for ET, BIO and WP in irrigated crops, ranged, respectively, from 1.6 ± 1.9 to 4.2 ± 1.9 mm day-1; 59 ± 86 to 146 ± 91 kg ha-1 day-1;and 2.0 ± 1.5 to 3.0 ± 1.2 kg m-3. The corresponding ranges for natural vegetation (“Caatinga”) were from 1.2 ± 1.8 to 2.6 ± 1.8 mm day-1; 43 ± 78 to 76 ± 78 kg ha-1 day-1; and 1.6 ± 1.4 to 2.7 ± 1.1 kg m-3. The incremental values, which represent the effects of the replacement of natural vegetation by irrigated crops, were 40, 54 e 23%, for ET, BIO e WP, respectively. Keywords: evapotranspiration, biomass production, land use change  TEIXEIRA, A.H. de C.; LEIVAS, J.F.; ANDRADE, R.G.; HERNANDEZ, F.B.T.Análises da produtividade da água com imagens Landsat 8 no perímetro de irrigação Nilo Coelho  2        resumo O perímetro de irrigação Nilo Coelho (NC), localizado na região semiárida do Brasil, é uma importante área de agricultura irrigada. Os efeitos da mudança de uso da terra na evapotranspiração atual (ET), na produção de biomassa (BIO) e na produtividade da água (PA) foram quantificados com imagens Landsat 8 e dados climáticos neste perímetro cobrindo diferentes condições termo hidrológicas. O algoritmo SAFER foi usado para a obtenção da ET enquanto que o modelo da radiação de Monteith foi aplicado para a estnimativa da BIO. Para classificação em culturas irrigadas e vegetação natural o modelo SUREAL foi usado na imagem representativa do período mais seco do ano. Os valores médios da ET, BIO e PA nas culturas irrigadas variaram respectivamente de 1,6 ± 1,9 a 4,2 ± 1,9 mm dia-1; 59 ± 86 a 146 ± 91 kg ha-1 dia-1;e 2,0 ± 1,5 a 3,0 ± 1.2 kg m-3. Os valores correspondentes para vegetação natural (“Caatinga”) foram de 1,2 ± 1,8 a 2,6 ± 1,8 mm dia-1; 43 ± 78 a 76 ± 78 kg ha-1 dia-1; e 1,6 ± 1,4 a 2,7 ± 1,1 kg m-3. Os valores incrementais, representativos dos efeitos da substituição da vegetação natural por culturas irrigadas foram de 40, 54 e 23%, para respectivamente ET, BIO e PA. Palavras-chave: Evapotranspiração, produção de biomassa, mudança de uso da terra.

Modelling radiation and energy balances with Landsat 8 images under different thermohydrological conditions in the Brazilian semi-arid region," Proc. SPIE 9637, Remote Sensing for Agriculture, Ecosystems, and Hydrology XVII, 96370U (

RESUMOConduziu-se o presente estudo com o objetivo de se avaliar o risco de ocorrência de deficiência hídrica decendial da metade sul do estado do Rio Grande do Sul; para tanto, obtiveram-se dados diários de temperatura máxima e mínima, insolação e precipitação pluvial de nove localidades, distribuídas nas cinco regiões ecoclimáticas (Campanha, Depressão Central, Grandes Lagoas, Litoral e Serra do Sudeste) da metade sul do Estado, do período . Realizaram-se balanços hídricos decendiais seriados pelo método de Thornthwaite-Mather com capacidade de armazenamento de água no solo de 50 e 125 mm. A partir daí, obteve-se o índice hídrico decendial (IH = ETR/ETo). Para analisar o risco de ocorrência de deficiência hídrica adotou-se o limite 0,6 como valor crítico. Os resultados mostram que a região da Campanha é a de maior probabilidade de ocorrência de deficiência hídrica decendial, principalmente no período compreendido entre o 2º decêndio de dezembro e o 2º de janeiro.Palavras-chave: balanço hídrico, índice hídrico, evapotranspiração real, evapotranspiração potencial Risk of water deficit in ten days interval in the southern half of the Rio Grande do Sul State ABSTRACTThe objective of this study was to analyze the risk of occurrence of water deficit for periods of ten days in the southern half of the Rio Grande do Sul State. Daily meteorological data were obtained from nine localities, distributed over the five ecoclimatic regions (Campanha, Depressão Central, Grandes Lagoas, Litoral and Serra do Sudeste) of the southern half of the state, during the period of 1961 -1990. Ten days intervals water balances were computed, using the Thornthwaite-Mather method, with a soil water storage capacity of 50 and 125 mm. From these computations, the ten days water index (IH = ETR/ETo) was obtained. In order to verify the risk of occurring a water deficit, the value of 0.6 was adopted as critical value. Analysis of the results show that the Campanha region has the largest probability of occurrence of water deficit in a ten days period, mainly in the period between 2 nd ten days of December to 2 nd ten days of January.

MODIS images during the year 2012 were used for modelling of the radiation and energy balance components with the application of the SAFER algorithm (Simple Algorithm for Evapotranspiration Retrieving) in the Brazilian Pantanal area. Pixels from the main sub-regions of Barã o de Melgaç o (BR), Paiaguá s (PA) and Nhecolâ ndia (NH) were extracted in order to process microclimatic comparisons. In general, the net radiation (Rn) relied much more on the global solar radiation (RG) levels than on water conditions and ecosystem types, in accordance with the low Rn standard deviation values. The fraction of the available energy used as latent heat flux (λE) were, on average, 65, 50 and 49% for the BR, PA and NH sub-regions, respectively. Horizontal heat advection, identified by the negative values of sensible heat flux (H), made several pixels with λE values higher than those for Rn in the middle of the year. Taking the evaporative fraction (Ef) as a surface moisture indicator, the Tree-Lined Savanna (TLS) was considered the moister ecosystem class, with 58% of the available energy being used as λE, while the driest one was the modified ecosystem Anthropogenic Changes (AC), presenting a λE/Rn fraction of 0.46. According to the spatial and temporal consistencies, and after comparisons with other previous point and large-scale studies, the SAFER algorithm proved to have sensibility to quantify and compare the large-scale radiation and energy balance components in the different ecosystems of the OPEN ACCESS Remote Sens. 2015, 7 14598Brazilian Pantanal. The algorithm is useful for monitoring the energy exchange dynamics among the different terrestrial and aquatic ecosystem types throughout the seasons of the year.