The objective of this study is to develop a conceptual model to analyze the role of rice paddy fields in water management and to use the model to suggest an appropriate countermeasure for land development. Rice paddy fields are traditionally seen in East and South-East Asia, particularly in areas that have a considerable seasonal variation in rainfall resulting in flooding and drought. One of the advantages of these fields in East Asia is that the period of rainfall is similar to the period of the water demand of the rice paddy. In this study, the water management functions of rice paddy are evaluated using rainfall-storage-discharge (RSD) modeling. The RSD system is a type of onsite structure used for rainwater management. In this study, the area of the rice paddy is assumed to be 10,000 m(2), and the rice paddy is considered to perform the storage and catchment functions of a rainwater harvesting system. The RSD system can be used for analyzing the outflow rate according to the rice paddy area and the peak outflow curves for a 100-year period; further, the effectiveness of the RSD system in reducing the final water discharge rate through a rice paddy is evaluated.