Water balance in the Tedori River alluvial fan areas was analyzed for all components of the hydrological cycle based on the exchange of the channel-soil surface and aquifer horizon fractions with river water. The results were summarized on an annual basis, as well as for the irrigation and non-irrigation periods. The new findings of annual water balance are presented herein. The study area received 6.64 mm/day of precipitation annually and had an outflow of 2.53 mm/day as direct runoff, resulting in 4.11 mm/day of water being supplied to the soil surface. The canal-surface soil horizon fraction receives this 4.11 mm/day, as well as 9.12 mm/day intake water from the Head Works. Conversely, 2.45 mm/day is lost from evapotranspiration and another 3.21 mm/day is lost to percolation. Thus, surface runoff of 7.57 mm/day flows from the region to the Sea of Japan or drainage canals near the river mouth. In the aquifer horizon fraction, 3.21 mm/day of water is supplied from the canal-surface horizon fraction and 2.15 mm/day is supplied from the Tedori River, while 1.73 mm/day is obtained by groundwater extraction. Thus, 3.63 mm/day of groundwater flow out to the Sea of Japan or into downstream drainage canals. An outline of the water balance of the irrigation and non-irrigation period is also shown. Because various hydrological components are closely related to each other, planning and management of water resources for individual goals is not adequate, but requires the integrated aspect of water balance for sustainable water use.

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 Recently, many municipalities publish flood hazard maps. The manual that describes how to make a flood assumption zone map (basic map of flood hazard map) specifies the basic size of a ground height data to 50 m grid. However, this size is not enough to depict topography of an area, especially in lowland where a number of Japanese cities locates. From the above, this study aims to verify the accuracy of ground height data used in a flood hazard map and to clarify its effect to a flooding area or depth in Barajima district in Akita city, Akita prefecture. As a result, there were some differences between the Omono River flood assumption zone map and actual topography. Thus, the flood assumption zone in the map had a margin of error, and there was a possibility that the public misunderstood the flood risk.

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