Assessment of Hargreaves Equation for Estimating Monthly Reference Evapotranspiration in the South of Iran

Evapotranspiration is one of the most important components of the hydrological cycle. Evapotranspiration (ETo) is an important variable in water and energy balances on the earth’s surface, and knowledge of the distribution of ET is a key factor in hydrology, climatology, agronomy and ecology studies. Many researchers have a valid relationship, which is a function of climate factors, to estimate the potential evapotranspiration presented to the plant water stress or water loss, prevent. The FAO-Penman method (PM) had been recommended as a standard method. This method requires many data and these data are not available in every area of world. So, other methods should be evaluated for these conditions. When sufficient or reliable data to solve the PM equation are not available then Hargreaves equation can be used. The Hargreaves equation (HG) requires only daily mean, maximum and minimum air temperature extraterrestrial radiation .In this study, Hargreaves method (HG) were evaluated in 12 stations in the North West region of Iran. Results of HG and M.HG methods were compared with results of PM method. Statistical analysis of this comparison showed that calibration process has had significant effect on efficiency of Hargreaves method.

Authors:

• Ali Dehgan Moroozeh
• B. Farhadi Bansouleh

Keywords:

• Evapotranspiration
• Hargreaves equation
• FAOPenman method.

References:

[1] Allen, R. G., Pereira, L.S., Reas, D., and Smith, M. (1998). “Crop
Evapotranspiration.” FAO Irrigation and Drainage Paper 56, Rome, 300. [2] Fooladmand, H. R., and Haghighat, M. (2007). “Spatial and temporal
calibration of Hargreaves equation for calculating monthly ETo based on
Penman-Monteith method.” Irrig. And Drain, 56, 439–449.
[3] Fooladmand, H.R., and Sepaskhah A. R. (2005). “Regional calibration
of Hargreaves equation in a semiarid region.” Iran-Water Recourses
Research, 1(2), 1-6. (In persion).
[4] Gavila´n, P., Lorite, I.J., Tornero, S., Berengena, J. (2006). “Regional
calibration of Hargreaves equation for estimating reference ET in a
semiarid environment.” Agric. Water Manag., 81(3), 257–281.
[5] Hargreaves, G. H., and Samani, Z. A. (1985). “Reference crop
evapotranspiration from ambient air temperature”, Paper No. 85-2517.
American society of agricultural engineers. Chicago, IL.
[6] Hargreaves, G. H., and Allen, R. G. (2003). “History and evaluation of
Hargreaves evapotranspiration equation.” J. Irrig. Drain. Eng., 129(1),
53-63.
[7] Jabloun, M., and Sahli, A. (2008). “Evaluation of FAO-56 methodology
for estimating reference evapotranspiration using limited climatic data
Application to Tunisia.” Agric. Water Manag., 95(6), 707 – 715.
[8] Martinez-Cob, A. and Tejero-Juste, M. (2004). “A wind-based
qualitative calibration of the Hargreaves ETo estimation equation in
semiarid regions.” Agric. Water Manag., 64(3), 251–264.
[9] Noori Mohammadieh, M., Mohammadi, M., Helali, J., Nazari, B., and
Sohrabi, T. (2009). “Evaluation of Hargreaves equation for calculating
daily ETo (Case study: North West of Iran)”. Advances in Natural and
Applied Sciences, 3(2), 273-278.
[10] Rahimi Khoob, A. (2008). “Comparative study of Hargreaves’s and
artificial neural network’s methodologies in estimating reference
evapotranspiration in a semiarid environment.” Irrig. Sci., 26, 253-259.
[11] Sabziparvar, A. A., and Tabari, H. (2010). “Regional Estimation of
Reference Evapotranspiration in Arid and Semiarid Regions.” J. Irrig.
Drain. Eng., 136(10), 724–731.
[12] Salako, F. K. (2008). “Estimation of Evapotranspiration with FAO-56
Penman-Monteith equation for three Agroecological zones of Nigeria.”
ASSET, an International Journal, 8(2), 134-149.
[13] Sentelhas, P. C., Gillespie, T. J., and Santos, E. A. (2010). “Evaluation
of FAO Penman –Monteith and alternative methods for estimating
reference evapotranspiration with missing data in Southern Ontario,
Canada.” Agric. Water Manag., 97(5), 635–644.
[14] De Martonne, Emmanuel. 1926. A~"me et lnc:Uce artldite. Comptel
Rendus de L'Acad. BeL, Paris 182: 1396-1398.
[15] Rivas, R., & Caselles, V. (2004). A simplified equation to estimate
spatial reference evaporation from remote sensing-based surface
temperature and local meteorological data. Remote Sensing of
Environment, 83, 68−76
[16] Hofwegen van, P., Svensen, M., 2000. A Vision of Water for Food and
Rural Development. World Water Council (sector division documents)