Modified Holdridge method for evapotranspiration assessment
Abstract
Purpose. To assess the possibility and feasibility of using the Holdridge method to determine the annual potential evapotranspiration for determination of moisture deficit and adjustment of irrigation regimes using as the sample Kherson region by comparing the results of the assessment of the agrometeorological index with reference calculations in the FAO ET0 Calculator software by the Penman-Monteith algorithm (reference evapotranspiration), and suggest a possible option for recalculating potential evapotranspiration into a reference one. Methods. Calculation method for assessing evapotranspiration in the Kherson region for the annual period of 1973–2019 (by Holdridge using biotemperature and by Penman-Monteith methods); statistical analysis of the accuracy of calculations; linear regression method for trend building and linear forecasting; regression analysis for the development of a modified formula for calculating evapotranspiration from biotemperature. Results. It was found that the Holdridge method “as it is” results in the error of 37,03% in the estimation of evapotranspiration in comparison with the Penman-Monteith method. The trend and linear forecast for both methods of estimating evapotranspiration are identical, differing only in the curve steepness. The modified Holdridge equation reduces the error in calculating the reference evapotranspiration to 11,41%, which makes it possible to recommend it for the use in agricultural science and practice. Conclusions. Application of the Holdridge method “as it is” is advisable in climatology only but has limitations for agricultural use. The Holdridge equation, modified by the result of regression analysis of the data, can be recommended for a rough assessment of the annual reference evapotranspiration in the agricultural sector.
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