Measurement of maximal évapotranspiration (ETM) of crops are compared with potential évapotranspiration (ETP) computations from Penman, Thornthwaite, Blaney — Criddle, Turc, Makkink. Correlations between ETM and solar radiation, insolation or pan evaporation are also calculated for 1966 — 1969 period. The validity of ETP estimates is discusscd either for planned regional irrigation or for water used by crops over short periods.