Evapotranspiration, a phenomenon that affects and/or determines a number of processes such as pedological, climatic, hydrological, agrochemical, value is defined and determined by numerous methods and means, based on a variable number of factors, depending on the method applied. Results of the quantitative evaluation of evapotranspiration are of particular importance, given the fact that based on their follow is focused prevention or control of certain natural phenomena and / or anthropogenic. The main purpose of this study is to determine the reference evapotranspiration (ETo) by "classical" methods, but also by "modern" methods, applied using specialized software, to highlight quantitative and qualitative differences resulting from the application of the two types of methods. Also, the present paper aims to highlighting the importance of information systems in the calculation of ETo From the literature, we selected three "classical" methods for calculating the reference evapotranspiration, respectively: Thornthwaite method, Lawry-Johnson method and Ivanov method. The results will be compared with those obtained by the "computerized" FAO Penman-Monteith method, this method was applied using software CROPWAT 8.0. On the basis of the four methods of calculation, ETo was determined under the climatic conditions of the region Timisoara, different values are obtained depending on the applied calculation algorithm. Compared to conventional methods for calculating ETo, FAO Penman-Monteith method use, offers a number of advantages: increases calculation speed because it uses automatic means, reduce the calculation error, use a larger number of indicators thus increasing reliability of results, enables the graphical representation of the results. Compared with the FAO Penman-Monteith method, ETo values are generally lower when using the Ivanov method and are higher when using Lawry-Johnson method. Application Thornthwaite method provided results close to those obtained using FAO method, especially in the range from April to November - vegetation period of most crop plants. Therefore, the results of the determination reference evapotranspiration varies depending on the calculation algorithm applied and may thus to influence the subsequent analysis and estimates that this parameter is involved.

calculation, method, quantity, evapotranspiration.

Presentation: oral