An EVI Model for Daily Rainfall Occurrence at Benin City, Nigeria

Abstract

By considering daily maximum rainfall values as random hydrologic variables, the Benin City rainfall occurrence from 1970 to 2004 (35 years) were analyzed in this study using Extreme value Type 1 (EVI) probability distribution in order to predict precipitation of desired return periods (T = 10, 100, 200, 500, 1000, 10,000yrs) which are to be used in watershed modeling to establish hydrologic design values for hydraulic structures in the catchment area. Our results indicate that EVI probability distribution model predicted rainfall values compares favourably with observed values with a percentage deviation ranging from -13.53% to 9.7% and that for the desired return periods, the predicted point rainfall values are 141.29mm, 193.04mm, 208.12mm, 228.19mm, 243.48mm and 294mm respectively and also that the maximum probable precipitation in the catchment is
526.75mm and therefore suggesting that the EVI probability distribution model isadequate for analyzing rainfall events in the catchment area but the greater the number of available past records, the greater will be the accuracy of prediction