Abstract

Actual evapotranspiration (ETa) is an important parameter in calculating the water consumption of crops, especially in the management and use of water for daily life activities, agricultural and forestry production. The article presents the results of determining the linear coefficient of the Priestley - Taylor model from a series of meteorological data directly measured at 11 hydro-meteorological stations in Hoa Binh and Son La provinces in the Northwest region of Vietnam in the period 2015-2021 and experimentally using Landsat 8 satellite image data combined with SEBAL and Prisetley -Taylor models with coefficients a, b proposed to calculate ETa value in Hoa Binh province on July 1^st, 2015 dated June 4^th, 2017 and August 18^th, 2021 to verify the appropriateness of the proposed coefficients a, b. The research results have determined that the coefficient a = 0.792, b = -0.026 for the Priestley - Taylor model is suitable for the topographic and climatic conditions in Hoa Binh province in the Northwest region of Vietnam. Directly measured evapotranspiration and evapotranspiration calculated by Priestley – Taylor model with coefficient a = 0.792, b = -0.026 with parameters calculated from Landsat 8 satellite image data shows the difference value The average deviation at 8 hydro-meteorological stations in Hoa Binh province at the time of July 1^st, 2015, June 4^th, 2017 and August 18^th, 2021 is 1.2 mm/day, 0.6 mm/day, and 0.8 mm/day and the mean square error of ±1.27 mm/day, ±1.15 mm/day and ±0.88 mm/day.