Japan Geoscience Union Meeting 2023

Presentation information

[E] Online Poster

A (Atmospheric and Hydrospheric Sciences ) » A-HW Hydrology & Water Environment

[A-HW18] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

Thu. May 25, 2023 10:45 AM - 12:15 PM Online Poster Zoom Room (5) (Online Poster)

convener:Takahiro Hosono(Faculty of Advanced Science and Technology, Kumamoto University), Syuhei Ban(The University of Shiga Prefecture), Mitsuyo Saito(Graduate School of Advanced Science and Engineering, Hiroshima University), Adina Paytan(University of California Santa Cruz)


On-site poster schedule(2023/5/26 17:15-18:45)

10:45 AM - 12:15 PM

[AHW18-P08] Spatial variation in groundwater discharge on a tidal flat in an island of western japan

*Qidi Gao1, Shin-ichi Onodera1, Mitsuyo Saito1, Yusuke Tomozawa1, Reiya Matsubara2 (1.Graduate School of Advanced Science and Engineering, Hiroshima University, 2.Faculty of Integrated Arts and Sciences, Hiroshima University)


Keywords:Submarine groundwater discharge, Spatial distribution, Tidal flat, Island

To manage and conserve the seagrass bed and ecosystem in tidal flats, this study examined to confirm spatial distribution in groundwater (SGD) on tidal flats with the area of around 100 m square in a small and steep island. Various groundwater and nutrient discharges were observed at the W and E sites. 1) Based on the water budget, the groundwater flux was estimated to be 8.68 m/yr or 23.9 mm/day in E, and 17.75 m/yr or 48.6 mm/day in W, respectively. 2) Spatial distributions of groundwater contribution ratio (%) in pore water at W was around 60% in average, which was 8 times of that in E site. 3) The NO3-N concentration in pore water at W site was about 30 times of that at E because of the low attenuation rate with high groundwater velocity. 4) The temporal variation in groundwater flux with tidal fluctuation indicated 2.5 m/day in maximum and -4.0 m/day in minimum. This huge difference between the average flux and maximum indicated also large seawater recirculation and heterogeneous distribution of SGD. This heterogeneous distribution at this tidal flat would contribute to the activity of seagrass and diversity of ecosystem.

Acknowledgment
This research was supported by JSPS Grant-in-Aid for Scientific Research (B) (No. 21H03650, PI: Mitsuyo Saito) and Fostering Joint International Research (A) (No. 20KK0262, PI: Mitsuyo Saito).