In this study, the Independent Uniformly Distributed Random Numbers (IUDRN) method as a hydrologic

synthetic data generation technique has been modified to simulate the streamflow in annual time scale.

A hybrid approach based on hydrological conditions-random number combination has been developed and

proposed. The three hydrologic conditions as wet, normal and dry conditions have been defined in one

third of each of random number that varies from 0 to 1. The annual mean values of 52 years discharge of

Arieh River situated in North of Neyshaboor in Khorassan province of Iran has been applied for validation

of proposed approach. The comparison between the results of two methods (IUDRN and proposed method)

shows that the error estimation has been reduced from 25% to 17%. This result indicates that new approach

(MIUDRN) can be applied to simulate the streamflow data with a high efficiency.