Abstract
This study aimed to analyze safety levels of the water supply for irrigated rice paddy fields in the major river basins of Korea in the early modern era, and discussed its process of development in comparison with that of Japan. The area of rice paddy fields that can be irrigated in a river basin was estimated based on drought low flow discharges at different occurrence probabilities, and the safety level of the water supply for rice paddy fields was evaluated based on those occurrence probabilities. The results were as follows: 1) summer low flow discharges of Korean rivers are much smaller than those of Japan; 2) safety levels of the water supply for irrigated rice paddy fields were rather low at 40-90 % a year of the water shortage probability, except for the Han River, which means that by the early modern era, Korea had developed rice paddy fields to use all summer low flow discharges; 3) the high safety level in the Han River basin is presumably attributed to the difficulty of paddy field development because of frequent flood damage; and 4) the fact that the total amount of stable summer discharge in the river basin is much less than the required amount of water to support the strong rice demand in the era is believed to be a background factor that contributed to the excessive expansion of irrigated paddy fields as well as rain-fed paddies.
