[A-HW22] Material transportation and cycling in watershed ecosystems; from headwaters to coastal areas

[AHW22-08] Watershed Governance Based on Participation and Consensus for Sustainable Water Resource Use in Subtropical Islands -Contributing to the achievement of the SDGs-

*Jun Yasumoto¹, Ryuichi Shinjo², Bam H.N. Razafindrabe¹, Tomohiro Toki², Kazuko Sawada³, Takahiro Hosono⁴, Oktanius Richard Hermawan⁵, Shinji Nakaya⁶, Ryogo Takada⁷, Kei Nakagawa⁸, Makoto Kagabu⁸, Yasuhiro Tawara⁹, Atsuko Murai⁹, Yasumoto Ko¹⁰, Mizusawa Nanami¹⁰, Rio Maruyama¹⁰, Mina Yasumoto Hirose¹¹, Akira Iguchi¹², Mariko Iijima¹², KE-HAN SONG¹³, Masataka Aizawa¹³ (1.Department of Regional Agricultural Engineering, Faculty of Agriculture, University of the Ryukyus, 2.Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 3.Center for Strategic Research Projects, University of the Ryukyus, 4.Faculty of Advanced Science and Technology, Kumamoto University, 5.Graduate School of Science and Technology, Kumamoto University, 6.Fucalty of Engineering, Shinshu University, 7.Graduate School of Medicine, Science and Technology, Shinshu University, 8.Faculty of Environmental Science, Nagasaki University, 9.Geosphere Environmental Technology Corp., 10.School of Marine Biosciences, Kitasato University, 11.General Incorporated Association TROPICAL TECHNOLOGY PLUS, 12.National Institute of Advanced Industrial Science and Technology, 13.Graduate School of Engineering and Science, University of the Ryukyus)

Keywords:Watershed Governance, Sustainable Water Resource Use, Subtropical Islands

Water resources on subtropical islands are highly vulnerable to various stresses such as changes in industrial structure and climate change. Therefore, in recent years, depletion and pollution of water resources, namely groundwater has become major social issues. Pollution of groundwater degrades coral reef ecosystems through the water cycle and causes a decline in ecosystem services.
Two reasons appear to lead to this issue: [i] insufficient understanding and visualization of groundwater flow and transport processes of pollutants, and understanding of the mechanisms of coral reef ecosystem degradation, and [ii] lack of watershed governance for communicating and utilizing the scientific information in an easy-to-understand manner to the society.
The target area of this project is Yaese Town, located in Southern Okinawa. The main water resource in Yaese Town is groundwater, which is stored in the highly heterogeneous Ryukyu limestone. In Yaese Town, groundwater has been used as a valuable source of drinking water and water for irrigation. However, in recent years, groundwater pollution by nitrate nitrogen has become apparent, making related countermeasures an urgent issue.
For sustainable use of water resources in subtropical islands, it is necessary to quantitatively understand the flow of groundwater and the generation and transport processes of pollutants, as proposed in this technology seed. Furthermore, if we can visualize such scientific information, it will be possible to communicate the current status of water resources to local residents in an easy-to-understand manner. In addition, the sharing of such data will facilitate the planning and implementation of effective pollutant load reduction measures based on consensus building among stakeholders.
In this paper, we will briefly introduce the results of our research on [i] the understanding and visualization of groundwater flow and transport processes of pollutants, and the mechanisms of coral reef ecosystem degradation.