2024 Volume 37 Issue 4 Pages 351-358
Since the founding of Nagoya, the Horikawa River has been a symbol of the region. Improving the water quality of this artificial river with no self-flow has persisted as a challenge since the Meiji Era, when urbanization and industrialization rose to prominence. Among various methods, dilution by increasing the flow rate has been the most used method, with water quality improvement effectiveness confirmed recently from a three-year "social experiment" that began in 2007, followed by two-year observations. The outcomes of that effort are being inherited at the citizen level even now. As described herein, based on the continuity from the Kiso River, we examined methods to secure the flow rates in both the non-irrigated and irrigated periods using existing agricultural facilities of local resources, applying the 0.4 m3/s flow rate at the time of the "social experiment" as a benchmark.
The flow from the Kiso River to the Horikawa River has long been used for irrigation via the Kottsu-yōsui and Shin-kottsu-yōsui, with an accompanying history of use for navigation. Although this trial proposal has some potential for use as a practical example of the 'collaboration' of stakeholders in basin flood control, Ryūiki-chisui, it was also found to entail various challenges.
