Reference evapotranspiration (ETo) is a key factor in determining the amount of water needed for crops, which is crucial to correct irrigation planning. FAO Penman-Monteith (EToPM) is among the most popular method to estimate ETo. Apparently sometimes it is difficult to compute ETo using Penman-Monteith due to challenges on data availability. FAO Penman-Monteith method requires many parameters (solar radiation, air temperature, wind speed and humidity), while Hargreaves-Samani method calculates ETo based on air temperature. Because Central Asia is a data limited region with weather stations unable to provide all required parameters for the PM method, this study aimed to estimate ETo using the Hargreaves and Samani (HS) method in Karshi Steppe, in Kashkadarya province, in southern Uzbekistan, based on data from 2011 to 2017. Reference evapotranspiration calculated by non-modified HS method is underestimated during the summer months. The reason for this underestimation might be higher air temperature and wind speed during these months. Therefore, the HS method in its original form cannot be used in our study area to estimate ETo. Modification of the EToHS, through application of a bias correction factor, had better performance and allowed improving the accuracy of the ETo calculation for this region. The calculated ETo values can inform decision making and management practices regarding water allocation, irrigation scheduling and crop selection in dry land regions of Amudarya river basin and the greater Central Asia area.
KeywordsReference EvapotranspirationHargreaves-SamaniPenman-MonteithAmudarya River Basin
United Nations Department of Economics and Social Affairs (UN DESA) (2013) World Population Prospects: The 2010 Revision, Volume II-Demographic Profiles. UN.
United Nations Environment Programme (UNEP) (2011) Environment and Security in the Amudarya Basin. Environment and Security. http://www.envsec.org/publications/AmuDarya-EN-Web.pdf
Agaltsceva, N.A. and Pak, A.V. (2007) Impact of Climate Change on River Flow of Aral Sea Basin. Climatic Scenarios, Impact of Climate Change. Bulletin, 44-52.
Chub, V.E. (2007) Climate Change and Its Impact on Hydrometeorological Processes, Agro-Climatic and Water Resources of the Republic of Uzbekistan. Center for Hydrometeorological Service under the Cabinet of Ministers of the Republic of Uzbekistan (Uzhydromet)/Scientific and Research Hydro-Meteorological Institute (NIGMI), Tashkent, Uzbekistan.
Spectorman, T.Y. and Petrova, E.V. (2008) Climate Scenarios for the Territory of Uzbekistan. Climate Scenarios, Climate Change Impact Assessment. Bulletin, 6, 14-21.
Aizen, V. and Aizen, E. (2009) Climate, Snow and Glaciers in High Central Asia in the Last 100 Years. http://www.sci.uidaho.edu/cae/index.html
Savoskul, O.S. and Smakhtin, V. (2013) Glacier Systems and Seasonal Snow Cover in Six Major Asian River Basins: Water Storage Properties under Changing Climate (Vol. 150). IWMI.
Allen, R.G., Morse, A. and Tasumi, M. (2003) Application of SEBAL for Western US Water Rights Regulation and Planning. ICID Workshop on Remote Sensing of ET for Large Regions, 17 September 2003.
Marek, T., Howell, T.A., Snyder, R.L., Porter, D. and Scherer, T. (2010) Crop Coefficient Development and Application to an Evapotranspiration Network. 5th National Decennial Irrigation Conference Proceedings, Phoenix, Arizona, 5-8 December 2010.
López-Urrea, R., de Santa Olalla, F.M., Fabeiro, C. and Moratalla, A. (2006) Testing evapotranspiration Equations Using Lysimeter Observations in a Semiarid Climate. Agricultural Water Management, 85, 15-26. https://doi.org/10.1016/j.agwat.2006.03.014
Jensen, M.E., Burman, R.D. and Allen, R.G. (1990) Evapotranspiration and Irrigation Water Requirements. Manuals and Reports on Engineering Practice. ASCE No. 70, New York.
Blaney, H.F. and Criddle, W.D. (1950) Determining Requirements Water in Irrigated Areas from Climatological and Irrigation Data. Washington Soil Conservation Service, 48.
Makkink, G.F. (1957) Testing the Penman Formula by Means of Lysimeters. Journal of the Institution of Water Engineers, 11, 277-288.
Priestley, C.H.B. and Taylor, R.J. (1972) On the Assessment of Surface Heat Flux and Evaporation Using Large-Scale Parameters. Monthly Weather Review, 100, 81-92. https://doi.org/10.1175/1520-0493(1972)100 2.3.CO;2
Hargreaves, G.H. and Samani, Z.A. (1985) Reference Crop Evapotranspiration from Temperature. Applied Engineering in Agriculture, 1, 96-99. https://doi.org/10.13031/2013.26773
Pandey, P.K., Dabral, P.P., and Pandey, V. (2016) Evaluation of Reference Evapotranspiration Methods for the Northeastern Region of India. International Soil and Water Conservation Research, 4, 52-63. https://doi.org/10.1016/j.iswcr.2016.02.003
Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998) Crop Evapotranspiration. FAO Irrigation and Drainage, Paper No. 56. Food and Agriculture Organization of the United Nations, Rome.
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. Agricultural Water Management, 97, 635-644. https://doi.org/10.1016/j.agwat.2009.12.001
Droogers, P. and Allen, R.G. (2002) Estimating Reference Evapotranspiration under Inaccurate Data Conditions. Irrigation and Drainage Systems, 16, 33-45. https://doi.org/10.1023/A:1015508322413
Hargreaves, G.H. and Allen, R.G. (2003) History and Evaluation of Hargreaves Evapotranspiration Equation. Journal of Irrigation and Drainage Engineering, 129, 53-63. https://doi.org/10.1061/(ASCE)0733-9437(2003)129:1(53)
Raziei, T. and Pereira, L.S. (2013) Estimation of ETo with Hargreaves-Samani and FAO-PM Temperature Methods for a Wide Range of Climates in Iran. Agricultural Water Management, 121, 1-18. https://doi.org/10.1016/j.agwat.2012.12.019
Almorox, J. and Grieser, J. (2016) Calibration of the Hargreaves-Samani Method for the Calculation of Reference Evapotranspiration in Different Köppen Climate Classes. Hydrology Research, 47, 521-531.
Cobaner, M., Citakoglu, H., Haktanir, T. and Kisi, O. (2017) Modifying Hargreaves-Samani Equation with Meteorological Variables for Estimation of Reference Evapotranspiration in Turkey. Hydrology Research, 48, 480-497. https://doi.org/10.2166/nh.2016.217
Ferreira, L.B., Cunha, F.F.D., Duarte, A.B., Sediyama, G.C. and Cecon, P.R. (2018) Calibration Methods for the Hargreaves-Samani Equation. Ciência e Agrotecnologia, 42, 104-114. https://doi.org/10.1590/1413-70542018421017517
Heydari, M.M. and Heydari, M. (2014) Calibration of Hargreaves-Samani Equation for Estimating Reference Evapotranspiration in Semiarid and Arid Regions. Archives of Agronomy and Soil Science, 60, 695-713. https://doi.org/10.1080/03650340.2013.808740
de Sousa Lima, J.R., Antonino, A.C.D., de Souza, E.S., Hammecker, C., Montenegro, S.M.G.L. and de Oliveira Lira, C.A.B. (2013) Calibration of Hargreaves-Samani Equation for Estimating Reference Evapotranspiration in Sub-Humid Region of Brazil. Journal of Water Resource and Protection, 5, 1-5. https://doi.org/10.4236/jwarp.2013.512A001
Morales-Salinas, L., Ortega-Farías, S., Riveros-Burgos, C., Neira-Román, J., Carrasco-Benavides, M. and López-Olivari, R. (2017) Monthly Calibration of Hargreaves-Samani Equation Using Remote Sensing and Topoclimatology in Central-Southern Chile. International Journal of Remote Sensing, 38, 7497-7513. https://doi.org/10.1080/01431161.2017.1323287
Landeras, G., Ortiz-Barredo, A. and López, J.J. (2008) Comparison of Artificial Neural Network Models and Empirical and Semi-Empirical Equations for Daily Reference Evapotranspiration Estimation in the Basque Country (Northern Spain). Agricultural Water Management, 95, 553-565. https://doi.org/10.1016/j.agwat.2007.12.011
State Committee of the Republic of Uzbekistan on Statistics (2016). https://stat.uz/en/
Allen, R., Pereira, L., Raes, D. and Smith, M. (1998) Crop Evapotranspiration: Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56, Rome.
Hargreaves, G.H. and Samani, Z.A. (1982) Estimating Potential Evapotranspiration. Journal of Irrigation and Drainage Engineering, 108, 223-230.
Teutschbein, C. and Seibert, J. (2012) Bias Correction of Regional Climate Model Simulations for Hydrological Climate-Change Impact Studies: Review and Evaluation of Different Methods. Journal of Hydrology, 456, 12-29. https://doi.org/10.1016/j.jhydrol.2012.05.052
Willmott, C.J. (1984) On the Evaluation of Model Performance in Physical Geography. In: Spatial Statistics and Models, Springer, Dordrecht, 443-600. https://doi.org/10.1007/978-94-017-3048-8_23
Awan, U.K., Tischbein, B., Conrad, C., Martius, C. and Hafeez, M. (2011) Remote sensing and Hydrological Measurements for Irrigation Performance Assessments in a Water User Association in the Lower Amu Darya River Basin. Water Resources Management, 25, 2467-2485. https://doi.org/10.1007/s11269-011-9821-2
Moeletsi, M.E., Walker, S. and Hamandawana, H. (2013) Comparison of the Hargreaves and Samani Equation and the Thornthwaite Equation for Estimating Dekadal Evapotranspiration in the Free State Province, South Africa. Physics and Chemistry of the Earth, Parts A/B/C, 66, 4-15. https://doi.org/10.1016/j.pce.2013.08.003
Stöckle, C.O., Kjelgaard, J. and Bellocchi, G. (2004) Evaluation of Estimated Weather data for Calculating Penman-Monteith Reference Crop Evapotranspiration. Irrigation Science, 23, 39-46. https://doi.org/10.1007/s00271-004-0091-0