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Elucidaion of mantle structure of groundwater flow in freshwater lens by dense water-temperature observations

Research Project

Project/Area Number 26660194
Research Category

Grant-in-Aid for Challenging Exploratory Research

Allocation TypeMulti-year Fund
Research Field Rural environmental engineering/Planning
Research InstitutionNational Agriculture and Food Research Organization

Principal Investigator

Shirahata Katsushi  国立研究開発法人農業・食品産業技術総合研究機構, 農村工学研究部門地域資源工学研究領域, 主任研究員 (10648281)

Co-Investigator(Renkei-kenkyūsha) ISHIDA Satoshi  国立研究開発法人農業・食品産業技術総合研究機構, 農村工学研究部門 地域資源工学研究領域, ユニット長 (30414444)
Project Period (FY) 2014-04-01 – 2017-03-31
Project Status Completed (Fiscal Year 2016)
Budget Amount *help
¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2016: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2015: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2014: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Keywords地下水 / 淡水レンズ / 温度観測 / 降雨応答 / 潮汐応答 / 流動層 / 水温観測
Outline of Final Research Achievements

This study clarified by field observations that a freshwater lens is composed of two part, a core where the groundwater is stable and old, and a mantle where the flow is fast and the groundwater is young. On an island where a typical freshwater lens exists, three observations were made: dense temperature observations near the groundwater surface, multi-depth EC observations near the lower surface adjacent to blackish water, and observations using current meter in groundwater cropping out in a cave at the horizontal margin of the freshwater lens. They revealed that (1) large rainfall events occasionally produce a layer of groundwater just added to the freshwater lens with lower or higher temperature than the original groundwater part, (2) the lower surface of the freshwater lens fluctuates not only affected by the addition of rainwater, but also significantly by tides and others, and (3) at the horizontal margin the water flows periodically seaward and landward affected by tide.

Report

(4 results)
  • 2016 Annual Research Report   Final Research Report ( PDF )
  • 2015 Research-status Report
  • 2014 Research-status Report
  • Research Products

    (6 results)

All 2016 2015

All Journal Article (2 results) (of which Peer Reviewed: 2 results,  Acknowledgement Compliant: 2 results) Presentation (4 results) (of which Int'l Joint Research: 2 results)

  • [Journal Article] Digital Filters to Eliminate or Separate Tidal Components in Groundwater Observation Time-Series Data2016

    • Author(s)
      Katsushi Shirahata, Shuhei Yoshimoto, Takeo Tsuchihara, Satoshi Ishida
    • Journal Title

      Japan Agricultural Research Quarterly: JARQ

      Volume: 50 Issue: 3 Pages: 241-252

    • DOI

      10.6090/jarq.50.241

    • NAID

      130005254692

    • ISSN
      0021-3551, 2185-8896
    • Related Report
      2016 Annual Research Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Journal Article] Improvements in a simple harmonic analysis of groundwater time series based on error analysis on simulated data of specified lengths2016

    • Author(s)
      Katsushi Shirahata, Shuhei Yoshimoto, Takeo Tsuchihara, Satoshi Ishida
    • Journal Title

      Paddy and Water Environment

      Volume: - Issue: 1 Pages: 19-36

    • DOI

      10.1007/s10333-016-0525-3

    • Related Report
      2015 Research-status Report
    • Peer Reviewed / Acknowledgement Compliant
  • [Presentation] Digital filters for application to tidal groundwater time series2016

    • Author(s)
      Katsushi Shirahata, Shuhei Yoshimoto, Takeo Tsuchihara, Satsoshi Ishida
    • Organizer
      International Association of Hydrogeologists 43rd Congress
    • Place of Presentation
      Corum Conference Center (Montpellier, France)
    • Year and Date
      2016-09-28
    • Related Report
      2016 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 多深度自記温度観測による淡水レンズ地下水への降雨浸入深度把握の試み2016

    • Author(s)
      白旗克志,吉本周平,土原健雄,石田 聡
    • Organizer
      平成28年度農業農村工学会大会講演会
    • Place of Presentation
      ハーネル仙台(宮城県仙台市)
    • Year and Date
      2016-08-31
    • Related Report
      2016 Annual Research Report
  • [Presentation] Simple harmonic-analysis technique for separating out major tidal components in groundwater time-series data2015

    • Author(s)
      Katsushi Shirahata, Shuhei Yoshimoto, Takeo Tsuchihara, Satoshi Ishida
    • Organizer
      International Association of Hydrogeologists 42nd Congress
    • Place of Presentation
      Sapienza University of Rome (Rome, Italy)
    • Year and Date
      2015-09-17
    • Related Report
      2015 Research-status Report
    • Int'l Joint Research
  • [Presentation] 地下水位観測データから主要潮汐成分を分離する簡易調和解析法の適用性向上2015

    • Author(s)
      白旗克志,吉本周平,土原健雄,石田 聡
    • Organizer
      平成27 年度農業農村工学会大会講演会
    • Place of Presentation
      岡山大学津島キャンパス(岡山県岡山市)
    • Year and Date
      2015-09-02
    • Related Report
      2015 Research-status Report

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Published: 2014-04-04   Modified: 2018-03-22  

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