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.