Different from other natural hazards including floods, drought advances slowly and spreads widely, so that the preparedness is quite important and effective to mitigate the impacts from drought. Evaluation and forecast the status of drought for the present and future utilizing the meteorological scenario for agricultural drought can be useful to determine the agricultural drought mitigation for agriculture water resource management. This study calculated effective rainfall contributing to the runoff based on the historical rainfall data. The monthly effective rainfall for each return period computed using a frequency analysis, and determined the drought reference year for the determined meteorological scenario by each stage using the results of each return period.