Rainfall infiltration processes must be properly modeled for short-and long-term high-precision prediction of regional groundwater flow. It was confirmed by numerical experiments that vertical seepage flow and interflow generated in the vadose zone are particularly important for short-term evaluation. In addition, the necessity of dividing the ground surface into high resolution to model the rainfall runoff process that occurs on the ground surface was also confirmed, but computer capacity is

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... mited at present. Therefore, since division into high resolution is not practical, it is necessary to devise measures to match the capacity. Furthermore, since the resolution of underground information is very coarse compared to information observed on the ground, it is necessary in the future to make efforts to construct a social mechanism for accumulating underground information and raise the resolution even a little.