COMPARISON OF DIFFERENT METHODS FOR ESTIMATION OF POTENTIAL EVAPOTRANSPIRATION

Authors

  • M. Nazeer Department of Water Management, NWFP Agriculture University, Peshawar, Pakistan

Abstract

Evapotranspiration can be estimated with different available methods. The aim of this research study to compare and evaluate the originally measured potential evapotranspiration from Class A pan with the Hargreaves equation, the Penman equation, the Penman-Montheith equation, and the FAO56 Penman-Monteith equation. The evaporation rate from pan recorded greater than stated methods. For each evapotranspiration method, results were compared against mean monthly potential evapotranspiration (PET) from Pan data according to FAO (ETo=Kpan×Epan), from daily measured recorded data of the twenty-five years (1984-2008). On the basis of statistical analysis between the pan data and the FAO56- Penman-Monteith method are not considered to be very significant ( =0.98) at 95% confidence and prediction intervals. All methods required accurate weather data for precise results, for the purpose of this study the past twenty five years data were analyzed and used including maximum and minimum air temperature, relative humidity, wind speed, sunshine duration and rainfall. Based on linear regression analysis results the FAO56 PMM ranked first ( =0.98) followed by Hergreaves method ( =0.96), Penman-Monteith method ( =0.94) and Penman method ( =0.93). Obviously, using FAO56 Penman Monteith method with precise climatic variables for ET 2 R 2 R 2 R 2 R 2 R o estimation is more reliable than the other alternative methods, Hergreaves is more simple and rely only on air temperatures data and can be used alternative of FAO56 Penman-Monteith method if other climatic data are missing or unreliable.

References

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

Amatya, Journal of the American Water

Resources Association 41, 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. 311-366.

B.J Choudhury and N.E DiGirolamo, Journal

of Hydrology 205 (1998) 164.

R.W.A Hutjes, P.Kabat, S.W. Running, W.J.

Shuttleworth and C.J Vorosmarty, Journal of

Hydrology 21, No.1 (1998) 212.

D.I. Stannard, Water Resources Research

, No. 5 (1993) 1379.

C.J. Vörösmarty, C.A. Federer and A.L. [22]

Schloss, J. Hydrol. 207 (1998) 147.

M. Nazeer, Journal of Agric. and Biol.

Sciences 4, No. 2 (2009) 68.

R.K Linsley, M.A Kohler and J.L Paulhus

Hydrology for Engineers, McGraw- Hill, New

York (1958) pp. 151-155.

R. Burman and L.O. Pochop, Evaporation,

Evapotranspiration and Climatic Data,

Elsevier Science, Amsterdam (1994) 600.

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.

Samani, J. Irrig. Drain. Eng. ASCE 126, No.

(2000) 265.

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

FAO, United Nations, Rome (1975) 115.

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. 93-120.

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

(1948) 120-146.

H.L Penman, The Physical Basis of Irrigation

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

-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)

P.E. Rijtema, Analysis of Actual Evapotranspiration. Agric. Res. Rep. No. 69, Centre for

Agric. Publ. and Doc., Wageningen (1965)

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 19

(1965) pp. 205-234. Academic Press, Inc.,

NY.

M.R. Raupach and J.J. Finnigan, Aust. J.

Plant Physiol 15 (1988) 706.

A.B. Pereira, N.A. Villa Nova and C.C Shock,

The Irrigation Association 25 (2004) p.325-39

Tampa Bay, Florida

Downloads

Published

10-03-2010

How to Cite

[1]
M. Nazeer, “COMPARISON OF DIFFERENT METHODS FOR ESTIMATION OF POTENTIAL EVAPOTRANSPIRATION”, The Nucleus, vol. 47, no. 1, pp. 41–46, Mar. 2010.

Issue

Section

Articles