Assessing reference evapotranspiration by the Hargreaves method in north-eastern Italy

The Food and Agriculture Organization of the United Nations proposed the (FAO)-56 Penman–Monteith equation (FAO-56 PM) as the standard method for estimating reference evapotranspiration (ET0). This equation requires weather data which are not available in most stations or present wide gaps and/or inaccuracies in their measurement. To solve this problem, the Hargreaves equation (HARG) is recognized by FAO and is often used. This equation is based on average, minimum and maximum air temperature and extraterrestrial radiation. It tends to overestimate ET0 in humid conditions and requires a local calibration. This paper examines the possibility for calibrating the HARG equation in Veneto region (north-eastern Italy) according to different criteria. For this study, full weather data sets of daily values collected along the period 1994–2006 from 35 agro-meteorological stations located in the Veneto plain were used. Ten stations were selected for calibration of the adjusted HARG equations, in order to represent the different areas of the plain, while the other 25 were used for validation.

[1]  Devendra M. Amatya,et al.  Comparison of methods for estimating REF-ET , 1995 .

[2]  George H. Hargreaves,et al.  Defining and Using Reference Evapotranspiration , 1994 .

[3]  Baryohay Davidoff,et al.  Comparison of Some Reference Evapotranspiration Equations for California , 2005 .

[4]  Juan Vicente Giráldez,et al.  Assessing Reference Evapotranspiration by the Hargreaves Method in Southern Spain , 2004 .

[5]  Slavisa Trajkovic,et al.  Hargreaves versus Penman-Monteith under Humid Conditions , 2007 .

[6]  Jerry L. Hatfield,et al.  Data quality checking for single station meteorological databases , 1994 .

[7]  C. Martinez,et al.  Estimating Reference Evapotranspiration with Minimum Data in Florida , 2010 .

[8]  George H. Hargreaves,et al.  Reference Crop Evapotranspiration from Temperature , 1985 .

[9]  Luis S. Pereira,et al.  Validation of the FAO methodology for computing ETo with limited data. Application to south Bulgaria , 2006 .

[10]  Sivaprakasam Subburayan.  Modified Hargreaves Equation for Estimation of ET 0 in a Hot and Humid Location in Tamilnadu State, India , 2011 .

[11]  George H. Hargreaves,et al.  Accuracy of Estimated Reference Crop Evapotranspiration , 1989 .

[12]  Richard G. Allen,et al.  Estimating Reference Evapotranspiration Under Inaccurate Data Conditions , 2002 .

[13]  I. Lorite,et al.  Regional calibration of Hargreaves equation for estimating reference ET in a semiarid environment , 2006 .

[14]  M. Jabloun,et al.  Evaluation of FAO-56 methodology for estimating reference evapotranspiration using limited climatic data Application to Tunisia , 2008 .

[15]  C. P. Jacovides,et al.  Statistical procedures for the evaluation of evapotranspiration computing models , 1995 .

[16]  F. Bautista,et al.  Calibration of the equations of Hargreaves and Thornthwaite to estimate the potential evapotranspiration in semi–arid and subhumid tropical climates for regional applications , 2009 .

[17]  L. S. Pereira,et al.  Crop evapotranspiration : guidelines for computing crop water requirements , 1998 .

[18]  R. G. Allen,et al.  Computation of ETo under Nonideal Conditions , 1997 .

[19]  R. Allen,et al.  History and Evaluation of Hargreaves Evapotranspiration Equation , 2003 .

[20]  Richard G. Allen,et al.  Comparison of Reference Evapotranspiration Calculations as Part of the ASCE Standardization Effort , 2003 .

[21]  Terry J. Gillespie,et al.  Evaluation of FAO Penman-Monteith and alternative methods for estimating reference evapotranspiration with missing data in Southern Ontario, Canada , 2010 .

[22]  R. E. Yoder,et al.  Evaluation Of Methods For Estimating Daily Reference Crop Evapotranspiration At A Site In The Humid Southeast United States , 2005 .