Stochastic analysis of the monthly water surpluses and deficits in Fortaleza, CE

Abstract

In order to quantify the probable water surpluses and deficits for the city of Fortaleza, CE, Brazil, it was carried out a probabilistic analysis, through the gamma distribution, of the monthly precipitations and evapotranspirations. For that purpose, it was used rainfall and evapotranspiration data for the period from 1971 to 2000. The correction of data was checked by the Kolmogorov-Smirnov goodness of fit test, at the 5% significance level. Next, it was made a water balance for each probabilistic level analyzed, for water available capacity of 125 mm. The estimated monthly water deficits, at the 75% probability level, were as follows: 92.2 mm in January; 10.7 mm in February; 8.2 mm in June; 47.1 mm in July; 89.4 mm in August; 121.6 mm in September; 140.9 mm in October; 153.8 mm in November; and 149.4 in December. It was observed monthly water surpluses, at the 75% probability level, only in the months of April (62.2 mm) and May (3.7 mm).