The objective of this work was to evaluate the limitations of a ten-day climatic water balance model to simulate irrigation in four different Paraná State regions. Sixty-eight water balance scenarios were tested to allow the relationship among crop evapotranspiration (ETc), probable precipitation at 75% level (P75%), soil available water capacity (AWC) and annual water deficiency (DEF). The results showed that: the model estimates its components better for greater values of available water (AW) in the soil; the ideal AWC value to process the irrigation analyses based on variations of ETo, Kc and ETc should be established in the model itself. However, if the condition "larger ten-day ETo < AW" of the period is valid, the water balance produces consistent results for 10 days periodicity.
simulation; AWC; available water; irrigation; agricultural irrigation