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• Jenson, JW.
• Olsen, AE.
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• Jenson, JW.
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Water 2010, 2(1), 1-27; doi:10.3390/w2010001

Article

Estimating the Ground Water Resources of Atoll Islands

Ryan T. Bailey ^1,* , John W. Jenson ²  and Arne E. Olsen ²

¹ Department of Civil and Environmental Engineering, Colorado State University, 1372 Campus Delivery, Fort Collins, CO 80523, USA ² Water and Environmental Research Institute of the Western Pacific (WERI), University of Guam, Mangilao, Guam 96923, USA

* Author to whom correspondence should be addressed.

Received: 1 December 2009; in revised form: 4 January 2010 / Accepted: 8 January 2010 / Published: 14 January 2010

(This article belongs to the Special Issue Feature Papers)

Download PDF Full-Text [1727 KB, uploaded 14 January 2010 10:52 CET]

Abstract: Ground water resources of atolls, already minimal due to the small surface area and low elevation of the islands, are also subject to recurring, and sometimes devastating, droughts. As ground water resources become the sole fresh water source when rain catchment supplies are exhausted, it is critical to assess current groundwater resources and predict their depletion during drought conditions. Several published models, both analytical and empirical, are available to estimate the steady-state freshwater lens thickness of small oceanic islands. None fully incorporates unique shallow geologic characteristics of atoll islands, and none incorporates time-dependent processes. In this paper, we provide a review of these models, and then present a simple algebraic model, derived from results of a comprehensive numerical modeling study of steady-state atoll island aquifer dynamics, to predict the ground water response to changes in recharge on atoll islands. The model provides an estimate thickness of the freshwater lens as a function of annual rainfall rate, island width, Thurber Discontinuity depth, upper aquifer hydraulic conductivity, presence or absence of a confining reef flat plate, and in the case of drought, time. Results compare favorably with published atoll island lens thickness observations. The algebraic model is incorporated into a spreadsheet interface for use by island water resources managers.

Keywords: atoll; island hydrology; numerical modeling; drought

Supplementary Files

• Supplementary File 1:

  Atoll Freshwater Lens Tool (XLS, 157 KB)

• Supplementary File 2:

  Guide to Atoll Freshwater Lens Tool (PDF, 449 KB)

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