Freshwater Lens Observation: Case Study of Laura Island, Majuro Atoll, Republic of the Marshall Islands
Atolls are low-lying small islands with highly permeable ground that does not allow rivers and lakes to develop. As the water resources on these atolls basically rely on precipitation, groundwater becomes a very important water resource during droughts. Freshwater lenses develop as groundwater on relatively large atoll islands and play a key role in the stable water supply. Atoll islands in the Pacific Ocean sometimes suffer from drought due to El Nino. The global warming effects are noticeable, particularly on atoll islands. The Republic of the Marshall Islands in Oceania is burdened with the problems common to atoll islands. About half of its population lives in the capital, Majuro, and securing water resources for these people is a crucial issue. There is a freshwater lens on the largest, Laura Island, which serves as a water source for the downtown area. A serious drought that occurred in 1998 resulted in excessive water intake from the freshwater lens on Laura Island causing up-coning. Up-coning mixes saltwater into groundwater pumped from water-intake wells. Because up-coning makes the freshwater lens unusable, there was a need to investigate the freshwater lens on Laura Island. In this study, we observed the electrical conductivities of the groundwater at different depths in existing monitoring wells to determine the total storage volume of the freshwater lens on Laura Island from 2010 to 2013. Our results indicated that most of the groundwater that seeped into the freshwater lens had flowed out into the sea.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1339794Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 721
 Secretariat of the Pacific Community: Marshall Islands Population Atlas. http://www.spc.int/en/component/content/article/132-statistics-a-demography--new-sdp-releases/262-marshall-islands-population-atlas-.html, Viewed on October, 2014.
 Economic Policy, Planning, and Statistics Office, Office of the President: The RMI 2011 Census of Population and Housing Summary and Highlights Only, http://www.doi.gov/oia/reports/upload/RMI-2011-Census-Summary-Report-on-Population-and-Housing.pdf, Viewed on January, 2014.
 Federal Emergency Management Agency: http://www.fema.gov/disaster/1210, Viewed on November, 2013.
 K. T. Presley, “Effect of the 1998 Drought on the Freshwater Lens in the Laura Area, Majuro Atoll, Republic of the Marshall Islands,” USGS Scientific Investigation Report 2005-5098., 2005.
 I. White and T. Falkland, “Management of Freshwater Lenses on Small Pacific Islands,” Hydrogeology Journal, vol. 18, pp.227-246, 2010.
 S. Ishida, S. Yoshimoto, T. Kobayashi, K. Koda, T. Tsuchihara, and Y. Manpuku, “Sea Water Intrusion into Groundwater on Majuro Atoll, Republic of the Marshall Islands,” Japanese Society of Geotechnical Engineering, vol. 58, no. 5, pp.22-25, 2010.
 S. N. Hamlin and S. S. Anthony, “Ground-water resources of the Laura area, Majuro Atoll, Marshall Islands,” USGS Water-Resources Investigations Report 87-4047, 1987.
 S. S. Anthony, L. F. Peterson, T. F. Mackenzie & N. S. Hamlin, “Geohydrology of the Laura Freshwater Lens, Majuro Atoll: A Hydro-geochemical Approach.” GSA Bulletin, vol. 101, No. 8, pp.1066-1075, 1989.
 K. Koda and T. Kobayashi, “Sustainable Use of Laura Lens during Drought,” World Academy of Science, Engineering and Technology, International Science Index 108, International Journal of Biological, Biomolecular, Agricultural, Food and Biotechnological Engineering, vol. 9, no. 12, pp.1142 – 1145, 2015.