STUDY OF THE RELATIONSHIP BETWEEN ANNUAL AND EXTREME DAILY RAINFALL IN ALGERIA

Maximum daily rainfalls and their frequency are of great interest to design engineers and water resource decision makers especially for urban hydrology tasks, civil engineering structures, and protection against floods. When rainfall data is unavailable, estimating the return period rainfall becomes a complicated task. The main purpose of the present study is to estimate the maximum rainfalls for any return period starting from the mean interannual rainfall at any location over the whole Algerian territory. The analysis of rainfall data has shown a good correlation between the mean interannual rainfall and the maximum daily one, which allows deriving a simple formula of the relationship between these two parameters. The formula was used to estimate the maximum rainfall for any return period using the statistical approach. It was found that the errors follow the normal distribution. The maximum errors do not exceed 15% for 100 years return period. The developed approach is very useful for ungauged basins, where estimating extreme rainfalls can be complicated, and can give acceptable maximum rainfall values to be used in flood forecasting or structure design.