Adunias dos Santos Teixeira

Avaliação da vulnerabilidade ambiental de reservatórios à eutrofização

This work presents a tool to analyze the vulnerability of reservoirs to eutrophication, aiming to subsidize control and remediation actions related with this process. It was analyzed the water basins of Araras, Edson Queiroz and Jaibaras reservoirs, located in the Acarau watershed, Ceara, Brazil. The multi-criteria analyses methodology used, in order to define environmental vulnerability indicators to reservoir eutrophication, considered reservoir sensibility and pressure factors in the water basin responsible for the transport of sediments and nutrients to the reservoir. A Geographic Information System (GIS) with map algebra as major tool was applied to soil use and occupation, declivity and erosion indicators. It was identified high vulnerability to eutrophication in the three mentioned reservoirs because of the waterbasins susceptibility to erosion, high phosphorous load mainly from the extensive cattle raising and low relative depth of the reservoirs.

Biophysics variables seasonality on surface in semiarid regions by using remote sensing

To investigate the rainfall regime effects over the albedo, NDVI (normalized difference vegetation index), net radiation and soil heat flux in a semiarid region (Northeast of Brazil), a study in the Trussu watershed was developed by using remote sensing. The study focuses on two images (Landsat 7 ETM+) provided by Instituto Nacional de Pesquisas Espaciais (INPE), from October 25, 2000 and July 24, 2001, each of them having a different rainfall regime (dry and wet seasons). The images were analyzed by using the SEBAL algorithm (surface energy balance algorithm for land). The results showed that the amount of rainfall affected the investigated variables, and the highest values of albedo were registered during the dry season. The NDVI presented high sensibility to rainfall regime, pointing out a high vegetation potential recover during the rainfall season. The NDVI along the Trussu River was up to 0.39, expressing the repair zone preservation. The watershed vegetation showed a high resilience power expressed by NDVI values in the year of 2001. Net radiation and soil heat flux were greater in the dry season, in this way expressing the effect of humidity on the energy balance.

Potential of multispectral and hyperspectral data to detect saline-exposed soils in Brazil

Irrigation-induced soil salinization is an important land degradation process in northeastern Brazil. We used multispectral and hyperspectral sensors to detect saline-exposed soils in an area cultivated with irrigated rice. Spectral mixture analysis (SMA) was applied to Operational Land Imager (OLI)/Landsat-8 data to identify exposed soils. By measuring the electrical conductivity (EC) of soil samples from 53 sites, we classified them into saline and non-saline. The surface reflectance Thematic Mapper /Landsat-5 product was used to inspect the normalized difference vegetation index (NDVI) variations over time (1984–2011) at the sites. Using OLI/Landsat-8 and Hyperion/Earth Observing One, we obtained five salinity indices and scores from principal component analysis applied to exposed soil pixels. These indices along with the first principal component (PC1) were regressed against EC to estimate soil salinization. Different metrics and support vector machine (SVM) were tested to discriminate saline and non-saline soils. The results showed that exposed soils detected by SMA had NDVI with a lower mean and standard deviation over time in the saline areas due to vegetation growth limitation. NaCl absorption bands were not observed in the Hyperion spectra due to atmospheric water vapor. Therefore, soil salinity detected by OLI or Hyperion was due to soil brightness rather than absorption bands. Because most salinity indices and scores expressed brightness to some extent, they were correlated with EC, especially the Salinity Index and PC1. However, compared with OLI, the narrow-band salinity indices of Hyperion produced a lower root mean square error for EC estimates, better discrimination between saline and non-saline soils using the Euclidean distance and spectral angle metrics, and higher SVM classification accuracy.

Monitoring soil coverage and yield of cowpea furrow irrigated with saline water

Feijao-de-corda e uma cultura de grande importância socioeconomica no Nordeste brasileiro. O objetivo deste trabalho foi avaliar a aplicacao de agua salina em diferentes estadios de desenvolvimento e no rendimento do feijao-de-corda (caupi) e alteracoes em caracteristicas do solo. O experimento foi conduzido no campo, durante a estacao seca em um delineamento em blocos casualizados com cinco tratamentos e cinco repeticoes. Cada unidade experimental constou de 4 linhas de plantio com 5,0 m de comprimento. Os tratamentos avaliados foram: 1. irrigacao com agua subterrânea com a condutividade eletrica (CEa) de 0,8 dS m -1 durante todo o ciclo da cultura; 2. agua salina (5,0 dS m -1 ) durante todo o ciclo; 3, 4 e 5. irrigacao com agua salina ate 22, de 23 a 42 e de 43 a 62 dias apos o plantio, respectivamente, e no resto do ciclo irrigada com agua subterrânea. A cobertura do solo foi avaliada por imagens digitais e utilizou-se o software ENVI para processamento e classificacao. Verificou-se que o uso continuo de agua salina inibiu o crescimento das plantas, enquanto a irrigacao com agua salina durante a germinacao e o crescimento inicial retardou o desenvolvimento, mas no ultimo caso, a recuperacao foi observada na parte final do periodo experimental. Para os tratamentos 2 e 3, foi verificada reducao no numero de vagens e na producao de sementes, em comparacao com outros tratamentos. A irrigacao com agua salina durante 20 a 40 e 40 a 60 dias apos a germinacao nao afetou o crescimento vegetativo e reprodutivo, sendo que a aplicacao de agua salina na pre-floracao (tratamento 4) causou antecipacao do ciclo reprodutivo.

Avaliação de sensor capacitivo para o monitoramento do teor de água do solo

This paper aims to evaluate a capacitance sensor for monitoring soil water content. Capacitance sensors were tested to evaluate the effect of temperature and response time, and to obtain the calibration equation and their sensitivity. Sensors were placed in different environments (soil, water and air) and temperatures (25 oC, 20 oC, 15 oC, 10 oC, 5 oC and 0 oC). The calibration was performed with one of the capacitance sensors installed in a PVC column containing 0.015066 m3 of undisturbed soil and hanged on one side of a scale with a load cell connected to a data acquisition board on the other side. Results showed reductions in the frequency response of the capacitance sensor with increasing temperature. The response time was low (less than one second) as it was immersed into water, as well as to an abrupt change in soil moisture in the soil column. It was verified that the sensitivity of the sensor increases as the soil moisture decreases. Therefore, the capacitance sensor can be used to determine the soil moisture.

Laboratory Salinization of Brazilian Alluvial Soils and the Spectral Effects of Gypsum

Irrigation-induced salinization is an important land degradation process that affects crop yield in the Brazilian semi-arid region, and gypsum has been used as a corrective measure for saline soils. Fluvent soil samples (180) were treated with increasing levels of salinization of NaCl, MgCl2 and CaCl2. The salinity was gauged using electrical conductivity (EC). Gypsum was added to one split of these samples before they were treated by the saline solutions. Laboratory reflectance spectra were measured at nadir under a controlled environment using a FieldSpec spectrometer, a 250-W halogen lamp and a Spectralon panel. Variations in spectral reflectance and brightness were evaluated using principal component analysis, as well as the continuum-removed absorption depths of major features at 1450, 1950, 1750 and 2200 nm for both the gypsum-treated (TG) and non-treated (NTG) air-dried soil samples as a function of EC. Pearson’s correlation coefficients of reflectance and the band depth with EC were also obtained to establish the relationships with salinity. Results showed that NTG samples presented a decrease in reflectance and brightness with increasing CaCl2 and MgCl2 salinization. The reverse was observed for NaCl. Gypsum increased the spectral reflectance of the soil. The best negative correlations between reflectance and EC were observed in the 1500–2400 nm range for CaCl2 and MgCl2, probably because these wavelengths are most affected by water absorption, as Ca and Mg are much more hygroscopic than Na. These decreased after chemical treatment with gypsum. The most prominent features were observed at 1450, 1950 and 1750 nm in salinized-soil spectra. The 2200-nm clay mineral absorption band depth was inversely correlated with salt concentration. From these features, only the 1750 and 2200 nm ones are within atmospheric absorption windows and can be more easily measured using hyperspectral sensors.

Avaliação do tensiômetro eletrônico no monitoramento do potencial matricial de água no solo

This paper presents the monitoring of the soil matrix potential using the electronic tensiometer. The trials were conducted at the Mechanics and Electronics Lab of the Department of Agricultural Engineering of the Federal University of Ceara. Nine samples of electronic tensiometers and three conventional mercury tensiometers were tested for a month period of data gathered at a 2 Hz frequency. The monitoring made it possible to produce insights on the soil drying process, on the effect of temperature fluctuation on the readings, and it was possible to evaluate the response time and sensitivity of the electronic tensiometer. It was found that the temperature effect on the readings increases as the matrix potential decreases, thus it is essential to install temperature sensors on the electronic tensiometers in order to remove the errors induced by temperature variation especially if the sensors are to be used at the peak hours. The response time increases as the matrix potential decreases and the tensiometers tested presented average sensitivity of 42.833 mV(kPa)-1, and precision of 0.02334 kPa or 0.2380 cm c H2O.

Mudanças climáticas e impactos na necessidade hídrica das culturas perenes na Bacia do Jaguaribe, no Estado do Ceará

The aim of this study was to estimate climate change impacts on irrigation water demand for permanent crops. The PRECIS (Providing Regional Climates for Impact Studies) system was applied, and downscaling techniques were used at the river basin level, with the boundary conditions of the regional climate model (HadRM3P). A climate data set was generated for 1961 to 1990 (baseline) and for future climate projections. The regional geographical coordinates were considered for interpolation in a georeferenced coordinated system. The reference evapotranspiration was estimated through data of monthly average temperature. Projected climate change increased projected irrigation water demand, because evapotranspiration was estimated to increase by 3.1 to 2.2% and rainfall was estimated to decrease by 30.9 to 37.3%. The 2040 water need was estimated to increase by 32.9% to 43.9%, according to the analyzed scenario.

Hyperspectral Remote Sensing for Detecting Soil Salinization Using ProSpecTIR-VS Aerial Imagery and Sensor Simulation

Soil salinization due to irrigation affects agricultural productivity in the semi-arid region of Brazil. In this study, the performance of four computational models to estimate electrical conductivity (EC) (soil salinization) was evaluated using laboratory reflectance spectroscopy. To investigate the influence of bandwidth and band positioning on the EC estimates, we simulated the spectral resolution of two hyperspectral sensors (airborne ProSpecTIR-VS and orbital Hyperspectral Infrared Imager (HyspIRI)) and three multispectral instruments (RapidEye/REIS, High Resolution Geometric (HRG)/SPOT-5, and Operational Land Imager (OLI)/Landsat-8)). Principal component analysis (PCA) and the first-order derivative analysis were applied to the data to generate metrics associated with soil brightness and spectral features, respectively. The three sets of data (reflectance, PCA, and derivative) were tested as input variable for Extreme Learning Machine (ELM), Ordinary Least Square regression (OLS), Partial Least Squares Regression (PLSR), and Multilayer Perceptron (MLP). Finally, the laboratory models were inverted to a ProSpecTIR-VS image (400–2500 nm) acquired with 1-m spatial resolution in the northeast of Brazil. The objective was to estimate EC over exposed soils detected using the Normalized Difference Vegetation Index (NDVI). The results showed that the predictive ability of the linear models and ELM was better than that of the MLP, as indicated by higher values of the coefficient of determination (R2) and ratio of the performance to deviation (RPD), and lower values of the root mean square error (RMSE). Metrics associated with soil brightness (reflectance and PCA scores) were more efficient in detecting changes in the EC produced by soil salinization than metrics related to spectral features (derivative). When applied to the image, the PLSR model with reflectance had an RMSE of 1.22 dS·m−1 and an RPD of 2.21, and was more suitable for detecting salinization (10–20 dS·m−1) in exposed soils (NDVI < 0.30) than the other models. For all computational models, lower values of RMSE and higher values of RPD were observed for the narrowband-simulated sensors compared to the broadband-simulated instruments. The soil EC estimates improved from the RapidEye to the HRG and OLI spectral resolutions, showing the importance of shortwave intervals (SWIR-1 and SWIR-2) in detecting soil salinization when the reflectance of selected bands is used in data modelling.

Estimativa da evaporação no açude Banabuiú, no estado do Ceará, por diferentes métodos combinados, derivados da equação de Penman

O Estado do Ceara possui 75% do territorio abrangido pelo semiarido brasileiro, com suas caracteristicas peculiares. Nesse Estado, acudes constituem-se em estrutura hidrica de importância estrategica, garantindo, no tempo e no espaco, o desenvolvimento e o abastecimento hidrico das populacoes. No entanto, a construcao de reservatorios implica varios impactos que devem ser cuidadosamente observados no momento de decidir pela sua execucao. Um dos impactos apontados como negativo e o aumento da evaporacao, que se constitui em um dos principais componentes do balanco hidrico nos reservatorios, sobretudo em regioes aridas. Varios metodos de estimativa da evaporacao foram propostos ao longo do tempo, muitos deles derivados da equacao de Penman. Neste trabalho, foram avaliados seis diferentes metodos de estimativa da evaporacao a fim de determinar qual o mais adequado para utilizacao em modelos hidrologicos para o balanco hidrico em reservatorios no Estado do Ceara. Os metodos avaliados foram os propostos por Penman, Kohler-Nordenson-Fox, Priestley-Taylor, deBruim-Keijman, Brutsaert-Stricker e deBruim, os quais apresentaram otimo desempenho quando testados para o balanco hidrico durante a estacao seca, sendo o de Priestley-Taylor o mais adequado, uma vez que os dados do balanco hidrico simulado com a componente evaporacao estimada por este metodo foram os mais proximos dos dados do balanco hidrico observado a partir das medidas de nivel do reservatorio e da curva cota-volume fornecidos pela Companhia de Gestao dos Recursos Hidricos do Estado do Ceara - COGERH.