This study has demonstrated that for tea canopies, thematic mapper data (Landsat 5 short wave and thermal infrared bands) can be used to produce regional estimates of important surface parameters like albedo, surface temperature, net radiation and instantaneous evapotranspiration. The study has also shown that the TERGRA model can be successfully used to convert instantaneous evapotranspiration to daily evapotranspiration for tea canopies. At Kericho, the combination of remotely sensed data and TERGRA model produced point daily evapotranspiration estimates that differed from ground-based estimates (Penman and Bowen ratio energy balance methods) by up to 7%. For field #12, the range of evapotranspiration estimates (0.3 mm/day, by use of the Bowen ratio, Penman and remote sensing methods) was much smaller than the spatial variability of evapotranspiration throughout the study area (2-5 mm/day) as estimated by the remote sensing technique. When a large number of pixel values is used to estimate regional evapotranspiration, the standard error of the estimate approaches zero. Consequently, mean aerial evapotranspiration can be estimated to a better accuracy than would be possible with point based models. The study also showed that regression analysis (whereby evapotranspiration was predicted by use of remotely sensed canopy temperature) could be used to estimate regional evapotranspiration. Finally, for the specific situation at Kericho, advection was found to be virtually non-existent over mature tea canopies.

Thesis (M.S. - Watershed Management)--University of Arizona. / Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvi, 304 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 129-132).

Thesis--University of Wisconsin. / Supported in part by Environmental Science Services Administration, grant E-287-68(G).

Techn. Universiẗat, Diss., 2000-- Berlin.

Orientador: Dalva Martinelli Cury Lunardi / Banca: Denise Laschi / Banca: Raimundo Leite Cruz / Banca: Hildeu Ferreira da Assunção / Banca: Emerson Galvani / Abstract: The objective of this work was to apply the energy balance method partition of the available solar energy, in the processes of evaporation (latent heat), heating of air and the plants (sensible heat) and in the heating of the ground (flux of heat in the ground), in the Tagetes patula crop, inside and outside a greenhouse; and to compare the values of crop evapotranspiration (ETc) measured in water table lysimeters, with that estimated by the energy balance method, in two environments. The experiment was carried on the experimental area of the Department of Natural Resources - Section Environmental Sciences of the College of Agricultural Sciences, UNESP, Botucatu-SP, in the period from 21/05 to 09/08/02. The experimental area was constituted of two areas of 280m2, being one at field conditions and the other in greenhouse arch type, with covering of polyethylene of low density (HDPE), light spreading, with 150ìm of thickness, and polypropylene screen with 50% reduction of the solar radiation in the laterals. The results showed that the net radiation was distributed in 102% for LE, 2% for H and 9% for G inside a greenhouse. In the field condition, the distribution was of 95%, 14% and 13% for LE, H and G, respectively. The values of LE/Rn above of 100% must it the advection effect, having lateral transport of energy of the neighboring area for the culture, representing additional source of energy (lateral profit) for the evapotranspiration. Although the constructive characteristics of the water table lysimeters sheet allow that the superficial irrigations can be excused, in these conditions not the evaporation of the ground or the slowness in the hair ascension for interruption of the capillarity in the first centimeters of ground, more transpiration occurs. The evapotranspiration for the Bowen ratio method, presented average values of 50 and 55% greaters to the measured ones for the lysimeters... (Complete abstract click electronic access below) / Doutor

O arroz irrigado está entre os principais cereais produzidos no mundo. Determinar a evapotranspiração (ET) para as grandes áreas de arroz irrigado é um desafio devido a pouca disponibilidade de dados. Diversos Modelos de ET vêm sendo desenvolvidos com a intenção de monitorar áreas agrícolas, porém poucos estudos experimentais são realizados sobre áreas de arroz irrigado. Este trabalho tem como objetivo geral estimar a ET sobre cultivos de arroz irrigado através de um modelo que utiliza informações meteorológicas in situ (Priestley-Taylor) e outro remoto (MOD16). O Priestley-Taylor (PT) é um modelo de ET que utiliza informações de temperatura do ar e componentes relacionadas ao balanço de energia, juntamente com um parâmetro adimensional α. O modelo MOD16 foi criado para monitorar a ET em grandes áreas, utilizando informações meteorológicas de um banco de dados de reanálise juntamente com dados remotos. Ambos os métodos não apresentam calibração e validação sobre áreas de arroz irrigado no Sul do Brasil. Neste trabalho validamos estes dois modelos a partir de dois sítios experimentais com medidas de ET através da técnica de Eddy Covariance. Os resultados encontrados nesta pesquisa mostraram-se satisfatórios quando comparado o método PT com dados experimentais, recomendando-se a utilização de 1,22 do parâmetro α. A simplificação no método PT realizada a partir das componentes do balanço de energia, com substituição pela variável de radiação global através de uma regressão linear, mostrou-se válida apresentando erros poucos expressivos, e com valor de 1,18 para parâmetro α. Já o modelo de ET MOD16 mostrou-se pouco preciso sobre as áreas de arroz irrigado. A validação de ET MOD16 foi realizada sobre uma área de 3 x 3 km e pixel central, resultando em menor subestimativa do modelo para o pixel central em relação aos dados de Eddy Covariance. Além disso, a correlação foi realizada em função das variáveis ambientais, encontrando maior correlação do dado experimental com as componentes do balando de energia, enquanto o MOD16 apresentou maior correlação com a temperatura do ar. Por fim, sugerem-se melhorias na parametrização da energia disponível no modelo de ET MOD16. Além disso, a aplicação do método simplificado de PT é indicada sobre áreas de arroz irrigado. / Irrigated rice is among principal produced cereals in the world. Determining the evapotranspiration (ET) for large areas of irrigated rice is a challenge task, due to poor data availability. Several ET models have been developed with the intention of monitoring agricultural areas, however few experimental studies are accomplished on areas of irrigated rice. This study aims to estimate ET on irrigated rice crops using a model which employs meteorological information in situ (Priestley-Taylor) and one remote (MOD16). Priestley-Taylor (PT) is a model of ET that uses air temperature and related components to the energy balance as information and a dimensionless parameter α. The MOD16 model was designed to monitor ET in large areas using meteorological information obtained from the reanalysis database together with remote data. Both methods do not present calibration and validation on areas of irrigated rice in Southern Brazil. In this work we validate these two models from two experimental sites with ET measurements employing the Eddy Covariance technique. The results found in this research was satisfactory when compared to the PT method with experimental data. It was suggested 1.22 for the α parameter. The simplification in the PT method performed from the components of the energy balance, with substitution for the global radiation variable using a linear regression. It was validated with few expressive errors, with a value of 1.18 for α parameter. On the other hand, the MOD16 model did not showed good accuracy on the areas of irrigated rice. The validation of ET MOD16 was performed over an area of 3 x 3 km and central pixel, resulting in a small underestimation of the model for the central pixel in relation to Eddy Covariance data. In addition, was performed the correlation in function of the environmental variables, finding a higher correlation of the experimental data with the components of the energy balance, while the MOD16 showed a high correlation with the air temperature. Finally, it was suggested improvements in the parameterization of the available energy in the model of ET MOD16, and to indicate the application of the simplified method of PT on the areas with irrigated rice.

Doctor of Philosophy / Department of Civil Engineering / David Steward / Western Kansas has a semi-arid climate where the demand for water resources is greater than the natural supply. To meet the demand for irrigated agriculture, the groundwater has been extracted at a rate greater than the natural recharge rate, resulting in declining water table in the aquifer and reduced streamflow in the rivers and streams in the region. An assessment of the rivers in western Kansas was conducted to determine the fluxes between the river, groundwater, and the atmosphere. Riverbeds were instrumented to determine the conductivity of the riverbed sediments, the transmission losses of the Arkansas River were modeled to determine the interactions between the surface water and groundwater, and the evapotranspiration of the Arkansas River corridor was estimated using satellite remote sensing to quantify of water lost to the atmosphere. The Arkansas River and Cimarron River are shown to have a high hydraulic conductivity and a large infiltration capacity at the surface of the riverbed. However, the large surface infiltration capacity does not translate into large transmission losses, which are a fraction of the rate of the surface infiltration capacity of the riverbed. Thus, surface infiltration is only one factor of what controls the transmission losses. It is shown that transmission losses for a connected river-aquifer system are driven by induced infiltration by riparian vegetation. The interactions between the surface, groundwater and atmosphere were assessed over time, revealing that the flux to the atmosphere can be decoupled from the Arkansas River discharge and the groundwater recharge. While the declining discharge in the Arkansas River can be attributed to the extraction of groundwater resources and the management of surface water resource, the atmospheric fluxes are independent of the surface water and groundwater at an annual scale. When the river ecosystem is water stressed, the trees continue to draw water. This points to both the reliable store of water from the alluvial aquifer and the ability of the tree community to respond to water stress. While the water in the alluvial deposits are currently being lost from the system through evapotranspiration, this provides a potential store for consideration in future water management decisions.

Made available in DSpace on 2014-06-11T19:23:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-10Bitstream added on 2014-06-13T19:28:59Z : No. of bitstreams: 1 balotta_gap_me_jabo.pdf: 233319 bytes, checksum: 23b0129b8a38f43d1dd6a512cb94ef29 (MD5) / O objetivo desse trabalho foi avaliar três métodos de estimativa da evapotranspiração de referência (Hargreaves, Radiação Solar e Makkink), comparando-os com o método de Penman-Monteith, recomendado pela Organização das Nações Unidas para a Alimentação e Agricultura (FAO) como método padrão para estimativa da ETo, para o município de Pradópolis - SP. Para esse fim foi instalada no posto agrometeorológico da cidade de Pradópolis - SP uma estação meteorológica automatizada. Por intermédio desta estação foram obtidas medidas da radiação solar global, temperatura do ar, umidade relativa do ar e velocidade do vento. A análise dos resultados foi feita por uma técnica que considera os erros da ET0. O resultado da avaliação dos métodos indica um melhor ajuste para estimativa da ETo para o método de Hargreaves. Os métodos de Makkink e Radiação Solar não obtiveram um ajuste satisfatório com o do Penman-Monteith. Para avaliar métodos de estimativa da evapotranspiração deve-se considerar os erros da estimativa da ETo, evitando possíveis erros de avaliação / The aim of this investigation was to evaluate two reference methods to Monteith method, recommended by the Food and Agricultural Organization of the United Nations (FAO) as the standard method for estimating ETo in Pradópolis - SP. To this data collection, an automated weather station was installed in the meteorological station at Pradópolis - SP. Through estimate evapotranspiration (Hargreaves, Radiation and Makkink), compared to Penman-this station, we obtained measures of global solar radiation, air temperature, relative humidity and wind speed. The analysis was done by a technique that considers the mistakes of ETo, which depends on the combination of the errors of the variables that make up the estimating equations, derived from the measurement instruments used to obtain these variables. The aftermath showed a better adjustment to Hargreaves. Makkink, and Radiation methods are different from Penman-Monteith, therefore, they cannot be compared. To evaluate methods to estimate evapotranspiration and avoid possible evaluation errors, ETo estimate errors must be considered

O arroz irrigado está entre os principais cereais produzidos no mundo. Determinar a evapotranspiração (ET) para as grandes áreas de arroz irrigado é um desafio devido a pouca disponibilidade de dados. Diversos Modelos de ET vêm sendo desenvolvidos com a intenção de monitorar áreas agrícolas, porém poucos estudos experimentais são realizados sobre áreas de arroz irrigado. Este trabalho tem como objetivo geral estimar a ET sobre cultivos de arroz irrigado através de um modelo que utiliza informações meteorológicas in situ (Priestley-Taylor) e outro remoto (MOD16). O Priestley-Taylor (PT) é um modelo de ET que utiliza informações de temperatura do ar e componentes relacionadas ao balanço de energia, juntamente com um parâmetro adimensional α. O modelo MOD16 foi criado para monitorar a ET em grandes áreas, utilizando informações meteorológicas de um banco de dados de reanálise juntamente com dados remotos. Ambos os métodos não apresentam calibração e validação sobre áreas de arroz irrigado no Sul do Brasil. Neste trabalho validamos estes dois modelos a partir de dois sítios experimentais com medidas de ET através da técnica de Eddy Covariance. Os resultados encontrados nesta pesquisa mostraram-se satisfatórios quando comparado o método PT com dados experimentais, recomendando-se a utilização de 1,22 do parâmetro α. A simplificação no método PT realizada a partir das componentes do balanço de energia, com substituição pela variável de radiação global através de uma regressão linear, mostrou-se válida apresentando erros poucos expressivos, e com valor de 1,18 para parâmetro α. Já o modelo de ET MOD16 mostrou-se pouco preciso sobre as áreas de arroz irrigado. A validação de ET MOD16 foi realizada sobre uma área de 3 x 3 km e pixel central, resultando em menor subestimativa do modelo para o pixel central em relação aos dados de Eddy Covariance. Além disso, a correlação foi realizada em função das variáveis ambientais, encontrando maior correlação do dado experimental com as componentes do balando de energia, enquanto o MOD16 apresentou maior correlação com a temperatura do ar. Por fim, sugerem-se melhorias na parametrização da energia disponível no modelo de ET MOD16. Além disso, a aplicação do método simplificado de PT é indicada sobre áreas de arroz irrigado. / Irrigated rice is among principal produced cereals in the world. Determining the evapotranspiration (ET) for large areas of irrigated rice is a challenge task, due to poor data availability. Several ET models have been developed with the intention of monitoring agricultural areas, however few experimental studies are accomplished on areas of irrigated rice. This study aims to estimate ET on irrigated rice crops using a model which employs meteorological information in situ (Priestley-Taylor) and one remote (MOD16). Priestley-Taylor (PT) is a model of ET that uses air temperature and related components to the energy balance as information and a dimensionless parameter α. The MOD16 model was designed to monitor ET in large areas using meteorological information obtained from the reanalysis database together with remote data. Both methods do not present calibration and validation on areas of irrigated rice in Southern Brazil. In this work we validate these two models from two experimental sites with ET measurements employing the Eddy Covariance technique. The results found in this research was satisfactory when compared to the PT method with experimental data. It was suggested 1.22 for the α parameter. The simplification in the PT method performed from the components of the energy balance, with substitution for the global radiation variable using a linear regression. It was validated with few expressive errors, with a value of 1.18 for α parameter. On the other hand, the MOD16 model did not showed good accuracy on the areas of irrigated rice. The validation of ET MOD16 was performed over an area of 3 x 3 km and central pixel, resulting in a small underestimation of the model for the central pixel in relation to Eddy Covariance data. In addition, was performed the correlation in function of the environmental variables, finding a higher correlation of the experimental data with the components of the energy balance, while the MOD16 showed a high correlation with the air temperature. Finally, it was suggested improvements in the parameterization of the available energy in the model of ET MOD16, and to indicate the application of the simplified method of PT on the areas with irrigated rice.