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This paper deals with the trend for Penman-Monteith reference evapotranspiration, crop evapotranspiration and irrigation water requirements of some crops during the first decade of the 21st century versus the 20th century. These indices were calculated for three weather stations in various regions of southern Romania. Monthly distribution of reference evapotranspiration showed that for the first half of the year, these values were higher than the means of the 20th century. In the first decade of century XXI, crop evapotranspiration specifically increased in May, June and July, while the increase was negligible in August and it decreased in September. High crop evapotranspiration values were especially met for alfalfa and sugar beet. Irrigation water requirements increased in May and June. It had practically the same values in July and August, whereas irrigation application decreased in September. There is no need to irrigate during this month except in severe droughts.