The aim of this work was to determine the probability of the occurrence of water deficits in Dourados, in Mato Grosso do Sul State, Brazil. The study was based on daily data of evapotranspiration and rainfall for a period of about 20 years. The reference evapotranspiration was estimated by the FAO Penman-Montheith method. The daily water deficit was determined through a sequential water balance. The total water deficit values of 10 day periods resulted in series that were adjusted to normal distribution. By means of the accumulated frequency function, values of water deficit were generated for return periods of 3, 4, 5, 10 and 15 years. The lowest and highest water deficit probabilities occur during April to July and August to September, respectively. Also, there is high water deficit probability occurrence during October to January, justifying technically the use of complementary irrigation in Dourados.
water balance; evapotranspiration; precipitation
