scholarly journals Class A pan coefficients (Kp) to estimate daily reference evapotranspiration (ETo)

2003 ◽  
Vol 7 (1) ◽  
pp. 111-115 ◽  
Author(s):  
Paulo C. Sentelhas ◽  
Marcos V. Folegatti
Keyword(s):  
High Efficiency ◽  
Reference Evapotranspiration ◽  
Climatic Conditions ◽  
High Dispersion ◽  
Pan Evaporation ◽  
Class A ◽  
Irrigated Crops ◽  
Precision And Accuracy ◽  
The Relationship ◽  
Class A Pan

The class A pan coefficient (Kp) has been used to convert pan evaporation (ECA) to grass-reference evapotranspiration (ETo), an important component in water management of irrigated crops. There are several methods to determine Kp values, using wind speed, relative humidity and fetch length and conditions. This paper analyses the following methods to estimate Kp values: Doorenbos & Pruitt (1977); Cuenca (1989); Snyder (1992); Pereira et al. (1995); Raghuwanshi & Wallender (1998); and FAO/56 (Allen et al., 1998). The estimated values of Kp and the observed Kp, obtained from the relationship between ETo measured in a weighing lysimeter and ECA measured in a class A pan, were compared by regression analysis. The same routine was adopted to evaluate ETo estimates with the different Kp values. The results showed that all methods to estimate Kp did not predict it well, with low correlation (R²< 0.2), which resulted in estimates of ETo with high dispersion (R²< 0.8). The best Kp methods to estimate ETo were Pereira et al. (1995) and Cuenca (1989), both presenting high efficiency. The use of an arbitrary and constant Kp (0.71) to estimate ETo, produced the same precision and accuracy as the estimates of Kp based on Pereira and Cuenca methods. This fixed value is a practical and simple option to convert ECA into ETo, but this value must be calibrated for each place under different climatic conditions.

scholarly journals Reference evapotranspiration based on class A pan evaporation

2002 ◽  
Vol 59 (3) ◽  
pp. 417-420 ◽  
Author(s):  
Marco Antônio Fonseca Conceição
Keyword(s):  
Reference Evapotranspiration ◽  
Regression Coefficients ◽  
Pan Evaporation ◽  
Annual Average ◽  
Paulo State ◽  
Class A ◽  
Best Value ◽  
Pan Coefficient ◽  
Northwest Region ◽  
Class A Pan

Estimating reference evapotranspiration (ETo) based on Class A pan evaporation (ECA) is very usual in irrigated areas. For this purpose the ECA values are multiplied by a pan coefficient (Kp) to obtain ETo. Kp values can be estimated in different ways being, however, important to know which method would estimate the best value for a given locality. In the present work estimated values of ETo based on Class A pan evaporation, using Kp values determined by different methods, were compared to Penman-Monteith-FAO (EToPM) values for the northwest region of the São Paulo State, Brazil. The annual average Kp, determined dividing EToPM by ECA, was 0.74. For the rainy months (December to March) the average Kp value was 0.80 and for the dry months (April to November) 0.70. The reference evapotranspiration estimated using Kp determined by the Snyder equation presented the best regression coefficients when compared to EToPM.

scholarly journals Evaluation of Reference Evapotranspiration Equations under Current Climate Conditions of Egypt

2015 ◽  
Vol 3 (10) ◽  
pp. 819
Author(s):  
Gamal El Afandi ◽  
Mohamed Abdrabbo
Keyword(s):  
Nile Delta ◽  
Reference Evapotranspiration ◽  
Climatic Conditions ◽  
P Value ◽  
Climate Conditions ◽  
Climatic Regions ◽  
Class A ◽  
The North ◽  
The Difference ◽  
Class A Pan

Precise estimation of the reference evapotranspiration is very important and vital in different fields such as agriculture, hydrology and meteorology. The aim of the current study was to evaluate the performance of different reference evapotranspiration methods compared to Class-A pan or E-pan over different agro-climatic regions in Egypt. In this study, Egypt has divided into several agro-climatic regions according to the average air temperature and the reference evapotranspiration from Class-A pan. These were Nile Delta in the north, middle and Upper Egypt. Four reference evapotranspiration (ETo) methods namely; Blaney-Criddle, Hargreaves, Thornthwaite and FAO-56 Penman-Monteith (PM) have been evaluated in this study. The results revealed that, there were statistically no significance between E-Pan and PM at P-value less than 0.05, while the other equations had significant differences. The Hargreaves equation reported the highest ETo value at all regions while Thornthwaite was the lowest one. The difference percentage ratios between FAO-56 Penman-Monteith, Blaney-Criddle, Thornthwaite and Hargreaves and E-Pan were 3.7, -13.3, -24.8 and 10.7 respectively. Hence, FAO-56 Penman-Monteith method has proved its capability in estimation of reference evapotranspiration over different agro-climatic regions in Egypt. Therefore, it could be used over any region in Egypt especially those have no reference evapotranspiration instruments.This study is a regional research, similar studies has been made for different regions by many researchers. Therefore, the determined results in this study can be used for regions with similar climatic conditions.

scholarly journals EVAPOPLUVIÔMETRO: NOVO SISTEMA DE MEDIDA DA EVAPORAÇÃO EM TANQUE CLASSE A

Irriga ◽  
2005 ◽  
Vol 10 (1) ◽  
pp. 76-81
Author(s):  
Nilson Augusto Villa Nova ◽  
Paulo Cesar Sentelhas ◽  
Andre Belmont Pereira
Keyword(s):  
Water Management ◽  
Free Surface ◽  
Data Collection ◽  
Current System ◽  
Irrigation Management ◽  
Climatic Conditions ◽  
Pan Evaporation ◽  
Class A ◽  
Class A Pan ◽  
New System

EVAPOPLUVIÔMETRO: NOVO SISTEMA DE MEDIDA DA EVAPORAÇÃO EM TANQUE CLASSE A  Nilson Augusto Villa Nova1; Paulo César Sentelhas2; André Belmont Pereira31 Pesquisador Científico 1-A do CNPq – [email protected] Departamento de Ciências Exatas, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Cx. Postal 9, CEP 13418-900 - Piracicaba, SP3Departamento de Ciência do Solo e Engenharia Agrícola, Universidade Estadual de Ponta Grossa, Campus de Uvaranas, CEP 84030-900 - Ponta Grossa, PR  1 RESUMO             Um novo sistema de medidas acoplado a um tanque classe A padrão, que efetua um balanço entre a evaporação de uma superfície livre de água exposta às condições meteorológicas reinantes e a precipitação pluvial, é proposto neste estudo. A vantagem do presente sistema é que o mesmo dispensa a utilização de uma válvula reguladora do nível de água no interior do tanque medidor na avaliação do processo de perda d'água para a atmosfera, e considerando que o tanque medidor proposto é também um pluviômetro, infere-se que o sistema em estudo permite a coleta de dados para dias com chuvas leves (intensidade com ordem de grandeza da evapotranspiração), melhorando, portanto, a confiabilidade das leituras obtidas com o tanque classe A padrão empregado largamente no manejo de água das culturas. UNITERMOS: tanque classe A, evapotranspiração, manejo da irrigação.  VILLA NOVA, N.A.; SENTELHAS, P.C.; PEREIRA, A.B.EVAPO-PLUVIOMETER: A NEW SYSTEM FOR MEASURING THE CLASS A  PAN EVAPORATION  2 ABSTRACT             A new system of measurements coupled to a standard class A pan that may balance evaporations of a water free surface exposed to the local climatic conditions and to rainfall is proposed. The advantage of the current system is that it deals with a system that allows data collection on days light rainfall days (i.e. when rainfall intensities correspond to evapotranspiration), once it does not require a valve for water level regulation inside the measurer tank to assess water loss into the atmosphere, and because this proposed measurer tank is also a pluviometer. Thus, the reliability of the readings obtained by the conventional class A pan within water management on crops is improved. KEYWORDS: class A pan, evapotranspiration, irrigation management.

scholarly journals 686 PB 230 RESEARCH AND DEVELOPMENT OF A MINIATURE PAN EVAPORIMETER FOR GAUGING THE DIFFERENCE BETWEEN EVAPOTRANSPIRATION AND EFFECTIVE RAINFALL

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 531b-531
Author(s):  
Christopher L. Browne ◽  
Thomas W. Cook
Keyword(s):  
Pacific Northwest ◽  
Reference Evapotranspiration ◽  
Effective Rainfall ◽  
Pan Evaporation ◽  
Irrigation Requirement ◽  
Class A ◽  
The Pacific ◽  
Pan Coefficient ◽  
The Difference ◽  
Class A Pan

Knowledge of the current irrigation requirement of well-watered grass provides the basis for efficient scheduling of turf and landscape irrigation. A portable, miniature pan evaporimeter has been developed to conveniently provide this information for localized micro-climates. The underlying equation for the instrument is: IRnet = (Kpan • Epan - Kpan • R) where IRnet is the net irrigation requirement of healthy, non-stressed grass; Kpan is the pan coefficient for the instrument; Epan is accumulative pan evaporation; Kpan • Epan is “reference evapotranspiration”; and Kpan • R is a measure of effective rainfall received. This equation was established using turfgrass sites located throughout the Pacific Northwest over a 3-year period. The sites were in proximity to U.S. Class “A” pan evaporimeters, and were automatically irrigated using moisture sensors. Tests of the miniature evaporimeter against automated meteorological stations have determined the factors that influence its pan coefficient, and therefore its ultimate design.

RATIO BETWEEN EVAPOTRANSPIRATION OF IRRIGATED CROPS FROM FLOATING LYSIMETERS AND CLASS A PAN EVAPORATION

1980 ◽  
Vol 60 (1) ◽  
pp. 197-201 ◽  
Author(s):  
C. S. TAN ◽  
J. M. FULTON
Keyword(s):  
Sandy Loam ◽  
Crop Coefficient ◽  
Pan Evaporation ◽  
Crop Evapotranspiration ◽  
Late Season ◽  
Class A ◽  
Maximum Value ◽  
Irrigated Crops ◽  
Class A Pan ◽  
Processing Tomatoes

The crop coefficient (Kc), the ratio of crop evapotranspiration (ET) to potential or maximum evapotranspiration (ETo) was determined for early potatoes, corn and processing tomatoes grown on Fox sandy loam near Harrow, Ontario. ET was measured with floating lysimeters and ETo with Class A pan. The value of Kc depends on the percentage of foliage cover on the soil, increasing from emergence to approximately 50–80% of foliage cover, remains at a maximum value for about 2–5 wk, and thereafter decreases during the late season stage until the crops approach maturity.

DISTRIBUIÇÃO DA EVAPORAÇÃO EM ESTUFA PLÁSTICA NA PRIMAVERA

Irriga ◽  
2001 ◽  
Vol 6 (3) ◽  
pp. 120-127
Author(s):  
Reginaldo Ferreira Santos ◽  
Antonio Evaldo Klar
Keyword(s):  
Spatial Variability ◽  
Pan Evaporation ◽  
Spring Season ◽  
Class A ◽  
Agricultural Sciences ◽  
E Mail ◽  
Center Area ◽  
Class A Pan

DISTRIBUIÇÃO DA EVAPORAÇÃO EM ESTUFA PLÁSTICA NA PRIMAVERA  Reginaldo Ferreira SantosCentro de Ciências Exatas e Tecnológica da UNIOESTE- CP 711CEP 858114-110, Cascavel, PR - Fone: 0XX45 2203155.  E-mail: [email protected] Evaldo KlarDepartamento de Engenharia Rural - Faculdade de Ciências Agronômica- UNESP - CEP 18603-970 - Botucatu, SP. CP: 237.  E-mail:  [email protected]  1  RESUMO O presente trabalho teve como objetivo avaliar a distribuição da evaporação no interior de uma estufa plástica, com uma cultura de pimentão, através da variabilidade espacial e comparar a evaporação dos microevaporímetros com os valores do Tanque classe "A". O experimento foi conduzido no Campus da Universidade Estadual Paulista - FCA/UNESP, no período de primavera, em estufa plástica de polietileno de baixa densidade (PEBD). Na distribuição da evaporação em estufa com orientação norte/sul, verificou-se que as maiores evaporações ocorreram nas extremidades sul e norte tendente ao lado oeste. Já as menores evaporações localizaram-se no centro. No período de primavera, a evaporação média nos microevaporímetros superestimou em 55% a evaporação determinada no Tanque classe "A". UNITERMOS: evaporação, geoestatística, estufa.  SANTOS, R.F, KLAR, A.E.  EVAPORATION DISTRIBUTION INSIDE A PLASTIC TUNNEL IN THE SPRING SEASON  2  ABSTRACT                 The main aim of this study was to verify the evaporation distribution inside a plastic tunnel, with pepper crop, oriented to north/south, through spatial variability and to compare Class A Pan evaporation to punctual evaporations of 40 equidistant microevaporimeters placed from 50cm the soil. The study was carried out at the College of Agricultural Sciences/UNESP, Botucatu – SP in the spring season.  The highest evaporation occurred next to north and to south sides of the tunnel, with tendency to west. Consequently, the lowest evaporations occurred at the center area. The microevaporimeter evaporations were 55% higher than those obtained from Class A Pan. KEYWORDS: evaporation distribution, microevaporimeter.

scholarly journals Annual Actual Evapotranspiration Estimation via GIS Models of Three Empirical Methods Employing Remotely Sensed Data for the Peloponnese, Greece, and Comparison with Annual MODIS ET and Pan Evaporation Measurements

2021 ◽  
Vol 10 (8) ◽  
pp. 522
Author(s):  
Stavroula Dimitriadou ◽  
Konstantinos G. Nikolakopoulos
Keyword(s):  
Time Scale ◽  
Gradual Decrease ◽  
Actual Evapotranspiration ◽  
Pan Evaporation ◽  
Empirical Methods ◽  
Remotely Sensed Data ◽  
Upward Trend ◽  
Class A ◽  
Evapotranspiration Estimation ◽  
Class A Pan

Actual evapotranspiration (ETa) has been insufficiently investigated in Greece. This study aimed to estimate annual ETa by empirical methods (Turc, modified Turc, and Coutagne) for the Peloponnese, Greece, a Mediterranean testbed, between 2016–2019, four of the warmest years since the preindustrial era, and compare them to MODIS ET. Furthermore, measurements of annual pan evaporation (Epan) were performed for two Class A pan stations in the Peloponnese with different reliefs and conditions. The empirical methods and statistical formulae (RMSD, MB, and NMB) were developed as models in ArcMap. The outcomes of the Turc method resembled MODIS ET ranges for all years, followed by those of Coutagne. The estimates by the modified Turc method were almost identical to MODIS ET. Therefore, the modified Turc method can be used as an alternative to MODIS ET (and vice versa) for the Peloponnese for 2016–2019. Moreover, the Epan at Patras University station (semiurban, low elevation) exhibited an upward trend resembling the trends of the empirical methods over the study years, whereas the Epan at Ladonas station (higher elevation, lakeside) required investigation on a monthly time scale. Additionally, the gradual decrease of pan-water icing at Ladonas in December (from 20 d in 2016 to 0 d in 2019) could imply an undergoing decrease in snowpack storage retention across the mountains of the Peloponnese.

scholarly journals WATER USE BY BROCCOLI PLANTS (Brassica oleracea F, var. Italica)

Irriga ◽  
2003 ◽  
Vol 8 (1) ◽  
pp. 37-43
Author(s):  
Antonio Evaldo Klar ◽  
Ed Wilson Da Silva Fontes
Keyword(s):  
Water Level ◽  
Brassica Oleracea ◽  
Water Use ◽  
Water Table ◽  
Reference Evapotranspiration ◽  
Crop Coefficient ◽  
Paspalum Notatum ◽  
Agricultural Engineering ◽  
Class A ◽  
Class A Pan

WATER USE BY BROCCOLI PLANTS (Brassica oleracea F, var. Italica)  Antonio Evaldo Klar* Ed Wilson da Silva FontesDepartment of Agricultural Engineering, College of Agricultural Sciences, State University of São Paulo, P.O. 237, CEP 18603-970, Botucatu – SP. E-mail: [email protected]* Scientific Researchist of CNPq.  1 ABSTRACT  Broccoli (Brassica oleracea F, var. Italica) plants were transplanted to four lysimeters (116 cm x 116 cm and 150 cm depth), two of them maintained at 40 cm and two at 50 cm water table.  Other two lysimeters, one for each level, received grass (Paspalum notatum, F.) to measure Reference Evapotranspiration (EToLY). Surrounded area received 2,500 m2 of broccoli plants with soil water potentials ( s) maintained higher than –30 kPa. The results allowed to conclude: - there were no statistical differences between the plant parameters from 40cm lysimeters and the surrounded area; - the Class A Pan, Radiation-FAO, Penman-FAO and Penman-Monteith Reference Evapotranspiration (ETo) methods, in this order, had significant correlations to the data obtained from 40 cm water table level lysimeter; - the Kc (crop coefficient) broccoli values ranged from 0.88 to 1.42 for KcLY (Lysimeters), 1.24 to 2.14 for KcA (Class A Pan), 1.19 to 1.71 for KcPM (Penman-Monteith), 0.95 to1.42 for KcPF (Penman-FAO) and 0.82 to 1.49 for KcR (Radiation-FAO) from stages II to V; - the plant water using ranged from 4.09 to 6.25 mm/day for 40 cm water level, and 2.68 to 5.25 mm/day for 50 cm water level for the same stages, respectively. The lysimeters at 50 cm water level yielded 64,3% less inflorescences and 8.1% lower water using efficiency than the plants from 40 cm water level lysimeters.  KEY WORDS: irrigation, evapotranspiration, broccoli.  KLAR, A.E.; FONTES, E.W.S. USO D’ÁGUA POR PLANTAS DE BRÓCOLOS (Brassicaoleracea F, var. Itálica).  2 RESUMO  Plantas de brócolos foram transplantadas para 4 lisímetros de 116 x 116 de área x 150 cm de profundidade, sendo dois mantidos com 40 cm e outros dois com 50 cm de nível de lençol freático. Outros dois lisímetros foram usados para medir a evapotranspiração de referência (EToLy) com grama batatais nos mesmos níveis de água. Os lisímetros foram colocados no meio de uma cultura de brócolos com área de 2500 m2, com o potencial de água do solo mantido acima de –30kPa. Os resultados permitiram que se concluísse: - não houve diferenças estatisticamente significativas entre os valores de área foliar, pesos de matéria seca das folhas e das inflorescências entre as plantas de fora e de dentro dos lisímetros de nível de água de 40 cm; - os métodos do tanque Classe A, FAO-Radiação, Penman-FAO e Penman-Monteith, nesta ordem, correlacionaram-se significativamente com os dados obtidos no lisímetro de grama de nível 40 cm; - os lisímetros com brócolos e nível de 50 cm tiveram produtividade 64,3% menor e mostraram eficiência de uso de água 8,1% menor que os de 40 cm e 2,68 a 5,25 mm de evapotranspiração por dia, não sendo, portanto, indicados para a medir-se EToLY;- os valores dos coeficientes de cultura variaram de 0,88 a 1,42 para KcLY (lisímetro de 40 cm), de 1,24 a 2,14 para KcA (tanque Classe A), de 1,19 a 1,71 para KcPM (Penman-Monteith), de 0,95 a 1,42 para KcPF (Penman-FAO) e de 0,82 a 1,49 para KcR (FAO-Radiação) para os estádios II a V, respectivamente.  UNITERMOS: brócolos, coeficiente de cultura, evapotranspiração de referência.

Sign in / Sign up

Export Citation Format

Share Document