scholarly journals REFERENCE EVAPOTRANSPIRATION THROUGH HARGREAVES METHOD USING THE SOLAR RADIATION ESTIMATION FOR GOIÁS STATE, BRAZIL

2020 ◽  
Vol 28 ◽  
pp. 274-292
Author(s):  
Caio Vinicius Leite ◽  
Derblai Casaroli ◽  
Marcelo Rossi Vicente ◽  
Raphael Cessa Maia Aveiro ◽  
José Alves Júnior

This study evaluated the Hargreaves model (HG) with seasonal adjustments of the calibration coefficient (Krs) of the radiation equation to estimate the reference evapotranspiration (ETo) in 23 weather stations in Goiás State, Brazil, in comparison to the Penman-Monteith FAO (PM-FAO) standard method. The models were evaluated using Pearson’s correlation coefficient, Willmott’s agreement index, relative error, absolute mean error and root mean square error. The Krs values ranged from 0.146 to 0.189 ° C-0.5, while ETo PM-FAO ranged from 3.68 to 4.79 mm d-1; ETo HG from 3.99 to 5.16 mm d-1 and ETo HG-Krs from 4.15 to 5.02 mm d-1 in the annual period. Seasonal adjustments resulted in values of 0.144 to 0.205 ° C-0.5 for the dry period, from April to September, and 0.144 to 0.146 ° C-0.5 for the rainy period, from October to March. The first quarter (summer), presented Krs values from 0.150 to 0.175 ° C-0.5; the second quarter (autumn), from 0.154 to 0.218 ° C-0.5; the third quarter (winter), from 0.139 to 0.206 ° C-0.5; and, finally, the fourth quarter (spring) of 0.141 to 0.166 ° C-0.5. Thus, the use of the seasonally adjusted model proved to be viable for the estimation of ETo, in view of the simplicity and its good adherence to the standard method.

2019 ◽  
Vol 11 (18) ◽  
pp. 63
Author(s):  
P. A. L. de Castro ◽  
G. O. Santos ◽  
R. G. Diniz

The water management in irrigated agriculture begins determining the need of water for the culture. Therefore, it was intended to evaluate the performance of the models of estimation reference of evapotranspiration (ETo) with regard to the method Penman-Monteith (PM), standard method, for Brazilian Cerrado Region (tropical grassland/savannah). The climate elements were obtained from the conventional weather station of Rio Verde from January/1972 to December/2016. It was compared the performance of the daily average ETo, during the dry, rainy and annual periods, by the PM method with regard to another 26 methods. Through the coefficient of determination, it was verified the methods of Turc (T) and Radiation-Temperature (RT) approached more to the PM, at any time of the year, being able to replace the standard method. The ETo average in the annual period was 3.8 mm day-1, for the dry period due to the smallest amount of solar radiation, the period submitted lower levels of ETo. The other models in which were used fewer amounts of climate data, they overestimated or underestimated the PM model by up to 57.9% and 60.7% respectively. With the management of water in agriculture, water availability can be increased in the hydric bodies, characterizing it as a tool for water management with the rational use of water resources.


Nativa ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 106-114
Author(s):  
Ewerton Medeiros Simões ◽  
Joedla Rodrigues de Lima ◽  
Izaque Francisco Candeia de Mendonça

No semiárido brasileiro, onde se insere o bioma caatinga, a precipitaçãos é um dos fator limitante para seu desenvolvimento sócioeconômico e ambiental, este estudo avaliou a correlação existente entre o nível de cobertura vegetal e as variáveis pluviométricas locais, considerando a climatologia de 2005 e 2015, utilizando-se imagens dos sensores TM e OLI dos satélites Landsat 5 e Landsat 8, respectivamente. O ano de 2005 apresentou maiores valores de NDVI em relação a 2015, com valores máximos de 0,71 e 0,78 no período seco e úmido, respectivamente. No ano de 2015, os valores máximos são de 0,64 e 0,61, para o período seco e úmido, respectivamente. Os maiores valores foram observados no período chuvoso de 2005, nas áreas de influência das estações meteorológicas de Matureia, Salgadinho e Areia de Baraúnas. No período seco, nota-se a baixa variabilidade dos valores de NDVI, sendo as maiores leituras observadas nas estações de Matureia, Salgadinho e Teixeira. As estações que apresentaram as maiores reduções nos valores de NDVI de 2005 para 2015, no período chuvoso, foram Matureia, Santa Teresinha e Salgadinho, com reduções de 41,9%, 38,2% e 32,7%, respectivamente. As correlações mais significativas foram estabelecidas para os períodos secos. As menores correlações foram verificadas no período chuvoso. A elevação dos níveis pluviométricos na região não implicou o aumento progressivo nos valores de NDVI. Palavras-chave: semiárido; geoprocessamento; índice de vegetação normalizada.   Normalized difference vegetation index associated with pluviometric variables for Espinharas River sub-basin - PB/RN States   ABSTRACT: In the Brazilian semiarid, where the caatinga biome is inserted, precipitation is a limiting factor for its socioeconomic and environmental development, This study evaluated the correlation between the level of vegetation cover and the local rainfall variables, considering the climatology of 2005 and 2015, using images from the TM and OLI sensors of the Landsat 5 and Landsat 8 satellites, respectively. The year 2005 presented higher NDVI values compared to 2015, with maximum values of 0.71 and 0.78 in the dry and wet periods, respectively. In 2015, the maximum values are 0.64 and 0.61, for the dry and wet periods, respectively. The highest values were observed in the rainy period of 2005, in the weather stations of Matureia, Salgadinho and Areia de Baraúnas. In the dry period, the low variability of NDVI values is noted, with the highest readings observed in the Matureia, Salgadinho and Teixeira platforms. The platforms that showed the greatest reductions in NDVI values from 2005 to 2015, in the rainy season, were Matureia, Santa Teresinha and Salgadinho, with reductions of 41.9%, 38.2% and 32.7%, respectively. The most significant correlations were established for the dry periods. The smallest correlations were found in the rainy season. The increase in rainfall levels in the region did not imply a progressive increase in NDVI values. Keywords: semiarid; geoprocessing; normalized difference vegetation index.


Author(s):  
Jesús Enrique Chavarría Párraga ◽  
Julio Cesar Ramírez-Caicedo ◽  
Jorge Isaac Zambrano-Kuffó ◽  
Richard Xavier Bravo-Ferrín ◽  
Luis Enrique Párraga-Muñoz

Coefficient of Vigna unguiculata L. Walp. for dry and rainy periods in the Chone river valley Resumen El uso del agua en la agricultura es una actividad muy demandante a nivel mundial, por ello es necesario conocer la cantidad de agua que consumen los vegetales de interés agrícola. Se investigó el coeficiente del cultivo (Kc) de Vigna unguiculata L. Walp. (cv. INIAP-463) para periodos secos y lluviosos de Chone, Manabí, Ecuador a través de lisimetría de drenaje. Se ejecutó en el año 2019, implementándose tres lisímetros de drenaje cerca de la estación climatológica M0162. La lámina de riego fue aplicada en base a la evapotranspiración de referencia diaria (ETo). Se realizó el cálculo del Kc para cada etapa fenológica del cultivo determinando el cociente entre la evapotranspiración del cultivo (ETc) y ETo. El frejol presentó cuatro etapas según su consumo hídrico, reportando valores de Kc de 0,55; 0,92; 1,30 y 0,80 para el periodo seco y 0,45; 0,88; 1,28 y 0,75 para el periodo lluvioso. Las necesidades hídricas del frejol fueron 219,37 mm para el período seco y 237,82 mm para el período lluvioso durante 85 días que duró el ciclo del cultivo. Los valores de Kc y necesidades hídricas varían según las condiciones climáticas de las zonas en donde se desarrollen los cultivos. Palabras clave: evapotranspiración; lámina de drenaje; necesidades hídricas; riego; leguminosa. Abstract Water use in agriculture is a very demanding activity worldwide, therefore it is necessary to know the amount of water consumed by vegetables of agricultural interest. The crop coefficients (Kc) of Vigna unguiculata L. Walp was investigated. (cv. INIAP-463) for dry and rainy periods of Chone, Manabí, Ecuador through drainage lysymmetry. It was executed in 2019, implementing three drainage lysimeters near the M0162 weather station. The irrigation sheet was applied based on the daily reference evapotranspiration (ETo). Kc was calculated for each phenological stage of the crop by determining the quotient between the evapotranspiration of the crop (ETc) and ETo. The bean presented four stages according to its water consumption, reporting Kc values ​​of 0.55; 0.92; 1.30 and 0.80 for the dry period and 0.45; 0.88; 1.28 and 0.75 for the rainy season. The water needs of the beans were 219.37 mm for the dry period and 237.82 mm for the rainy period during the 85 days of the crop cycle. The Kc values ​​and water needs vary according to the climatic conditions of the areas where the crops are grown. Keywords: evapotranspiration; drainage sheet; irrigation; water needs; legume.


2016 ◽  
Vol 77 (3) ◽  
pp. 495-505 ◽  
Author(s):  
R. S. Cordeiro ◽  
J. E. L. Barbosa ◽  
G. Q. Lima Filho ◽  
L. G. Barbosa

Abstract The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates.


2007 ◽  
Vol 21 (3) ◽  
pp. 641-648 ◽  
Author(s):  
Ariadne do Nascimento Moura ◽  
Maria do Carmo Bittencourt-Oliveira ◽  
Ênio Wocyli Dantas ◽  
João Dias de Toledo Arruda Neto

The aim of this study was to characterize phytoplankton associations, as well as discuss controlling factors determining algal dominance in a eutrophic tropical reservoir, Mundaú, Pernambuco, Brazil. Water samples were collected during the dry period (January/2005) and the rainy period (June/2005). The samples were collected from both limnetic and littoral regions, and the phytoplankton assemblages identified from current literature after preservation in formaldehyde 4%. At the same time as sampling was done, in situ measurements of water temperature, transparency, dissolved oxygen, and pH were also taken. Total phosphorus, total nitrogen concentration and the Trophic State Index were subsequently determined in the laboratory. Phytoplankton density (ind. L-1) was estimated using an inverted Zeiss microscope. Grouping of the phytoplankton associations was carried out using the Reynolds phytosociological classification. During the dry period, reservoir water showed low dissolved oxygen concentrations, alkaline pH and was relatively turbid compared to the situation during the rainy season. Reservoir water is limited by nitrogen during both seasonal periods. The Trophic State Index is classified as determining eutrophic conditions. Phytoplankton was represented by 70 infrageneric taxa grouped in 16 functional associations, with the majority typical of eutrophic systems. This fact is supported by quantitative analysis, which shows the dominance of S associations comprising exclusively R-strategist cyanobacteria.


2005 ◽  
Vol 48 (6) ◽  
pp. 983-996 ◽  
Author(s):  
Michael Goulart ◽  
Marcos Callisto

The objectives of this study were to evaluate spatial and seasonal distribution, assemblage structure and substrate associations of mayfly nymphs in five lotic ecosystems in the headwaters of the Doce River and São Francisco River watersheds, Brazil. Samples were taken in 24 sampling stations during rainy and dry seasons in 1998. In total, 7,066 organisms were collected, belonging to 27 genera and 6 families of Ephemeroptera. The dominant taxa were Americabaetis, Paracloeodes, Leptohyphes and Hagenulus. During the rainy period, the São Francisco River watershed showed higher taxonomic richness, diversity and evenness, while in the dry period, the taxonomic richness was higher in Doce River watershed. No significant differences were found in the taxonomic richness, diversity, evenness and density of mayfly assemblages between the two studied sampling periods. The results suggested that the diversity of the mayfly assemblages in tropical headwaters of Serra do Cipó would be probably due to ecosystem and watershed characteristics.


Author(s):  
Gustavo H. da Silva ◽  
Santos H. B. Dias ◽  
Lucas B. Ferreira ◽  
Jannaylton É. O. Santos ◽  
Fernando F. da Cunha

ABSTRACT FAO Penman-Monteith (FO-PM) is considered the standard method for the estimation of reference evapotranspiration (ET0) but requires various meteorological data, which are often not available. The objective of this work was to evaluate the performance of the FAO-PM method with limited meteorological data and other methods as alternatives to estimate ET0 in Jaíba-MG. The study used daily meteorological data from 2007 to 2016 of the National Institute of Meteorology’s station. Daily ET0 values were randomized, and 70% of these were used to determine the calibration parameters of the ET0 for the equations of each method under study. The remaining data were used to test the calibration against the standard method. Performance evaluation was based on Willmott’s index of agreement, confidence coefficient and root-mean-square error. When one meteorological variable was missing, either solar radiation, relative air humidity or wind speed, or in the simultaneous absence of wind speed and relative air humidity, the FAO-PM method showed the best performances and, therefore, was recommended for Jaíba. The FAO-PM method with two missing variables, one of them being solar radiation, showed intermediate performance. Methods that used only air temperature data are not recommended for the region.


Irriga ◽  
2005 ◽  
Vol 10 (3) ◽  
pp. 215-228 ◽  
Author(s):  
José Eduardo Pitelli Turco ◽  
Manoel Teixeira de Faria ◽  
Edemo João Fernandes

INFLUÊNCIA DA FORMA DE OBTENÇÃO DO SALDO DE RADIAÇÃO NA COMPARAÇÃO DE MÉTODOS DE ESTIMATIVA DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA  José Eduardo Pitelli Turco; Manoel Teixeira de Faria; Edemo João FernandesDepartamento de Engenharia Rural, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista,  Câmpus de Jaboticabal, Jaboticabal , SP, [email protected]    1        RESUMO Uma maneira freqüentemente utilizada para verificar a eficiência de métodos de estimativa da  evapotranspiração de referência (ETo) em diferentes situações e locais é por meio de comparação com um método padrão. Porém, a utilização de diferentes métodos para a obtenção do saldo de radiação, empregado na estimativa da evapotranspiração, pode conduzir a resultados distintos. O objetivo desse trabalho foi avaliar a influência do método de obtenção do saldo de radiação na comparação de quatro métodos (FAO-Tanque Classe A, FAO-Radiação Solar, Makkink e Hargreaves-Samani) com o método padrão recomendado pela FAO (Penman-Monteith). A pesquisa foi desenvolvida em área experimental do Departamento de Engenharia Rural da FCAV/UNESP, Campus de Jaboticabal, SP, onde foi instalada uma estação meteorológica automatizada e um Tanque Classe A. Por intermédio de um sistema de aquisição de dados foram obtidas medidas da radiação solar global, saldo de radiação, temperatura do ar,  umidade relativa do ar e velocidade do vento. Os resultados indicam que as formas de obtenção do saldo de radiação podem alterar  a estimativa da evapotranspiração diária obtida pelo método de Penman-Monteith.  UNITERMOS: estação meteorológica automatizada, radiação solar, Penman-Monteith  TURCO, J. E. P.; FARIA, M. T. de; FERNANDES E. J. INFLUENCE  OF  NET RADIATION OBTENTION METHOD COMPARED TO  THE  REFERENCE  EVAPOTRANSPIRATION ESTIMATE METHODS  2        ABSTRACT One way to verify the efficiency of evapotranspiration reference (ETo) estimate methods in different conditions is through the comparison to a standard method. However the utilization of several methods to obtain the net radiation using evapotranspiration reference  estimate, can end up in different results. The purpose of this paper was to evaluate the influence of the net radiation obtention method compared to four methods (FAO – Class A pan, FAO – Radiation, Makkink and Hargreaves-Samani) to the Penman-Montheith method which is considered a standard method by FAO. The research was carried out at an experimental area of the Rural Engineering Department of FCAV/São Paulo State University,  Jaboticabal, SP, Brazil. Global net radiation, air temperature, air relative humidity, and  wind speed were obtained using an automated weather station equipped with sensors. The results showed that the net radiation obtaintion methods can alter the daily evapotranspiration estimate obtained by the Penman-Montheith method. KEYWORDS:  automated  weather station, solar radiation, Penman-Monteith


DYNA ◽  
2021 ◽  
Vol 88 (216) ◽  
pp. 176-183
Author(s):  
Iug Lopes ◽  
Miguel Julio Machado Guimarães ◽  
Juliana Maria Medrado de Melo ◽  
Ceres Duarte Guedes Cabral de Almeida ◽  
Breno Lopes ◽  
...  

The objective was to perform a comparative study of the meteorological elements data that most cause changes in the reference Evapotranspiration (ETo, mm) and its own value, of automatic weather stations AWS and conventional weather stations CWS of the Sertão and Agreste regions of Pernambuco State. The ETo was calculated on a daily scale using the standard method proposed by the Food and Agriculture Organization (FAO), Penman-Monteith (FAO-56). The ETo information obtained from AWS data can be used to update the weather database of stations, since there is a good relationship between the ETo data obtained from CWS and AWS, statistically determined by the Willmott's concordance index (d > 0.7). The observed variations in the weather elements: air temperature, relative humidity, wind speed, and global solar radiation have not caused significant changes in the ETo calculation.


2008 ◽  
Vol 82 (2) ◽  
pp. 113-118 ◽  
Author(s):  
B.V. Maikai ◽  
J.U. Umoh ◽  
O.J. Ajanusi ◽  
I. Ajogi

AbstractEnvironmental and socio-cultural variables influencing the distribution of helminth eggs in 608 soil samples were studied in 14 playgrounds that differ in socio-economic status in Kaduna metropolis, Nigeria, using a modified sieving method and a sucrose flotation medium of specific gravity 1.27. Helminth eggs were found in 62% of the soil samples and the distribution was as follows: Toxocara spp. 50.4%, Taenia spp./Echinococcus spp. 36.9%, Dipylidium caninum 26.3%, Ancylostoma spp. 9.0%, Ascaris spp. 7.2%, Trichuris spp. 3.7% and Ascaridia spp. 1.9%. A higher prevalence (68.1%) was recorded during the dry harmattan period while in the rainy period the rate was 58.1%. Mean egg densities ranged from 1.11 ± 0.32 to 3.92 ± 2.47 in areas moderately rated. Samples from site 14, which was highly rated, were more contaminated (78.1%) than those collected from other sites, while the intensity of contamination (14.0%) was more in moderately rated site 4 than in the rest of the sites. There were significant associations between the prevalence of helminth eggs and rainy period of the study (odds ratio (OR) = 0.38; 95% confidence interval (CI) on OR: 0.20 < OR < 0.70), presence of dogs (OR = 0.56; 95% CI on OR: 0.37 < OR < 0.85) and grass (vegetation) (OR = 1.44; 95% CI on OR: 1.03 < OR < 2.04) in the sites. On the other hand, there was no association between the prevalence of helminth eggs and the dry period of the study, presence of refuse in the playgrounds, topography of playgrounds, depth of sample collection and socio-economic status of people in playgrounds (P>0.05). This study shows that the period of study, the presence of dogs and vegetation influence the prevalence of helminth eggs in soil in Kaduna metropolis.


Sign in / Sign up

Export Citation Format

Share Document