There are various methods to estimate the potential evapotranspiration (ETP). The simplified methods present limitations in relation to precision of the obtained results, while the more complex methods present the difficulty of availability of necessary data for calculation. In the present study the Thornthwaite and Camargo methods were compared with the Penman-Monteith method to verify the influence in obtaining daily ETP for the design of a drainage system, using the SISDRENA model. It is concluded that the differences among the methods did not affect significantly the calculation of economic drain spacing.
modeling; economic design; drain spacing
