Purpose: In this study, in order to find a way to minimize water supply shortage, reliability analysis of water supply was conducted by operating the Andong and the Imha Dam. The purpose is to find a way to minimize water shortage by the allocation distribution model from the reliability analysis results. Method: In this study, in order to analyze the water supply reliability of Andong and Imha Dam, using the Allocation rule presented by Park et al(2007), based on the planned water supply of Andong and Imha Dam for a total of 360 months from 1993 to 2022, analyzed. From the analysis results, the reliability of stable water supply was evaluated. Results: In the case of supplying the planned water supply of Andong and Imha Dam, the analysis result of Rule(B), which considers the ratio of the storage and inflow of the dam in the reservoir operation analysis result, showed that the shortage of Andong Dam occurred the most at 23 months, Regarding the number of shortages of control points, Rule(A), which considers only the storage capacity of the dam, was found to be short at 39 months, which is the largest number of shortages. As for the frequency standard reliability, Rule(B) showed the highest reliability of 90%, but in the case of quantitative reliability, the reliability was similar in all cases. Conclusion: In the water supply reliability, the reliability of stable water supply by supplying only the planned water supply amount is 94%, 93%, and 90% in Rule(B) of the allocation distribution model. 5% at the Andong dam, 7% at the Imha dam, and 10% at the control point. When water supply is evaluated with frequency reliability, it is judged that countermeasures for the shortfall are necessary. Next, in the case of quantitative reliability, when only the planned water supply was supplied, it was analyzed to be 95%, 94%, and 95% in all methods, so that the quantitative reliability was higher than the frequency reliability.