The muncipalities of Boqueirão and Patos, during the period from April 1, 2002 to February 28, 2003, were studied to evaluate the different methods of obtainig evaporation. Daily measurements of evaporation of the standard tank of 20 m² (WMO, 1996), and the Penman (1948); Linacre (1993); Snyder (1992); Kohler et al. (1955); Gangopadhyaya et al. (1966) and Hounam (1973) methods were used. The results indicated that the methods which use the relative humidity of air, wind speed and solar radiation presented the best performance. The method proposed by Snyder (1992) was the one that presented the best performance for the two studied areas, with the following relative error: -4.2% for Boqueirão and -3.3% for Patos. On the other hand, the method of Linacre (1993), which uses the daily air mean temperature obtained by the average of daily extreme values, presented the largest relative errors, -16.9% in Boqueirão city and(-1)8.2% in Patos city, showing that, if calibrated correctly, it can provide satisfactory results for the two studied areas.
solar radiation; relative humidity; wind; water resources
