Determination of Potential Evapotranspiration Using the Fuzzy Regression Method

Document Type : Original Article

Authors

1 Assistant Professor, Department of Irrigation, College of Agriculture, Shahrekord University, Shahrekord, Iran

2 Assistant Professor , Department of Natural resourses, College of Agriculture, Shahrekord University, Shahrekord, Iran.

3 Head of Planning Division, Water Resources Management Organization, Iran

Abstract

Potential evapotranspiration (ET0) rates are needed for irrigation scheduling. ET0 rates are commonly from weather parameters. The Penman-Monteith, is now accepted for computation of ET0. It requires several input parameters, some of which have no actual measurements but are estimated from measured weather parameters. In this study, the suitability of fuzzy regression was examined for estimating daily potential evapotranspiration with grass reference crop and compared with Artificial Neural Networks (ANN) and Penman-Monteith methods.The daily climatic data  of the Ekbatan station in Hamadan, including maximum and minimum temperature, maximum and minimum relative humidity, wind speed and sunny hours  are introduced as input data and ET0 as output data. ET0 values estimated from the fuzzy regression method were compared with direct ET0 measurements from lysimeters, and with ET0 estimations obtained using the Penman-Manteith equation and the ANN method. The estimated ET0 values from a fuzzy regression model using five input parameters, including maximum and minimum temperature, mean relative humidity, wind speed and sunny hours were obtained with RMSE=0.69mm/day, =0.88. The estimated ET0 values from a artificial neural networks model using the same input parameters were obtained with RMSE=0.74mm/day, =0.84. The estimated ET0 values from Penman-Monteith model  were obtained   with RMSE=1.21mm/day, =0.84. Thus, in this study the fuzzy regression is the best method.
 

Keywords

References

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Iran-Water Resources Research
Volume 3, Issue 3
June 2008
Pages 9-19

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History

  • Receive Date: 05 February 2007
  • Revise Date: 25 November 2007
  • Accept Date: 09 December 2007

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