SPATIAL DISTRIBUTIONS IN GROUNDWATER DISCHARGE ON VARIOUS TIDAL FLATS IN A SMALL AND STEEP ISLAND, WESTERN JAPAN

Shingo Nozaki, Shin Ichi Onodera, Yusuke Tomozawa, Mitsuyo Saito

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)66-71
Number of pages6
JournalInternational Journal of GEOMATE
Volume20
Issue number81
DOIs
Publication statusPublished - May 2021

Keywords

  • Island
  • Spatial distribution
  • Submarine groundwater discharge
  • Tidal flat

ASJC Scopus subject areas

  • Environmental Engineering
  • Building and Construction
  • Geotechnical Engineering and Engineering Geology
  • Soil Science

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