Study on Saltification and Recovery of Freshwater Lens in Island Areas

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K07659
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Rural environmental engineering/Planning
• Research Institution: National Agriculture and Food Research Organization
• Principal Investigator: 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, ユニット長 (30414444)
• Co-Investigator(Renkei-kenkyūsha): 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・地下水資源ユニット, 主任研究員 (10648281) ; TSUCHIHARA Takeo 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・地下水資源ユニット, 上級研究員 (30399365) ; YOSHIMOTO Shuhei 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 (10435935)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 地下水 / 淡水レンズ / 塩水化 / 回復 / 揚水 / 取水 / アップコーニング

Outline of Final Research Achievements

Continuous observation of freshwater lens thickness by multiple EC meters was conducted in Taranaruma Island, Okinawa Prefecture, where freshwater lenses were developed in aquifers. In addition, we measured the fluctuation of electric conductivity in the groundwater and the surrounding observation hole during pumping and clarified the situation of upconing by pumping. From the groundwater flow model created based on the obtained results, the following was presumed. When intake of 100 m 3 / day is continued for 2 months, the EC of the groundwater pumped up in the center of the freshwater lens is less than 200 mS / m, but in the well far from the center the EC further rises. In well excavation, it is necessary to consider the permeability of the surrounding aquifer and the three-dimensional distribution of the freshwater lens.

Free Research Field

地下水