Time distribution models of intense and short rains are very important in hydrology and for extreme predictions in engineering projects. With this purpose, rain data of Piracicaba, SP, Brazil, from 1966 to 2000 were analyzed to establish time distribution models of 60 and 120 min intense rains, during the rainy season from October through March. Time distribution models were assessed by three intervals of twenty minutes duration, for 60 min rains and by four intervals of thirty minutes duration for 120 min rains. The prevailing precipitation model for both, 60 and 120 min rains was a negative exponential distribution, in 85.7 and 50.7% of cases, respectively. For 60 min rains fractions were distributed as 72.3, 21.4 and 6.2% of a total 20.7 mm precipitation. For 120 min rains, the result was 60.1, 25.2, 11.1 and 3.6% of a total 33.3 mm precipitation, in four successive intervals. Time distribution models for these rains were not affected by the amount of precipitation nor by their duration, in the intervals considered in this study.
intense rains; time distribution; models; probability
