This work was made aiming at testing the use of the Gamma Distribution model to estimate monthly rainfalls for the cities of Itapetinga and Vitória da Conquista in the Bahia state in Brazil. Two monthly rainfall data bases were used in the model construction. The first data base held information for the years from 1978 to 1997 for the city of Itapetinga. The second one held information from 1985 to 1995 for the city of Vitória da Conquista. Using each one of these data bases a and b parameters of the Gamma Distribution, for monthly rainfalls, were determinate. The adjusted distributions were used to estimate rainfall probabilities for each month of the year. The estimated values of the average monthly rainfall were compared to observed values for the period from 1998 to 2002 at Itapetinga and from 1995 to 2002 at Vitória da Conquista. The kolmogorov-Smirnov (2003) test was used in order to verify the adjustment of the estimated data to the observed values and the result was significant (p < 0.01). It was concluded that the values estimated, using the Gamma Distribution, showed a good adjustment in relation to the measured values for both cities, Itapetinga and Vitória da Conquista, and that this estimated values can be use in order to generate synthetic data for monthly rainfalls and monthly rainfalls probabilities in these places.
Probabilistic Models; Probability Rainfalls Distributions Adherence; Rain Statistics
