Northern Guam geospatial information serverNORTHERN GUAM LENS AQUIFERWhat is the NGLA?
The Northern Guam Lens Aquifer (NGLA) is the limestone bedrock that underlies the entire northern half of Guam and contains a large and permanent body of fresh groundwater. This body is approximately lens-shaped, being the thickest in the island's interior and thinnest along the island's perimeter. Because fresh water is less dense than seawater, this fresh groundwater lens floats upon saltwater that permeates the bedrock beneath it.
Where is the NGLA?
The Northern Guam Lens Aquifer encompasses all of northern Guam. It comprises of the limestone bedrock that is located north of the Pago-Adelup fault (geologic fault that separates the volcanic terrain of southern Guam from the limestone plateau in northern Guam). This body of limestone extends to the depth where it meets the volcanic units on top of which it sits. The volcanic units are the base (basement units) of the aquifer and are not a part of the aquifer itself. They are far less porous than the limestone and do not contain significant amounts of groundwater.
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