M. Nazeer, H. Ali


Accurate and reliable potential evapotranspiration estimation depends on the method through which it is estimated. The aim of this research study is to compare and evaluate different potential evapotrasnpiration estimation methods against the standard FAO Penman -Monteith equation (FPM). The methods evaluated included simple Penman -Monteith equation (SPM), Hergreaves’s method (HM), Priestly Taylor method (PTM) and Makkink method (MM). Mean monthly data of all the climatic variables including maximum and minimum air temperature, relative humidity, wind speed, solar radiation and rainfall was recorded during 2010 from weather station installed inside the Agriculture Research Institute (ARI) Tarnab, Peshawar, Pakistan. Results revealed that all methods underestimated potential evapotranspiration value except the HM. A t and paired t-test was applied on overall means of the all methods and individually monthly means against FPM. There was no overall significant difference for all methods when compared against FPM annually. Significant differences were observed for all methods when subjected to paired t-test for individual monthly mean subjected against FPM. The SPM is considered best after FPM (R2 =0.99), but it also need high numbers of climatic parameters. While the HM which worked on only temperature variable and PT on solar radiation showed high correlation (R2 =0.98) with FPM. HM and PT are simpler and rely only on temperature and radiation data, can be used as an alternative to FPM if some of climatic data are missing or unreliable.

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J. Lu, Ge Sun, S. G. McNulty and D.M.

Amatya, J. Amer. Water Resources Assoc.

, No. 3 (2005) 621.

A. Baumgartner and E. Reichel. World Water

Balance: Mean Annual Global, Continental

and Maritime Precipitation, Evaporation and

Run-off. Elsevier, Amsterdam (1975) p. 179.

R.J.C. Burnash. The NWS river forecast

system catchments modeling. In: Singh, V.P.

(Ed.), Computer Models of Watershed

Hydrology. Water Resources Publications,

Highlands Ranch, CO (1995) pp. 311.

B.J. Choudhury and N.E. Di Girolamo,

Journal of Hydrology 205 (1998) 164.

G. Rasul and A. Mahmood, Pak. J. of [22]

Meteorology 5, No. 10 (2009) 12.

G.F. Makkink, J. Inst. Water Eng. 11, No. 3

(1957) 288.

G.H. Hargreaves and Z.A. Samani, Appl.

Engr. Agric. 1 (1985) 96.

R.G. Allen, L.S. Pereira, D. Raes and M.

Smith, Paper 56, Food and Agric. Orgn. of

the United Nations, Rome, Italy (1998) 300.

J. Doorenbos and W.O. Pruitt, Paper 24,

FAO, United Nations, Rome (1975) 115.

H.L Penman, Proc. Roy. Soc. London A193

(1948) 146.

H.A.R. De Bruin and J.N.M. Stricker, Hydrol.

Sci. 45, No. 3 (2000) 406.

M. Hussein and Al-Ghobari, Irrig. Sci. 19, No.


M. Nazeer, The Nucleus 47, No. 1 (2010) 41.

H.L Penman, The Physical Basis of Irrigation

Control. Rep. 13th Intl. Hort. Congr. 2 (1953)

p. 913-914.

W. Covey, Testing a Hypothesis Concerning

The Quantitative Dependence of

Evapotranspiration on Availability of Moisture.

Soil Physics, A. & M. College of Texas,

College Station, M.S. Thesis (1959) 58.

P.E. Rijtema, Analysis of Actual

Evapotranspiration. Agric. Res. Rep. No. 69,

Centre for Agric. Publ. and Doc.,

Wageningen (1965) 111.

J.L Monteith, Evaporation and Environment,

in G.E. Fogg (ed.) Symposium of the Society

for Experimental Biology, The State and

Movement of Water in Living Organisms

Academic Press, Inc., NY 19 (1965) pp. 205.

G.H. Hargreaves and Z.A. Samani, Appl.

Engr. Agric. 1 (1985) 96.

W.J Shuttleworth, Evaporation Models in

Hydrology. In: Schmugge, T.J., Andre´, J.C.

(Eds.), Land Surface Evaporation:

Measurement and Parameterization.

Springer, New York (1991) pp. 93.

C.H.B Priestley and R.J. Taylor, Monthly

Weather Review 100 (1972) 81.

G.F.J. Makkink, Institute of Water

Engineering 11 (1957) 277.

S. Er- RAK, G. Chehbouni, N. Guemouria,

J. Ezzahar, B. Duchemin, G.B Oulet,

R. Hadria1, A. Lakha, A. Chehbouni and J.C.

Rodriguez, Actes du Seminaire

Modernisation de l’Agriculture Irrigu´ee

Rabat, du 19 au 23 avril 2004.


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